POLYTHIOL COMPOUNDS AND PROCESS FOR PREPARATION THEREOF

Abstract

The present application is directed to a polythiol compound obtainable independently from a) eugenol, b) gallic acid, c) the adduct of guaiacol and vanillin or d) resveratrol and, respectively, having the general Formula VIA, VIB, VIC or VID, wherein: R.sup.1 is a C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group, C.sub.2-C.sub.18 thioalkylene group, C.sub.6-C.sub.18 arylene or C.sub.7-C.sub.18 aralkylene group; and R.sup.2 is H or methyl.

##STR00001##

Claims

1: A polythiol compound having a Formula VIA, VIB or VIC: ##STR00032## wherein: R.sup.1 is a C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group, C.sub.2-C.sub.18 thioalkylene group, C.sub.6-C.sub.18 arylene or C.sub.7-C.sub.18 aralkylene group; and, R.sup.2 is H or methyl.

2: The compound according to claim 1, wherein: R.sup.1 is an unsubstituted C.sub.1-C.sub.12 alkylene group, preferably an unsubstituted C.sub.1-C.sub.4 alkylene group; and, R.sup.2 is H or Me.

3: The compound according to claim 1 which is selected from VIAa, VIBa or VICa: ##STR00033##

4: A process for preparing a compound having the general Formula VIA, VIB, VIC or VID ##STR00034## wherein: R.sup.1 is a C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group, C.sub.2-C.sub.18 thioalkylene group, C.sub.6-C.sub.18 arylene or C.sub.7-C.sub.18 aralkylene group; and, R.sup.2 is H or methyl, said process comprising providing a compound having the general Formula IA, IB, IC or ID: ##STR00035## and further comprising the steps of: a) reacting, in the presence of at least one base, said compound of general Formula IA, IB, IC or ID with a primary allyl compound (II) having the general Formula:
X(R.sup.1)C R.sup.2)?CH.sub.2(II) wherein: X is a halogen or an OC(50 O)OR? group; R? is a C.sub.1-C.sub.4 alkyl group; R.sup.1 is a C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group, C.sub.2-C.sub.18 thioalkylene group, C.sub.6-C.sub.18 arylene or C.sub.7-C.sub.18 aralkylene group; and, R.sup.2 is H or methyl to form, respectively, a compound of Formula IIIA, IIIB, IIIC or IIID: ##STR00036## b) reacting said compound of Formula IIIA, IIIB, IIIC or IIID with a thiol acid (IV) having the general Formula
R.sup.3C(50 O)SH(IV) wherein: R.sup.3 is C.sub.1-C.sub.6 alkyl, C.sub.6-C.sub.18 aryl, C.sub.7-C.sub.18 alkylaryl or C.sub.7-C.sub.18 aralkyl, to form, respectively, a thioester compound of Formula VA, VB, VC or VD: ##STR00037## and, c) deprotecting said thioester compound of Formula VA, VB, VC or VD to form, respectively, said polythiol compound of Formula VIA, VIB, VIC or VID.

5: The process according to claim 4, wherein said primary allyl compound (II) is characterized in that: R? is a C.sub.1-C.sub.2 alkyl; R.sup.1 is an unsubstituted C.sub.1-C.sub.12 alkylene group, preferably an unsubstituted C.sub.1-C.sub.4 alkylene group; and, R.sup.2 is H or Me.

6: The process according to claim 5, wherein said primary allyl compound (II) is selected from the group consisting of: 3-chloro-1-propene, 3-bromoprop-1-ene; 3-iodoprop-1-ene; methyl prop-2-enyl carbonate; and, ethyl prop-2-enyl carbonate.

7: The process according to claim 4, wherein said primary allyl compound (II) is reacted at a molar equivalency of from 1 to 2 relative to the number of moles of hydroxyl groups of Formula I.

8: The process according to claim 4, wherein said base is present in step a) in an amount of from 1 to 5 molar equivalents relative to the reactant compound IA, IB, IC or ID.

9: The process according to claim 4, wherein said base is selected from the group consisting of potassium carbonate, sodium carbonate and calcium carbonate.

10: The process according to claim 4, wherein said thiol acid (IV) is characterized in that: R.sup.3 is C.sub.1-C.sub.4 alkyl, C.sub.6 aryl, C.sub.7-C.sub.18 alkylaryl or C.sub.7-C.sub.18 aralkyl; and, wherein said thiol acid (IV) is selected from the group consisting of thioacetic acid, thiopropionic acid; thiobutyric acid, thioisobutyric acid, thiobenzoic acid, 2-methyl-thiobenzoic acid, 3-methyl-thiobenzoic acid, 4-methyl-thiobenzoic acid, 2,4-dimethyl-thiobenzoic acid and 3,5-dimethyl-thiobenzoic acid.

11: The process according to claim 4, wherein said thiol acid (IV) is reacted at a molar equivalency of from 1 to 2 relative to the allyl groups of said compound of Formula IIIA, IIIB, IIIC or IIID.

12: A process for preparing a compound having the general Formula VIB, VIC or VID ##STR00038## wherein: R.sup.1 is a C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group, C.sub.2-C.sub.18 thioalkylene group, C.sub.6-C.sub.18 arylene or C.sub.7-C.sub.18 aralkylene group; and, R.sup.2 is H or methyl, said process comprising providing a compound having the general Formula IB, IC or ID: ##STR00039## and further comprising the steps of: ?) reacting, in the presence of at least one base, said compound of general Formula IB, IC or ID with a thiolate ester compound having general Formula VII: ##STR00040## wherein: Y denotes a halogen; R.sup.1 is a C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group, C.sub.2-C.sub.18 thioalkylene group, C.sub.6-C.sub.18 arylene or C.sub.7-C.sub.18 aralkylene group; R.sup.2 is H or methyl; and, R.sup.3 is C.sub.1-C.sub.6 alkyl, C.sub.6-C.sub.18 aryl, C.sub.7-C.sub.18 alkylaryl or C.sub.7-C.sub.18 aralkyl, to form, respectively, a thioester compound of Formula VB, VC or VD: ##STR00041## and, ?) deprotecting said thioester compound of Formula VB, VC or VD to form, respectively, said polythiol compound of Formula VIB, VIC or VID.

13: The process according to claim 4, wherein said deprotection step (c), ?)) is performed by acid-catalysed or base-catalysed hydrolysis, wherein said acid or base catalyst is preferably present in said deprotection step (c), ?)) in an amount of from 0.05 to 0.25 moles per mole of said thioester of Formula VA, VB, VC or VD.

14: The process according to claim 13, wherein said deprotection step (c), ?)) is performed by base-catalysed hydrolysis and further wherein said base is selected from the group consisting of: pyridine; dimethylaminopyridine (DMAP); proline; triazabicyclodecene (TBD); diazabicycloundecene (DBU); hexahydro methyl pyrimido pyridine (MTBD); diazabicyclononane (DBN); tetramethylguanidine (TMG); and, triethylenediamine (TED, 1,4-diazabicyclo[2.2.2]octane).

15: A curable composition comprising the polythiol compound as defined in claim 1.

16: A curable composition comprising: a) at least one polythiol compound having the general Formula VIA, VIB, VIC or VID: ##STR00042## wherein: R.sup.1 is a C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group, C.sub.2-C.sub.18 thioalkylene group, C.sub.6-C.sub.18 arylene or C.sub.7-C.sub.18 aralkylene group; and, R.sup.2 is H or methyl; and, b) at least one thiol reactive compound, wherein the or each said thiol reactive compound has at least one functional group (F) selected from the group consisting of: epoxide groups; oxetane groups; cyclic carbonate groups; cyclic anhydride groups; 1-oxacycloalkan-2-one groups; ethylenically unsaturated groups; alkyne groups; and, isocyanate groups, wherein said thiol reactive compound b) is selected from the group consisting of include but are not limited to: epoxide compounds; ethylenically unsaturated compounds; epoxy (meth)acrylate compounds having at least one (meth)acrylate group and at least one epoxide group; and, polyisocyanates.

17: A compound of general Formula IIIC: ##STR00043## wherein: R.sup.1 is a C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group, C.sub.2-C.sub.18 thioalkylene group, C.sub.6-C.sub.18 arylene or C.sub.7-C.sub.18 aralkylene group; and, R.sup.2 is H or methyl. where R.sup.1 is an unsubstituted C.sub.1-C.sub.12 alkylene group, an unsubstituted C.sub.1-C.sub.4 alkylene group; and R.sup.2 is H or Me, or R.sup.1 is methylene; and R.sup.2 is H.

18: A compound having a formula VID: ##STR00044## wherein: R.sup.1 is a C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group, C.sub.2-C.sub.18 thioalkylene group, C.sub.6-C.sub.18 arylene or C.sub.7-C.sub.18 aralkylene group; and, R.sup.2 is H or methyl; where R.sup.1 is an unsubstituted C.sub.1-C.sub.12 alkylene group, an unsubstituted C.sub.1-C.sub.4 alkylene group; and R.sup.2 is H or Me, and R.sup.1 is not a methylene group when R.sup.2 is H.

Description

[0120] In the description below, reference will be made to the appended drawings in which:

[0121] FIG. 1 is illustrative of Step a) of the process of a first embodiment of the present disclosure;

[0122] FIG. 2 is illustrative of Step b) of the process of a first embodiment of the present disclosure;

[0123] FIG. 3 is illustrative of Step c) of the process of a first embodiment of the present disclosure; and,

[0124] FIG. 4 is illustrative of Step a) of the process of a second embodiment of the present disclosure.

[0125] FIG. 5 is illustrative of Steps aa) and bb) of the process of a third embodiment of the present disclosure.

[0126] The individual steps of the processes as defined above will be discussed in more detail herein below. If a chemical compound is referred to using both a chemical structure and a chemical name, and an ambiguity exists between the structure and the name, the structure predominates.

First Process Embodiment

[0127] This process embodiment is characterized in that the compound of formula VI is formed from a compound of formula I via an allyl functional intermediate (III). In the description of this embodiment below, where reference is made to Formulae I, III, V and VI, this is intended to denote, respectively, each of IA-ID, IIIA-IIID, VA-VD and VIA-VID.

Step a) Allylation

[0128] In this step of the described process, depicted in FIG. 1, there is provided the reaction of a compound of Formula I with a primary allyl compound (II) in the presence of at least one base. The primary allyl compound (II) corresponds to the allyl substituent that is to be introduced into the ally ether product (III) of this step. As denoted in the above reaction scheme, the primary allyl compound (II) has the general formula:

X(R.sup.1)C(R.sup.2)?CH.sub.2 [0129] wherein: X is a halogen or an OC(50 O)OR? group; [0130] R? is a C.sub.1-C.sub.4 alkyl group; [0131] R.sup.1 is a C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group, C.sub.2-C.sub.18 thioalkylene group, C.sub.6-C.sub.18 arylene or C.sub.7-C.sub.18 aralkylene group; and, [0132] R.sup.2 is H or methyl.

[0133] In most cases, allyl chloride (X=Cl) is favoured because of lower cost, but the allyl bromides and allyl iodides may be more reactive, particularly in the case of high molecular weight allyl compounds. In an initial statement of preference, it is preferred that: R? is a C.sub.1-C.sub.4 alkyl; R.sup.1 is an C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group or C.sub.2-C.sub.18 thioalkylene group; and, R.sup.2 is H or Me. In particular, it is preferred that: R? is a C.sub.1-C.sub.2 alkyl; R.sup.1 is an unsubstituted C.sub.1-C.sub.12 alkylene group; and, R.sup.2 is H or Me. In important embodiments: R.sup.1 is an unsubstituted C.sub.1-C.sub.4 alkylene group; and, R.sup.2 is H or Me.

[0134] Exemplary primary allyl halides in accordance with Formula II include: 3-chloro-1-propene (allyl chloride); 3-bromoprop-1-ene (allyl bromide); 3-iodoprop-1-ene (allyl iodide); 3-chloro-2-methyl-1-propene (methallyl chloride); 3-bromo-2-methyl-1-propene (methallyl bromide); 3-iodo-2-methyl-1-propene (methallyl iodide); 4-chloro-but-1-ene; 4-bromo-but-1-ene; 4-iodo-but-1-ene; 5-chloropent-1-ene; 5-bromopent-1-ene; 5-iodopent-1-ene; 6-chlorohex-1-ene; 6-bromohex-1-ene; 6-iodohex-1-ene; 7-chlorohept-1-ene; 7-bromohept-1-ene; 7-iodohept-1-ene; 8-chlorooct-1-ene; 8-bromooct-1-ene; 8-iodooct-1-ene; 10-chlorodec-1-ene; 10-bromodec-1-ene; 10-iododec-1-ene; 12-chlorododec-1-ene; 12-bromododec-1-ene; and, 12-iododoc-1-ene. Of the primary allyl halides, a preference for the use of 3-chloro-1-propene (allyl chloride); 3-bromoprop-1-ene (allyl bromide); 3-iodoprop-1-ene (allyl iodide) may be noted, and a particular preference for the use of 3-bromoprop-1-ene is acknowledged.

[0135] Exemplary further reactants in accordance with Formula Il include: methyl prop-2-enyl carbonate; ethyl prop-2-enyl carbonate; prop-2-enyl propyl carbonate; n-butyl prop-2-enyl carbonate; methyl 2-methylprop-2-enyl carbonate; and, ethyl 2-methylprop-2-enyl carbonate. Of these reactants, a preference may be noted for the use of methyl prop-2-enyl carbonate or ethyl prop-2-enyl carbonate.

[0136] It is intended that each hydroxyl group in the compound of Formula I be subjected to allylation and, as such, the primary allyl compound (II) should be present in at least a stoichiometric equivalent amount to the number of moles of said hydroxyl groups. The reaction mixture may, in particular, include said primary allyl compound (II) at a molar equivalency of from 1 to 2 relative to the number of moles of the hydroxyl groups of Formula I. Preferably, the allyl compound (II) is reacted at a molar equivalency of from 1.2 to 1.8 relative to the number of moles of the hydroxyl groups of Formula I.

[0137] The base which is present will react with the halogen acid liberated in the reaction and therefore should be present in at least the stoichiometric amount from that reaction. The reaction is operable in the presence of excess base however and therefore the base may be present in the reaction mixture in an amount of from 1 to 5 molar equivalents to the amount of compound (I). It is preferred that the base is present in an amount of from 1.5 to 3 molar equivalents or from 1.5 to 2.5 molar equivalents to the amount of compound (I).

[0138] Without intention to limit the present invention, the base should desirably consist of at least one compound selected from alkali metals, alkaline earth metals, alkali metal (C.sub.1-C.sub.4) alkoxides, alkaline earth metal (C.sub.1-C.sub.4) alkoxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal hydrides and alkaline earth metal hydrides. A preference for the use of at least one of potassium carbonate, sodium carbonate and calcium carbonate is noted.

[0139] In certain embodiments, the addition of a neutral alkali metal salt to the reaction mixture can have a positive effect on the yield of the allyation product. Exemplary alkali metal salts include: sulfates; sulfites; sulfides; halides; nitrates; nitrites; cyanides; borates; phosphates; monohydrogen phosphates; dihydrogen phosphates; phosphites; acid phosphites; and, carboxylates, such as acetates, formates, propionates, oxalates, tartrates, succinates, maleates and adipates.

[0140] A small amount of the neutral alkali metal saltfor instance from 0.01 to 0.05 moles per mole of compound (I)will have a yield-enhancing effect. The amount of said neutral salt should not however exceed the amount of basic catalyst included in the reaction mixture.

[0141] This step is still further performed in the presence of inert aprotic solvent. Examples of suitable aprotic solvents, which may be used alone or in combination, include but are not limited to: pentane; hexane; heptanes; cyclopentane; cyclohexane; cycloheptane; dimethylether; chloroform; dimethyl carbonate; ethylmethyl carbonate; diethyl carbonate; toluene; o-xylene; m-xylene; p-xylene; ethylbenzene; 2-propylbenzene (cumene); 2-isopropyltoluene (o-cymol); 3-isopropyltoluene (m-cymol); 4-isopropyltoluene (p-cymol); 1,3,5-trimethylbenzene (mesitylene); acetonitrile; N,N-di(C.sub.1-C.sub.4)alkylacylamides, such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc); hexamethylphosphoramide; N-methylpyrrolidone; pyridine; esters, such as (C.sub.1-C.sub.8)alkyl acetates, ethoxydiglycol acetate, dimethyl glutarate, dimethyl maleate, dipropyl oxalate, ethyl lactate, benzyl benzoate, butyloctyl benzoate and ethylhexyl benzoate; ketones, such as acetone, ethyl ketone, methyl ethyl ketone (2-butanone) and methyl isobutyl ketone; ethers, such as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF) and 1,2-dimethoxyethane; 1,3-dioxolane; dimethylsulfoxide (DMSO); and, dichloromethane (DCM).

[0142] Whilst it is not critical, it is preferred that the reaction of this step be performed under anhydrous conditions. Where necessary, exposure to atmospheric moisture may be avoided by providing the reaction vessel with an inert, dry gaseous blanket. Whilst dry nitrogen, helium and argon may be used as blanket gases, precaution should be used when common nitrogen gases are used as a blanket, because such nitrogen may not be dry enough on account of its susceptibility to moisture entrainment; the nitrogen may require an additional drying step before use herein.

[0143] The reaction need not be performed under reflux conditions but it is preferred to do so. Where reflux conditions are not used, the performance of the reaction at room temperature is not actually precluded but the use of elevated temperatures, for example at least 50? C. or at least 75? C., can drive the reaction. For an exothermic reaction, some cooling might however be required as the reaction progresses.

[0144] The process pressure is not critical: as such, the reaction can be run at sub-atmospheric, atmospheric, or super-atmospheric pressures but pressures at or slightly above atmospheric pressure are preferred. Mention in this regard may be made of pressures of from 50 to 200 kPa, for example from 100 to 200 kPa.

[0145] The progress of the above reaction may be monitored by known techniques of which mention may be made of .sup.1H NMR, Fourier Transform Infrared Spectroscopy, Ultra Performance Liquid Chromatography (UPLC) or thin layer chromatography (TLC). Upon completion of the reaction, the obtained mixture is filtered to remove solids: the solvent is removed from the filtrate to obtain the crude product.

[0146] The crude product may be used in the subsequent step of the process or, alternatively, the relevant compound may be purified using methods known in the art, including but not limited to solvent extraction, filtration and chromatography.

Step b) Thiol-ene Reaction

[0147] In this step, depicted in FIG. 2, the allyl functional compound (III) of step a) is reacted with a thiol acid (IV). The reactant thiol acid (IV) has the general formula:

R.sup.3C(50 O)SH(IV) [0148] wherein: R.sup.3 is C.sub.1-C.sub.6 alkyl, C.sub.6-C.sub.18 aryl, C.sub.7-C.sub.18 alkylaryl or C.sub.7-C.sub.18 aralkyl. [0149] Preferably R.sup.3 is C.sub.1-C.sub.4 alkyl, C.sub.6 aryl, C.sub.7-C.sub.18 alkylaryl or C.sub.7-C.sub.18 aralkyl.

[0150] Exemplary thiol acids include: thioacetic acid; thiopropionic acid; thiobutyric acid; thioisobutyric acid; thiocinnamic acid (3-phenylprop-2-enethioic S-acid); thiobenzoic acid; 2-methyl-thiobenzoic acid; 3-methyl-thiobenzoic acid; 4-methyl-thiobenzoic acid; 2,4-dimethyl-thiobenzoic acid; and, 3,5-dimethyl-thiobenzoic acid. A particular preference for the use of thioacetic acid or thiobenzoic acid may be mentioned.

[0151] Where it is intended that the thiol-ene should occur at each allyl group, the thiol acid (IV) should be present in the reaction mixture in at least a stoichiometric equivalent amount to the moles of said allyl groups. The reaction mixture may, in this instance, include said thiol acid (IV) at a molar equivalency of from 1 to 2 moles relative to said allyl groups. Preferably, the amount of thiol acid (IV) is within the range from 1.2 to 1.8 moles per mole of allyl groups.

[0152] Where the reactant includes more than one allyl group, the partial conversion of these groups may occur by using a sub-stoichiometric amount of thiol acid (IV) relative to the total number of moles of said allyl groups.

[0153] The skilled artisan will be aware that the reaction of thiol and -ene groups can occur under exposure to actinic irradiation and thus catalysts or accelerators may not strictly be required for this step of the process. However, this does not preclude the use in this step of a Michael addition catalyst, which herein refers to a compound capable of promoting a Michael addition reaction between the thiol acid and compounds of Formula III having terminal C?C unsaturation. Michael addition catalysts may be employed in an amount of from 0 to 5 wt. %, for example from 0.05 to 2 wt. %, based on the weight of said thiol acid.

[0154] Conventionally, Michael addition catalysts include amine-based catalysts, base catalysts and organometallic catalysts, which types may be used alone or in combination. Exemplary amine-based catalysts include: proline; triazabicyclodecene (TBD); diazabicycloundecene (DBU); hexahydro methyl pyrimido pyridine (MTBD); diazabicyclononane (DBN); tetramethylguanidine (TMG); and, triethylenediamine (TED, 1,4-diazabicyclo[2.2.2]octane). Examples of the base catalysts include: sodium methoxide; sodium ethoxide; potassium t-butoxide; potassium hydroxide; sodium hydroxide; sodium metal; lithium diisopropylamide (LDA); and, butyllithium. Exemplary organometallic catalysts include: ruthenium catalysts such as (cyclooctadiene) (cyclooctatriene) ruthenium and ruthenium hydride; iron catalysts such as iron (III) chloride and iron acetylacetonate; nickel catalysts such as nickel acetylacetonate, nickel acetate and nickel salicylaldehyde; copper catalysts; palladium catalysts; scandium catalysts; lanthanum catalysts; ytterbium catalysts; and, tin catalysts.

[0155] Whilst the thiol-ene reaction can be performed under Michael addition catalysis, these reactions can also be initiated by a free radical generating thermal initiator or a free radical photoinitiator. In this embodiment, the reaction mixture of this step may include from 0.1 to 1 wt. %, for example from 0.1 to 0.5 wt. % of at least one free radical initiator, based on the weight of said thiol acid.

[0156] Typically, free radical photoinitiators are divided into those that form radicals by cleavage, known as Norrish Type I, and those that form radicals by hydrogen abstraction, known as Norrish Type II. The Norrish Type Il photoinitiators require a hydrogen donor, which serves as the free radical source: as the initiation is based on a bimolecular reaction, the Norrrish Type II photoinitiators are generally slower than Norrish Type I photoinitiators which are based on the unimolecular formation of radicals. On the other hand, Norrish Type II photoinitiators possess better optical absorption properties in the near-UV spectroscopic region. The skilled artisan should be able to select an appropriate free radical photoinitiator based on the radiation being employed and the sensitivity of the photoinitiator(s) at that wavelength.

[0157] Preferred free radical photoinitiators are those selected from the group consisting of: benzoylphosphine oxides; aryl ketones; benzophenones; hydroxylated ketones; 1-hydroxyphenyl ketones; ketals; and, metallocenes. For completeness, the combination of two or more of these photoinitiators is not precluded in the present invention.

[0158] Particularly preferred free radical photoinitiators are those selected from the group consisting of: benzoin dimethyl ether; 1-hydroxycyclohexyl phenyl ketone; benzophenone; 4-chlorobenzophenone; 4-methylbenzophenone; 4-phenylbenzophenone; 4,4-bis(diethylamino) benzophenone; 4,4-bis(N,N-dimethylamino) benzophenone (Michler's ketone); isopropylthioxanthone; 2-hydroxy-2-methylpropiophenone (Daracur 1173); 2-methyl-4-(methylthio)-2-morpholinopropiophenone; methyl phenylglyoxylate; methyl 2-benzoylbenzoate; 2-ethylhexyl 4-(dimethylamino)benzoate; ethyl 4-(N,N-dimethylamino)benzoate; phenylbis (2,4,6-trimethylbenzoyl)phosphine oxide; diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide; and, ethyl phenyl (2,4,6-trimethylbenzoyl)phosphinate. Again, for surety, the combination of two or more of these photoinitiators is not precluded.

[0159] Where the reaction mixture of step b) comprises a free radical photoinitiator, irradiation of the reaction mixture generates the active species from the photoinitiator(s) which initiates the reactions. Once that species is generated, the chemistry is subject to the same rules of thermodynamics as any chemical reaction: the reaction rate may be accelerated by heat.

[0160] The energy source used to initiate the reaction of this embodiment of step b) will emit at least one of ultraviolet (UV) radiation, infrared (IR) radiation, visible light, X-rays, gamma rays, or electron beams (e-beam). The reaction may typically be activated in less than 2 minutes, and commonly between 0.1 and 100 secondsfor instance between 3 and 12 secondswhen irradiated using commercial curing equipment.

[0161] Irradiating ultraviolet light should typically have a wavelength of from 150 to 600 nm and preferably a wavelength of from 200 to 450 nm. Useful sources of UV light include, for instance, extra high-pressure mercury lamps, high pressure mercury lamps, medium pressure mercury lamps, low intensity fluorescent lamps, metal halide lamps, microwave powered lamps, xenon lamps, UV-LED lamps and laser beam sources such as excimer lasers and argon-ion lasers.

[0162] Where an e-beam is utilized to initiate the reaction, standard parameters for the operating device may be: an accelerating voltage of from 0.1 to 100 keV; a vacuum of from 10 to 10.sup.?3 Pa; an electron current of from 0.0001 to 1 ampere; and, power of from 0.1 watt to 1 kilowatt.

[0163] The amount of radiation necessary to sufficiently initiate the reaction will depend on a variety of factors including the angle of exposure to the radiation and the volume of the reaction mixture. Broadly, however, an applied dosage of from 5 to 5000 mJ/cm.sup.2 may be cited as being typical: applied dosages of from 50 to 500 mJ/cm.sup.2, such as from 50 to 200 mJ/cm.sup.2 may be considered highly effective.

[0164] As would be recognized by the skilled artisan, photosensitizers can be incorporated into the reaction mixture to improve the efficiency with which a photoinitiator uses the energy delivered. The term photosensitizer is used in accordance with its standard meaning to represent any substance that either increases the rate of photoinitiated polymerization or shifts the wavelength at which polymerization occurs. Photosensitizers should be used in an amount of from 0 to 25 wt. %, based on the weight of said free radical photoinitiator.

[0165] In lieu of using a free radical photoinitiator, radical generating thermal initiators may be employed in this step. Organic peroxides represent one exemplary class thereof: such organic peroxides may be selected, for example, from: cyclic peroxides; diacyl peroxides; dialkyl peroxides; hydroperoxides; peroxycarbonates; peroxydicarbonates; peroxyesters; and, peroxyketals.

[0166] While certain peroxidessuch as dialkyl peroxideshave been disclosed as useful initiators in inter alia U.S. Pat. No. 3,419,512 (Lees) and U.S. Pat. No. 3,479,246 (Stapleton) and indeed may have utility herein, hydroperoxides represent a preferred class of initiator. Further, whilst hydrogen peroxide itself may be used, the most desirable polymerization initiators are the organic hydroperoxides. For completeness, included within the definition of hydroperoxides are materials such as organic peroxides or organic peresters which decompose or hydrolyze to form organic hydroperoxides in situ: examples of such peroxides and peresters are cyclohexyl and hydroxycyclohexyl peroxide and t-butyl perbenzoate, respectively.

[0167] In an embodiment of the invention, the radical generating thermal initiator comprises or consists of at least one hydroperoxide compound represented by the formula:

R.sup.pOOH [0168] wherein: R.sup.p is an aliphatic or aromatic group containing up to 18 carbon atoms, and [0169] preferably wherein: R.sup.p is a C.sub.1-C.sub.12 alkyl, C.sub.6-C.sub.18 aryl or C.sub.7-C.sub.18 aralkyl group.

[0170] As exemplary peroxide initiators, which may be used alone or in combination, there may be mentioned: cumene hydroperoxide (CHP); para-menthane hydroperoxide; t-butyl hydroperoxide (TBH); t-butyl perbenzoate; t-butyl peroxy pivalate; di-t-butyl peroxide; t-butyl peroxy acetate; t-butyl peroxy-2-hexanoate; t-amyl hydroperoxide; 1,2,3,4-tetramethylbutyl hydroperoxide; benzoyl peroxide; dibenzoyl peroxide; 1,3-bis(t-butylperoxyisopropyl) benzene; diacetyl peroxide; butyl 4,4-bis(t-butylperoxy) valerate; p-chlorobenzoyl peroxide; t-butyl cumyl peroxide; di-t-butyl peroxide; dicumyl peroxide; 2,5-dimethyl-2,5-di-t-butylperoxyhexane; 2,5-dimethyl-2,5-di-t-butyl-peroxyhex-3-yne; and, 4-methyl-2,2-di-t-butylperoxypentane.

[0171] Without intention to limit the present disclosure, a further exemplary class of radical generating thermal initiators suitable for use in this reaction step are azo polymerization initiators, selected for example from: azo nitriles; azo esters; azo amides; azo amidines; azo imidazoline; and, macro azo initiators.

[0172] As representative examples of suitable azo polymerization initiators there may be mentioned: 2,2-azobis(2-methylbutyronitrile); 2,2-azobis(isobutyronitrile) (AIBN); 2,2-azobis(2,4-dimethylvaleronitrile); 2,2-azobis(4-methoxy-2,4-dimethylvaleronitrile); 1,1-azobis(cyclohexane-1-carbonitrile); 4,4-azobis(4-cyanovaleric acid); dimethyl 2,2-azobis(2-methylpropionate); 2,2-azobis[2-methyl-N-(2-hydroxyethyl)propionamide]; 2,2-azobis(N-butyl-2-methylpropionamide); 2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride; 2,2-azobis[2-(2-imidazolin-2-yl)propane]; 2,2-azobis(2-methylpropionamidine)dihydrochloride; 2,2-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]tetrahydrate; 4,4-azobis(4-cyanovaleric acid), polymer with alpha, omega-bis(3-aminopropyl)polydimethylsiloxane (VPS-1001, available from Wako Pure Chemical Industries, Ltd.); and, 4,4-azobis(4-cyanopentanoicacic).Math.polyethyleneglycol polymer (VPE-0201, available from Wako Pure Chemical Industries, Ltd.).

[0173] Redox free radical initiators are a combination of an oxidizing agent and a reducing agent and may also have utility in in step b) based on the thiol-ene. Suitable oxidizing agents may be selected from the group consisting of cyclic peroxides, diacyl peroxides, dialkyl peroxides, hydroperoxides, peroxycarbonates, peroxydicarbonates, peroxyesters and peroxyketals. The corresponding reducing agent may be selected from the group consisting of: alkali metal sulfites; alkali metal hydrogensulfites; alkali metal metabisulfites; formaldehyde sulfoxylates; alkali metal salts of aliphatic sulfinic acids; alkali metal hydrogensulfides; salts of polyvalent metals, in particular Co(II) salts and Fe(II) salts such iron(II) sulfate, iron(II) ammonium sulfate or iron(II) phosphate; dihydroxymaleic acid; benzoin; ascorbic acid; and, reducing saccharides, such as sorbose, glucose, fructose and/or dihydroxyacetone.

[0174] Step b) may be performed at a temperature of from 5 to 150? C., with a temperature in the range from 20 to 100? C. being more typical. The complete reaction may be accomplished in as little as one hour but, at lower reaction temperatures, as long as 24 hours may be required. Since the reaction is heterogeneous, agitation throughout the course of the reaction is important to maintain good physical contact between the reactant and to improve the reaction rate. Any means of agitation may be used.

[0175] The process pressure in step b) is not critical: as such, the reaction can be run at sub-atmospheric, atmospheric, or super-atmospheric pressures but pressures at or slightly above atmospheric pressure are preferred. Mention in this regard may be made of pressures of from 50 to 200 kPa, for example from 100 to 200 kPa.

[0176] The progress of the above reaction may be monitored by known techniques of which mention may be made of .sup.1H NMR, Fourier Transform Infrared Spectroscopy, Ultra Performance Liquid Chromatography (UPLC) or thin layer chromatography (TLC). Upon completion of the reaction, the unreacted thiol acid (IV) may be removed under reduced pressure to yield the crude thioester (V).

[0177] That crude product may be used in the subsequent step of the process or, alternatively, the relevant compound may be purified using methods known in the art, including but not limited to solvent extraction, filtration and chromatography.

Step c) Hydrolysis

[0178] In this step of the process, depicted in FIG. 3, the thioesters (V) are deprotected to yield the corresponding polythiol (VI). It is considered that this step may be performed using a reductive method wherein the thioester (IV) is reduced with LiAlHa with subsequent hydrolysis yielding the thiol (VI). However, in an important embodiment, this deprotection step is performed by acid-catalysed or base-catalysed hydrolysis.

[0179] In this embodiment, said acid or base catalyst should be present in the reaction mixture in an amount of from 0.05 to 0.25 moles per mole of said thioester (IV). As regards, acid-based hydrolysis, common acids include H.sub.2SO.sub.4 and HCl. For base-catalysed hydrolysis, organic base catalysts are preferred of which non-limiting examples include: pyridine; dimethylaminopyridine (DMAP); proline; triazabicyclodecene (TBD); diazabicycloundecene (DBU); hexahydro methyl pyrimido pyridine (MTBD); diazabicyclononane (DBN); tetramethylguanidine (TMG); and, triethylenediamine (TED, 1,4-diazabicyclo[2.2.2]octane).

[0180] The nucleophilic species (H) in the hydrolysis may be water. However, it is preferred that the nucleophile is a C.sub.1-C.sub.4 alkanol: a particular preference for the use of methanol (MeOH) may be noted. Wherein a C.sub.1-C.sub.4 alkanol is used the reaction products will be the thiol (VI) and a C.sub.1-C.sub.4 alkyl ester. That aside, nucleophile (H) should be present in at least a stoichiometric amount to the number of moles of thioester groups of compound (IV). An excess of the nucleophile may serve to drive the reaction to completion.

[0181] Whilst not strictly required, the described reaction of this step c) may be carried out in the presence of an inert aprotic solvent. The use of ether solvents is preferred of which mention may be made of: tetrahydrofuran (THF); 2-methyltetrahydrofuran (2-MeTHF); 1,2-dimethoxyethane; and, 1,3-dioxolane.

[0182] The reaction need not be performed under reflux conditions but it is preferred to do so. Where reflux conditions are not used, the performance of the reaction at room temperature is not actually precluded but the use of elevated temperatures, for example at least 50? C. or at least 75? C., can drive the reaction. Such elevated temperatures may indeed be required for acid-catalysed hydrolysis.

[0183] The process pressure is not critical: as such, the reaction can be run at sub-atmospheric, atmospheric, or super-atmospheric pressures but pressures at or slightly above atmospheric pressure are preferred. Mention in this regard may be made of pressures of from 50 to 200 kPa, for example from 100 to 200 kPa.

[0184] The progress of the above reaction may be monitored by known techniques of which mention may be made of .sup.1H NMR, Fourier Transform Infrared Spectroscopy, Ultra Performance Liquid Chromatography (UPLC) or thin layer chromatography (TLC). Upon completion of the reaction, the reaction mixture may be concentrated under evaporative conditionsto remove excess water, C.sub.1-C.sub.4 alkanol and/or solventto yield the crude polythiol (VI). That crude product may be purified using methods known in the art, including but not limited to solvent extraction, filtration and chromatography.

Second Process Embodiment

[0185] In this process embodiment, the intermediate compound of Formula VB, VC or VD is synthesized in a single step (a) from, respectively, the compound of Formula IB, IC or ID.

Step ?

[0186] In this step of the described process, depicted in FIG. 4, there is provided the reaction of a compound of Formula IB, IC or ID, in the presence of at least one base, with a thiolate ester having the general formula VII:

##STR00019## [0187] wherein: Y is a halogen; [0188] R.sup.1 is a C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group, C.sub.2-C.sub.18 thioalkylene, C.sub.6-C.sub.18 arylene group or C.sub.7-C.sub.18 aralkylene group; [0189] R.sup.2 is H or methyl; and, [0190] R.sup.3 is C.sub.1-C.sub.6 alkyl, C.sub.6-C.sub.18 aryl, C.sub.7-C.sub.18 alkylaryl or C.sub.7-C.sub.18 aralkyl.

[0191] In most cases, the chloride (Y=Cl) is favoured because of lower cost, but the bromides and iodides may be more reactive, particularly in the case of high molecular weight compounds. In an initial statement of preference, it is preferred that R.sup.1 is an C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group or C.sub.2-C.sub.18 thioalkylene group. More particularly, it is preferred that: R.sup.1 is an unsubstituted C.sub.1-C.sub.12 alkylene group; R.sup.2 is H or Me; and, R.sup.3 is C.sub.1-C.sub.4 alkyl, Co aryl, C.sub.7-C.sub.18 alkylaryl or C.sub.7-C.sub.18 aralkyl. In important embodiments: R.sup.1 is an unsubstituted C.sub.1-C.sub.4 alkylene group; R.sup.2 is H or Me; and, R.sup.3 is a C.sub.1-C.sub.4 alkyl.

[0192] Exemplary thiolate esters in accordance with formula VII include: S-(3-chloropropyl)ethanethioate; S-(3-bromopropyl)ethanethioate; and, S-(3-iodopropyl)ethanethioate.

[0193] It is intended that each hydroxyl group in the compound of Formula I be subjected to substitution and, as such, the thiolate ester compound (VII) should be present in at least a stoichiometric equivalent amount to the number of moles of said hydroxyl groups. The reaction mixture may, in particular, include said thiolate ester compound (VII) at a molar equivalency of from 1 to 2 relative to the number of moles of the hydroxyl groups of Formula I. Preferably, the thiolate ester compound (VII) is reacted at a molar equivalency of from 1.2 to 1.8 relative to the number of moles of the hydroxyl groups of Formula I.

[0194] The base which is present will react with the halogen acid liberated in the reaction and therefore should be present in at least the stoichiometric amount from that reaction. The reaction is operable in the presence of excess base however and therefore the base may be present in the reaction mixture in an amount of from 1 to 5 molar equivalents to the amount of compound (I). It is preferred that the base is present in an amount of from 1.5 to 3 molar equivalents or from 1.5 to 2.5 molar equivalents to the amount of compound (I).

[0195] Without intention to limit the present invention, the base should desirably consist of at least one compound selected from alkali metals, alkaline earth metals, alkali metal (C.sub.1-C.sub.4)alkoxides, alkaline earth metal (C.sub.1-C.sub.4) alkoxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal hydrides and alkaline earth metal hydrides. A preference for the use of at least one of potassium carbonate, sodium carbonate and calcium carbonate is noted.

[0196] In certain embodiments, the addition of a neutral alkali metal salt to the reaction mixture can have a positive effect on the yield of the thioester reaction product (V). Exemplary alkali metal salts include: sulfates; sulfites; sulfides; halides; nitrates; nitrites; cyanides; borates; phosphates; monohydrogen phosphates; dihydrogen phosphates; phosphites; acid phosphites; and, carboxylates, such as acetates, formates, propionates, oxalates, tartrates, succinates, maleates and adipates.

[0197] A small amount of the neutral alkali metal saltfor instance from 0.01 to 0.05 moles per mole of compound (I)will have a yield-enhancing effect. The amount of said neutral salt should not however exceed the amount of basic catalyst included in the reaction mixture.

[0198] This step is still further performed in the presence of inert aprotic solvent. Examples of suitable aprotic solvents, which may be used alone or in combination, include but are not limited to: pentane; hexane; heptanes; cyclopentane; cyclohexane; cycloheptane; dimethylether; chloroform; dimethyl carbonate; ethylmethyl carbonate; diethyl carbonate; toluene; o-xylene; m-xylene; p-xylene; ethylbenzene; 2-propylbenzene (cumene); 2-isopropyltoluene (o-cymol); 3-isopropyltoluene (m-cymol); 4-isopropyltoluene (p-cymol); 1,3,5-trimethylbenzene (mesitylene); acetonitrile; N,N-di(C.sub.1-C.sub.4)alkylacylamides, such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc); hexamethylphosphoramide; N-methylpyrrolidone; pyridine; esters, such as (C.sub.1-C.sub.8)alkyl acetates, ethoxydiglycol acetate, dimethyl glutarate, dimethyl maleate, dipropyl oxalate, ethyl lactate, benzyl benzoate, butyloctyl benzoate and ethylhexyl benzoate; ketones, such as acetone, ethyl ketone, methyl ethyl ketone (2-butanone) and methyl isobutyl ketone; ethers, such as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF) and 1,2-dimethoxyethane; 1,3-dioxolane; dimethylsulfoxide (DMSO); and, dichloromethane (DCM).

[0199] Whilst it is not critical, it is preferred that the reaction of this step be performed under anhydrous conditions. Where necessary, exposure to atmospheric moisture may be avoided by providing the reaction vessel with an inert, dry gaseous blanket. Whilst dry nitrogen, helium and argon may be used as blanket gases, precaution should be used when common nitrogen gases are used as a blanket, because such nitrogen may not be dry enough on account of its susceptibility to moisture entrainment; the nitrogen may require an additional drying step before use herein.

[0200] The reaction need not be performed under reflux conditions but it is preferred to do so. Where reflux conditions are not used, the performance of the reaction at 0? C. is not actually precluded but the use of elevated temperatures, for example at least 50? C. or at least 75? C., can drive the reaction. For an exothermic reaction, some cooling might however be required as the reaction progresses.

[0201] The process pressure in step a) is not critical: as such, the reaction can be run at sub-atmospheric, atmospheric, or super-atmospheric pressures but pressures at or slightly above atmospheric pressure are preferred. Mention in this regard may be made of pressures of from 50 to 200 kPa, for example from 100 to 200 kPa.

[0202] The progress of the above reaction may be monitored by known techniques of which mention may be made of .sup.1H NMR, Fourier Transform Infrared Spectroscopy, Ultra Performance Liquid Chromatography (UPLC) or thin layer chromatography (TLC). Upon completion of the reaction, excess base present in the reaction mixture may be quenched using an appropriate acid, such as hydrochloric acid. Moreover, the inert aprotic solvent may be removed under reduced pressure.

[0203] The crude product (VB, VC or VD) may then be separated from the reaction obtained mixture and may be used per se in the subsequent step of the process. Alternatively, the relevant compound may be purified using methods known in the art, including but not limited to solvent extraction, filtration and chromatography.

Step ?) Hydrolysis

[0204] This step of the processin which the thioester of formula VB, VC or VD is deprotected to yield, respectively, the corresponding polythiol (VIB, VIC or VID)is equivalent to step c) as described above and is depicted in FIG. 3.

Third Process Embodiment

[0205] In this process embodiment, the intermediate compound of Formula VA is formed from the compound of Formula IA in a two stage-process, as depicted in FIG. 5 appended hereto.

Step aa

[0206] In this step of the described process, depicted in FIG. 5, the compound of Formula IA is reacted, in the presence of at least one base, with a thiolate ester having the general Formula VII:

##STR00020## [0207] wherein: Y is a halogen; [0208] R.sup.1 is a C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group, C.sub.2-C.sub.18 thioalkylene, C.sub.6-C.sub.18 arylene group or C.sub.7-C.sub.18 aralkylene group; [0209] R.sup.2 is H or methyl; and, [0210] R.sup.3 is C.sub.1-C.sub.6 alkyl, C.sub.6-C.sub.18 aryl, C.sub.7-C.sub.18 alkylaryl or C.sub.7-C.sub.18 aralkyl, [0211] to form an intermediate compound of Formula VIIIA.

[0212] In most cases, the chloride (Y=Cl) is favoured because of lower cost, but the bromides and iodides may be more reactive, particularly in the case of high molecular weight compounds. In an initial statement of preference, it is preferred that R.sup.1 is an C.sub.1-C.sub.18 alkylene group, C.sub.2-C.sub.18 oxyalkylene group or C.sub.2-C.sub.18 thioalkylene group. More particularly, it is preferred that: R.sup.1 is an unsubstituted C.sub.1-C.sub.12 alkylene group; R.sup.2 is H or Me; and, R.sup.3 is C.sub.1-C.sub.4 alkyl, C.sub.6 aryl, C.sub.7-C.sub.18 alkylaryl or C.sub.7-C.sub.18 aralkyl. In important embodiments: R.sup.1 is an unsubstituted C.sub.1-C.sub.4 alkylene group; R.sup.2 is H or Me; and, R.sup.3 is a C.sub.1-C.sub.4 alkyl.

[0213] Exemplary thiolate esters in accordance with formula VII include: S-(3-chloropropyl)ethanethioate; S-(3-bromopropyl)ethanethioate; and, S-(3-iodopropyl)ethanethioate.

[0214] It is intended that each hydroxyl group in the compound of Formula IA be subjected to substitution and, as such, the thiolate ester compound (VII) should be present in at least a stoichiometric equivalent amount to the number of moles of said hydroxyl groups. The reaction mixture may, in particular, include said thiolate ester compound (VII) at a molar equivalency of from 1 to 2 relative to the number of moles of the hydroxyl groups of Formula I. Preferably, the thiolate ester compound (VII) is reacted at a molar equivalency of from 1.2 to 1.8 relative to the number of moles of the hydroxyl groups of Formula I.

[0215] The base which is present will react with the halogen acid liberated in the reaction and therefore should be present in at least the stoichiometric amount from that reaction. The reaction is operable in the presence of excess base however and therefore the base may be present in the reaction mixture in an amount of from 1 to 5 molar equivalents to the amount of compound (I). It is preferred that the base is present in an amount of from 1.5 to 3 molar equivalents or from 1.5 to 2.5 molar equivalents to the amount of compound (I).

[0216] Without intention to limit the present invention, the base should desirably consist of at least one compound selected from alkali metals, alkaline earth metals, alkali metal (C.sub.1-C.sub.4)alkoxides, alkaline earth metal (C.sub.1-C.sub.4) alkoxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal hydrides and alkaline earth metal hydrides. A preference for the use of at least one of potassium carbonate, sodium carbonate and calcium carbonate is noted.

[0217] In certain embodiments, the addition of a neutral alkali metal salt to the reaction mixture can have a positive effect on the yield of the thioester reaction product (V). Exemplary alkali metal salts include: sulfates; sulfites; sulfides; halides; nitrates; nitrites; cyanides; borates; phosphates; monohydrogen phosphates; dihydrogen phosphates; phosphites; acid phosphites; and, carboxylates, such as acetates, formates, propionates, oxalates, tartrates, succinates, maleates and adipates.

[0218] A small amount of the neutral alkali metal saltfor instance from 0.01 to 0.05 moles per mole of compound (I)will have a yield-enhancing effect. The amount of said neutral salt should not however exceed the amount of basic catalyst included in the reaction mixture.

[0219] This step is still further performed in the presence of inert aprotic solvent. Examples of suitable aprotic solvents, which may be used alone or in combination, include but are not limited to: pentane; hexane; heptanes; cyclopentane; cyclohexane; cycloheptane; dimethylether; chloroform; dimethyl carbonate; ethylmethyl carbonate; diethyl carbonate; toluene; o-xylene; m-xylene; p-xylene; ethylbenzene; 2-propylbenzene (cumene); 2-isopropyltoluene (o-cymol); 3-isopropyltoluene (m-cymol); 4-isopropyltoluene (p-cymol); 1,3,5-trimethylbenzene (mesitylene); acetonitrile; N,N-di(C.sub.1-C.sub.4)alkylacylamides, such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc); hexamethylphosphoramide; N-methylpyrrolidone; pyridine; esters, such as (C.sub.1-C.sub.8)alkyl acetates, ethoxydiglycol acetate, dimethyl glutarate, dimethyl maleate, dipropyl oxalate, ethyl lactate, benzyl benzoate, butyloctyl benzoate and ethylhexyl benzoate; ketones, such as acetone, ethyl ketone, methyl ethyl ketone (2-butanone) and methyl isobutyl ketone; ethers, such as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF) and 1,2-dimethoxyethane; 1,3-dioxolane; dimethylsulfoxide (DMSO); and, dichloromethane (DCM).

[0220] Whilst it is not critical, it is preferred that the reaction of this step be performed under anhydrous conditions. Where necessary, exposure to atmospheric moisture may be avoided by providing the reaction vessel with an inert, dry gaseous blanket. Whilst dry nitrogen, helium and argon may be used as blanket gases, precaution should be used when common nitrogen gases are used as a blanket, because such nitrogen may not be dry enough on account of its susceptibility to moisture entrainment; the nitrogen may require an additional drying step before use herein.

[0221] The reaction need not be performed under reflux conditions but it is preferred to do so. Where reflux conditions are not used, the performance of the reaction at 0? C. is not actually precluded but the use of elevated temperatures, for example at least 50? C. or at least 75? C., can drive the reaction. For an exothermic reaction, some cooling might however be required as the reaction progresses.

[0222] The process pressure in step aa) is not critical: as such, the reaction can be run at sub-atmospheric, atmospheric, or super-atmospheric pressures but pressures at or slightly above atmospheric pressure are preferred. Mention in this regard may be made of pressures of from 50 to 200 kPa, for example from 100 to 200 kPa.

[0223] The progress of the above reaction may be monitored by known techniques of which mention may be made of .sup.1H NMR, Fourier Transform Infrared Spectroscopy, Ultra Performance Liquid Chromatography (UPLC) or thin layer chromatography (TLC). At the completion of the reaction, the crude product (Formula VIII) may be used per se in the subsequent step of the process. In the alternative, the product may be separated from the reaction mixture and may be purified using methods known in the art, including but not limited to solvent extraction, filtration and chromatography. Such separation and purification should be preceded by the quenching of the reaction mixture using an appropriate acid, such as hydrochloric acid, and removal of the inert aprotic solvent under reduced pressure.

Step bb

[0224] In this step, the intermediate allyl functional compound (VIIIA) of step aa) is reacted with a thiol acid (IV) to yield the thioester of Formula VA. The reactant thiol acid (IV) has the general formula:

R.sup.3C(50 O)SH(IV) [0225] wherein: R.sup.3 is C.sub.1-C.sub.6 alkyl, C.sub.6-C.sub.18 aryl, C.sub.7-C.sub.18 alkylaryl or C.sub.7-C.sub.18 aralkyl. [0226] Preferably R.sup.3 is C.sub.1-C.sub.4 alkyl, C.sub.6 aryl, C.sub.7-C.sub.18 alkylaryl or C.sub.7-C.sub.18 aralkyl. R.sup.3 may be the same or different to that substituent of reactant VII as described above.

[0227] The reaction conditions described in step b) herein above are applicable to this reaction step bb) and will not be repeated here for the sake of conciseness.

Step cc) Hydrolysis

[0228] This step of the processin which the thioester (VA) is deprotected to yield the corresponding polythiol (VIA)is equivalent to step c) as described above and is depicted in FIG. 3.

Exemplary Compounds

[0229] In accordance with exemplary but non-limiting embodiments of the present invention, there are provided compounds represented by the Formula VIAa, VIBa and VICa below:

##STR00021##

[0230] In accordance with the above described reaction steps, these compounds may be formed from Compounds IA, IB and IC: [0231] i) in accordance with the first process embodiment, through using an allylation reagent (II) in which R.sup.1=CH.sub.2 and R.sup.2=H, in particular allyl bromide (X=Br) or ethyl prop-2-enyl carbonate (X is OC?O)OEt); and, the thiol acid thioacetic acid (R.sup.3=Me); [0232] ii) in accordance with the second process embodiment and having regard to compounds VIBa and VICa, through using a thiolate ester reagent (VII) in which Y=halogen, R.sup.3=CH.sub.2, R.sup.2=H and R.sup.3 is a C.sub.1-C.sub.4 alkyl; or, [0233] iii) in accordance with the third process embodiment and having regard to compound VIAa, through using a thiolate ester reagent (VII) in which Y=halogen, R.sup.1=CH.sub.2, R.sup.2=H and R.sup.3 is a C.sub.1-C.sub.4 alkyl and, subsequently, as the thiol acid reagent, thioacetic acid (R.sup.3=Me).

Compositions Containing the Thiol Compounds of the Present Invention

[0234] The polythiol compounds of the present disclosure are considered to be versatile and thereby have a plethora of uses. It is certainly anticipated that the thiol compounds per se may find utility as a curative or otherwise reactive component of an one (1K) or two (2K) component curable composition. Such an one (1K) or two (2K) component curable composition may, in particular, be a coating, adhesive or sealant composition. It is also not precluded that the one (1K) or two (2K) composition may be a dual cure composition.

[0235] In an important embodiment of the disclosure, the curable composition comprises: [0236] a) at least one polythiol as described hereinabove; and, [0237] b) at least one thiol reactive compound, wherein the or each said thiol reactive compound has at least one functional group (F) selected from the group consisting of: epoxide groups; oxetane groups; cyclic carbonate groups; cyclic anhydride groups; 1-oxacycloalkan-2-one groups; ethylenically unsaturated groups; alkyne groups; and, isocyanate groups.

[0238] For surety, it is stated that a given thiol reactive compound b) may have more than one different functional group in its structure: it may, for instance, have an epoxide group and a (meth) acrylate group. Exemplary thiol reactive compounds b) include but are not limited to: epoxide compounds; ethylenically unsaturated compounds; epoxy (meth) acrylate compounds having at least one (meth) acrylate group and at least one epoxide group; and, polyisocyanates. As regards ethylenically unsaturated groups, note may be made of the instructive reference Hoyle et al. Thiol-Enes: Chemistry of the Past with Promise for the Future J. Polym. Sci. A Polym. Chem. 2004, 42:5301 (2004).

[0239] No particular limitation is imposed on the number of functional groups (F) possessed by the thiol reactive compound(s): compounds having 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 functional groups may be used, for instance. Moreover, the thiol reactive compound(s) can be a low-molecular-weight substancepossessing a number average molecular weight (Mn) of less than 500 g/molor an oligomeric or polymeric substance that has a number average molecular weight (Mn) of at least 500 g/mol. And, of course, mixtures of thiol reactive compounds b) may be used.

[0240] The following examples are illustrative of the present invention and are not intended to limit the scope of the invention in any way.

EXAMPLES

[0241] The following commercial compounds are used in the Example: [0242] Thioacetic acid: Available from Tokyo Chemical Industry Co., Ltd. [0243] Azobisisobutyronitrile (AIBN): Available from Sigma-Aldrich [0244] Triazabicyclodecene (TBD): Available from Sigma-Aldrich

Example 1: Synthesis of Compound VIAa

[0245] ##STR00022##

Step a): Allylation

[0246] ##STR00023##

[0247] A suspension of eugenol (9.8 g, 60 mmol), K.sub.2CO.sub.3 (16.6 g, 120 mmol) and allyl bromide (7.8 mL, 90 mmol) in acetone (140 mL) was stirred at 60? C. for 12 hours. After cooling to ambient temperature, the suspension was filtered through a Celite to remove insoluble solids. The filtrate was concentrated on a rotary evaporator and the obtained crude product was purified by silica gel flash column chromatography eluting with a mixture of cyclohexane (90 wt. %) and ethyl acetate (10 wt. %) to give the allylated product (IIIAa) as a pale yellow liquid in 99% yield.

[0248] .sup.1H NMR (300 MHz, CDCl.sub.3) ?: 6.82 (d, J=8.0 Hz, 1H), 6.75-6.65 (m, 2H), 6.22-5.84 (m, 2H), 5.39 (dq, J=17.2, 1.6 Hz, 1H), 5.27 (dq, J=10.5, 1.4 Hz, 1H), 5.18-5.00 (m, 2H), 4.59 (dt, J=5.4, 1.5 Hz, 2H), 3.87 (s, 3H), 3.34 (dtt, J=6.7, 1.3, 0.6 Hz, 2H).

[0249] .sup.13C NMR (75 MHz, CDCl.sub.3) ?: 149.51, 146.44, 137.75, 133.68, 133.18, 120.44, 117.88, 115.72, 113.73, 112.35, 77.16, 70.13, 55.96, 39.92.

[0250] ESI-MS (m/z) calculated for C.sub.13H.sub.16O.sub.2: 204.1144, found: 204.1142.

Steps b) and c) Thiol-ene Reaction Followed by Hydrolysis

[0251] ##STR00024##

[0252] The above obtained allylated product (IIIAa: 6.1 g, 30 mmol) was reacted with thioacetic acid (7.5 ml, 45 mmol) in the presence of azobisisobutyronitrile (AIBN, 300 mg, 1.8 mmol) at 80? C. for 20 hours. Unreacted thioacetic acid was removed under reduced pressure to give crude dithioester intermediate.

[0253] The obtained crude dithioester was hydrolyzed in methanol (83 ml) at 70? C. for 15 hours in the presence of triazabicyclodecene (TBD, 2.4 g, 9.0 mmol). The reaction mixture was concentrated on a rotary evaporator and the residual oil was dissolved in dichloromethane to be washed with water. After drying the organic phase over MgSO.sub.4 and removal of volatiles, the desired product (VIAa) was obtained as a yellow liquid in 93%.

[0254] .sup.1H NMR (300 MHz, CDCl.sub.3) ?: 6.87-6.77 (m, 1H), 6.75-6.62 (m, 2H), 4.19-3.97 (m, 2H), 3.84 (s, 3H), 2.81-2.60 (m, 4H), 2.60-2.45 (m, 2H), 2.10 (tt, J=7.0, 6.1 Hz, 2H), 2.00-1.81 (m, 2H), 1.44 (t, J=8.1 Hz, 1H), 1.39-1.31 (m, 1H).

[0255] .sup.13C NMR (75 MHz, CDCl.sub.3) ?: 149.54, 146.58, 134.51, 120.44, 113.76, 112.39, 77.16, 67.21, 55.99, 35.65, 33.99, 33.45, 24.01, 21.43.

[0256] ESI-MS (m/z) calculated for C.sub.13H.sub.20O.sub.2S.sub.2: 272.0899, found: 272.0897.

Example 2: Synthesis of Compound VIBa

[0257] ##STR00025##

Step a) Allylation to Yield Allyl-3,4,5-tris (allyloxy)benzoate

[0258] ##STR00026##

[0259] A 500 mL two-necked flask equipped with a septum cap and magnetic stirring bar was charged with 200 mL of DMF and gallic acid (60 mmol, 10.21 g). The solution was cooled with an ice bath and potassium carbonate (240 mmol, 33.17 g) was added. After five minutes, allyl bromide (240 mmol, 21.17 ml) was added dropwise using a dropping funnel. The solution was stirred for 30 minutes at 0? C. and then at 25? C. for a period 48 hours. 200 ml of water was added and the aqueous phase was extracted with 3?100 ml of ethyl acetate. The organic phase was washed with 100 mL of brine then dried over MgSO.sub.4 and vacuum concentrated. The residue was purified by silica gel chromatography (CH: EtOAc, 90:10) to furnish the product (IIIBa) as a pale yellow liquid (Isolated Yield: 82%).

[0260] .sup.1H NMR (300 MHz, DMSO-d6) ?: 7.25 (s, 2H), 6.21-5.86 (m, 4H), 5.43 (dq, J=10.0, 1.7 Hz, 2H), 5.39 (q, J=1.8 Hz, 1H), 5.36 (qd, J=1.6, 0.5 Hz, 1H), 5.32-5.27 (m, 2H), 5.26-5.24 (m, 1H), 5.17 (ddt, J=10.4, 1.9, 1.3 Hz, 1H), 4.78 (dt, J=5.4, 1.5 Hz, 2H), 4.63 (dt, J=5.0, 1.6 Hz, 4H), 4.54 (dt, J=5.7, 1.4 Hz, 2H).

[0261] .sup.13C NMR (75 MHz, DMSO) ?: 164.85, 151.90, 141.13, 134.35, 133.39, 132.61, 124.55, 117.76, 117.35, 117.15, 107.98, 73.15, 69.14, 65.11, 39.52.

[0262] ESI-MS (m/z) calculated for C.sub.19H.sub.22O.sub.5: 331.1545, found: 331.1551.

Steps b) and c) Thiol-ene Reaction Followed by Hydrolysis

[0263] ##STR00027##

[0264] In a first step, Allyl-3,4,5-tris (allyloxy)benzoate (22.3 g, 68 mmol) was reacted with thioacetic acid (29 ml, 408 mmol,) and AIBN (2.23 g, 13.6 mmol,) by stirring the mixture at 80? C. for 20 h. Subsequently, unreacted thioacetic acid was removed under reduced pressure. The compound was extracted with DCM: 3?H.sub.2O. The organic phase was separated and dried over MgSO.sub.4. Volatiles were removed to obtain the product.

[0265] For the second step, the compound was dissolved in 400 ml of dry THF and 1.1 equiv. of Conc. HCl (37.8 g) in 90 ml of dry MeOH was added to the solution. The mixture was degassed for 10 min under Ar and the solution was stirred at 70? C. for 22 h. Finally, the solvent was removed, and tetra-thiol was extracted with DCM: 3?H.sub.2O. The organic phase was separated and dried over MgSO.sub.4. Volatiles were removed to obtain the final product. Further purification was done doing vacuum distillation at 120? C. with 5?10.sup.?2 mbar. The isolated yield was 75%.

[0266] .sup.1H NMR (300 MHz, CDCl.sub.3) ?: 7.28 (s, 2H), 4.42 (t, J=6.2 Hz, 2H), 4.13 (dt, J=10.8, 5.8 Hz, 6H), 2.88-2.60 (m, 8H), 2.08 (dp, J=26.9, 6.6 Hz, 8H), 1.45 (q, J=8.1 Hz, 4H).

[0267] .sup.13C NMR (101 MHz, CDCl.sub.3) ?: 166.15, 152.59, 141.94, 125.32, 108.23, 77.16, 71.12, 67.03, 63.32, 34.40, 33.35, 33.02, 21.38.

[0268] ESI-MS (m/z) calculated for C.sub.19H.sub.30O.sub.5S.sub.4[M+Na].sup.+: 489.0873, found: 489.0886.

[0269] EA: calculated for C.sub.19H.sub.30O.sub.5S.sub.4: C, 48.90; H, 6.48; S, 27.48. found: C, 48.02; H, 7.32; S, 26.96.

Example 3: Synthesis of Compound VICa

[0270] ##STR00028##

Pre-Step: Preparation of tris(3-methoxy-4-hydroxyphenyl)methane (ICa)

[0271] ##STR00029##

[0272] Under magnetic stirring, vanillin (76.1 g, 1 equiv.) and guaiacol (310.4 g, 5 equiv.) were charged into a 1 L single-necked round-bottom flask. Upon complete dissolution of vanillin, zinc chloride (ZnCl.sub.2, 6.8 g, 0.1 equiv.) and p-toluenesulfonic acid (PTSA, 9.5 g, 0.1 equiv.) were added. The mixture was kept in open air at 50? C. for 5 days. The progress of the reaction was monitored by thin-layer chromatography (TLC) plate in ethyl acetate/hexane (v/v=1/1) solution. Next, the mixture was washed with hot water (>70? C.) three times to remove the catalysts (ZnCl.sub.2 and PTSA). The unreacted guaiacol was removed and recycled using a rotary evaporator under reduced pressure at 140? C. The received viscous liquid was placed in vacuum oven at 90? C. for 12 hours. The crude product (ICa) was further purified by crystallization in chloroform: the obtained triphenol compound was a red powder (Isolated Yield: 63%). Based on the .sup.1H NMR there is one molecule of chloroform as a crystallization molecule.

[0273] .sup.1H NMR (300 MHz, DMSO-d.sub.6) ?: 8.76 (s, 3H, OH), 6.74-6.60 (m, 6H, ArH), 6.44 (dd, J=8.3, 1.9 Hz, 3H, ArH), 5.23 (s, 1H, Ar.sub.3CH), 3.65 (s, 9H, CH.sub.3).

[0274] .sup.13C NMR (75 MHz, CDCl.sub.3) ?: 147.21, ArC, 144.67, ArC, 135.72, ArC, 121.19, ArC, 115.10, ArC, 113.27, ArC, 55.58, Ar.sub.3C, 54.66, CH.sub.3, 39.52.

[0275] ESI-MS (m/z) calculated for C.sub.22H.sub.22O.sub.6: 382.1410, found: 382.1409.

Step a) Allylation to tris(4-(allyloxy)-3-methoxyphenyl)methane

[0276] ##STR00030##

[0277] A suspension of triphenol (15.3 g, 40 mmol), K.sub.2CO.sub.3 (28.193 g, 204 mmol), and allyl bromide (17.63 mL, 204 mmol) in acetone (250 mL) was stirred at 70? C. for 18 hours. After cooling to ambient temperature, the suspension was filtered through a pad of Celite and washed with acetone. The filtrate was evaporated, and the crude product (IIICa) was purified by layer crystallization in acetone: pentane. The final product was a yellow powder (Isolated yield: 82%).

[0278] .sup.1H NMR (400 MHz, CDCl.sub.3) ?: 6.79 (d, J=8.3 Hz, 3H, ArH), 6.66 (d, J=2.1 Hz, 3H, ArH), 6.56 (dd, J=8.3, 2.1 Hz, 3H, ArH), 6.08 (ddt, J=17.3, 10.7, 5.4 Hz, 3H), 5.39 (dt, J=17.1, 1.5 Hz, 4H, Ar.sub.3CH, CH.sub.2), 5.26 (dq, J=10.5, 1.4 Hz, 3H, CH), 4.58 (dt, J=5.5, 1.5 Hz, 6H, CH.sub.2), 3.75 (s, 9H, CH.sub.3).

[0279] .sup.13C NMR (101 MHz, CDCl.sub.3) ?: 149.18, ArC, 146.47, ArC, 137.33, ArC, 133.53, ArC, 121.34, CH, 117.95, CH.sub.2, 113.12, ArC, 113.00, ArC, 77.16, 69.92, CH.sub.2, 55.93, CH.sub.3, 55.51, Ar.sub.3C.

[0280] ESI-MS (m/z) calculated for C.sub.31H.sub.34O.sub.6: 502.2349, found: 502.2345.

Steps b) and c) Thiol-ene Reaction Followed by Hydrolysis

[0281] ##STR00031##

[0282] In a first step, tris (4-(allyloxy)-3-methoxyphenyl) methane (20.1 g, 40 mmol) was reacted with thioacetic acid (20 ml, 180 mmol) and AIBN (1.55 mg, 9.6 mmol) by stirring the mixture at 80? C. for 24 hours. The conversion can be monitored by .sup.1H NMR. Subsequently, unreacted thioacetic acid was removed under reduced pressure. The compound was extracted with DCM: 3?H.sub.2O. The organic phase was separated and dried over MgSO.sub.4. Volatiles were removed to obtain the intermediate thioester product.

[0283] For the second step, the compound was dissolved in 100 ml of dry THF and 1.1 equiv. of concentrated HCl (12.9 g) in 40 ml of dry MeOH was added to the solution. The mixture was degassed for 10 minutes under Ar and the solution was stirred at 60? C. for 14 hours. Finally, the solvent was removed and the trithiol was extracted with DCM: 3?H.sub.2O. The organic phase was separated and dried over MgSO.sub.4. Volatiles were removed to obtain the final product. Further purification was done doing vacuum distillation at 120? C. with 5?10.sup.?2 mbar. The final product was a condensed orange liquid (Isolated yield: 85%).

[0284] .sup.1H NMR (300 MHz, CDCl.sub.3) ?: 6.83-6.74 (m, 3H, ArH), 6.66 (d, J=2.1 Hz, 3H, ArH), 6.62-6.52 (m, 3H, ArH), 5.35 (d, J=2.8 Hz, 1H, Ar.sub.3CH), 4.08 (t, J=6.1 Hz, 6H, CH.sub.2), 3.73 (s, 9H, CH.sub.3), 2.71 (dt, J=8.2, 6.9 Hz, 6H, CH.sub.2), 2.17-1.99 (m, 6H, CH.sub.2), 1.42 (t, J=8.1 Hz, 3H, SH).

[0285] .sup.13C NMR (75 MHz, CDCl.sub.3) ?: 149.20, ArC, 146.66, ArC, 137.29, ArC, 121.36, ArC, 113.25, ArC, 113.04, ArC, 77.16, 66.34, CH.sub.2, 55.89, CH.sub.3, 55.41, Ar.sub.3CH, 33.31, CH.sub.2, 21.29, CH.sub.2.

[0286] ESI-MS (m/z) calculated for C.sub.31H.sub.40O.sub.6S.sub.3: 627.1884, found: 627.1888.

[0287] In view of the foregoing description and example, it will be apparent to those skilled in the art that equivalent modifications thereof can be made without departing from the scope of the claims.