PRODUCTION OF AROMATIC ACIDS AND PHENOLICS

Abstract

The invention is directed to a process for the preparation of an aromatic acid or a phenolic compound, said process comprising reacting a dienophile and a furanic compound comprising an acetal moiety in a Diels-Alders reaction to obtain an aromatic compound comprising said acetal moiety, followed by hydrolysis and oxidation of said acetal moiety into a hydroxide or carboxylate moiety to form the aromatic acid or phenolic compound, wherein said dienophile is selected from the group consisting of alkylenes, acetylenes, acrylates, maleates, fumarates, maleimides, propiolates, acetylene dicarboxylates, and benzynes and wherein said acetal moiety is bound directly to the 2-position of the furanic compound.

Claims

1. Method for the preparation of an aromatic acid or a phenolic compound, said method comprising reacting a dienophile and a furanic compound comprising an acetal moiety in a Diels-Alders reaction to obtain an aromatic compound comprising said acetal moiety, followed by hydrolysis and oxidation of said acetal moiety into a hydroxide or carboxylate moiety to form the aromatic acid or phenolic compound, wherein said dienophile is selected from the group consisting of alkylenes, acetylenes, acrylates, maleates, fumarates, maleimides, propiolates, acetylene dicarboxylates, and benzynes and wherein said acetal moiety is bound directly to the 2-position of the furanic compound.

2. The method according to claim 1, wherein the furanic compound has a structure according to formula I, ##STR00014## wherein, R.sup.1 is selected from the group consisting of H, C.sub.1-C.sub.20 alkyl, CH(OR.sup.2)(OR.sup.3), CH.sub.2OH and esters and ethers thereof, CO.sub.2H and esters thereof, and amides and tertiary amines of CH.sub.2NH.sub.2, and optionally polymer supported; preferably H, methyl or CH.sub.2O(C.sub.1-C.sub.20 alkyl); and R.sup.2 and R.sup.3 are independently a C.sub.1-C.sub.20 hydrocarbyl, preferably C.sub.1-C.sub.12 hydrocarbon, more preferably C.sub.1-C.sub.8 hydrocarbon, even more preferably benzyl or C.sub.1-C.sub.8 alkyl such as methyl, ethyl, propyl, 2-propyl, n-butyl, tert-butyl, pentyl, hexyl or octyl; or wherein R.sup.2 and R.sup.3 together form a ring and represent a C.sub.1-C.sub.20 hydrocarbylene, preferably selected from the group consisting of (CH.sub.2).sub.2, (CH(C.sub.1-C.sub.10 alkyl)CH.sub.2, (CH.sub.2).sub.3, (C(CH.sub.3).sub.2).sub.2, (C(CH.sub.3).sub.2CH.sub.2C(CH.sub.3).sub.2) and 1,2-phenylene.

3. The method according to claim 1, wherein the dienophile has a structure according to formula II, ##STR00015## wherein R.sup.4 and R.sup.5 are each independently selected from the group consisting of H, C.sub.1-C.sub.8 hydrocarbyl such a methyl, ethyl and phenyl, CO.sub.2Z wherein Z is H or an optionally halogenated C.sub.1-C.sub.8 hydrocarbyl such as methyl, ethyl, phenyl, 1,1,1,3,3,3-hexafluoroisopropyl and trifluoroethyl, preferably wherein one of R.sup.4 and R.sup.5 is H, or R.sup.4 and R.sup.5 together form a ring and represent (CO)X(CO), wherein XO, CH.sub.2, NH, NMe, NEt, NPr, NBu, NPh, or S; preferably R.sup.4 and R.sup.5 together form a ring and represent (CO)O(CO), (CO)NMe(CO), (CO)NEt(CO) or (CO)NPr(CO); and wherein represent a double or triple bond, preferably a double bond.

4. The method according to claim 1, wherein the aromatic acid has a structure according to formula IVaa and the phenolic compound has a structure according to formula IVab or esters and ethers thereof; ##STR00016## and wherein compounds I, IIa and IIIa as well as R.sup.1, R.sup.4 and R.sup.5 of formulae IVaa and IVab are defined according to claims 2 and 3.

5. The method according to claim 1, wherein the aromatic acid has a structure according to formula IVba and the phenolic compound has a structure according to formula IVbb or esters and ethers thereof; ##STR00017## and wherein compound I, IIb and IIIb as well as R.sup.1, R.sup.4 and R.sup.5 of formulae IVba and IVbb are defined according to claims 2 and 3.

6. The method according to claim 4, wherein the aromatic acid or the phenolic compound is such that R.sup.1 is selected from the group consisting of H, C.sub.1-C.sub.20 alkyl, CH.sub.2O-alkyl, preferably H, methyl or CH.sub.2O(C.sub.1-C.sub.20 alkyl); and R.sup.4 and R.sup.5 are each independently H or CO.sub.2H.

7. The method according to claim 1, wherein said method further comprises preparing the furanic compound comprising an acetal moiety by reacting a corresponding furfural compound with an alcohol or diol under dehydrating conditions, preferably wherein said alcohol has a structure according to R.sup.2OH and/or R.sup.3OH wherein R.sup.2OH and/or R.sup.3OH are independently a C.sub.1-C.sub.20 hydrocarbyl and said diol is selected from the group consisting of a C.sub.1-C.sub.20 hydrocarbylenediol, preferably selected from the group consisting of HO(CH.sub.2).sub.2OH, HO(CH.sub.2).sub.3OH, HO(CH(C.sub.1-C.sub.10 alkyl)CH.sub.2OH , HO(C(CH.sub.3).sub.2).sub.2OH, HO(C(CH.sub.3).sub.2CH.sub.2C(CH.sub.3).sub.2)OH and catechol.

8. The method according to claim 1, wherein reacting the dienophile with the furanic compound is catalyzed by a Lewis and/or Brnsted acid.

9. The method according to claim 1, wherein the hydrolysis and oxidation are carried out in two separate steps.

10. The method according to claim 1, wherein reacting the dienophile and the furanic compound in a Diels-Alders reaction to obtain the aromatic compound comprises the formation and optionally isolation of an intermediate cycloadduct according to formula V and ring-opening and aromatizing said intermediate to form said aromatic compound, ##STR00018## wherein R.sup.1-R.sup.5 are as defined in claims 2 and 3 and represents a double or single bond, preferably a single bond.

11. The method according to claim 1, wherein said hydrolysis of the aromatic compound results in the formation and optionally isolation of an intermediate aldehyde, which intermediate aldehyde preferably has a structure according to formulae VIa or VIb, ##STR00019## wherein R.sup.1, R.sup.4 and R.sup.5 are as defined in claims 2 and 3.

Description

EXAMPLE 1

[0039] ##STR00011##

[0040] To four stirred tubes charged with maleic anhydride (1 g) and MTBE (1 ml, 2 ml, 3 ml or 4 ml) was added. The mixtures were heated to 40 C. with stirring to achieve a solution, then ethylene glycol acetal of furfural (2-(furan-2-yl)-1,3-dioxolane, 1.461 g, 1.218 ml) was added slowly, preventing an exotherm greater than 50 C. This gave a light yellow/orange solution. This was stirred at 40 C. for 1 hour, then allow to 20 C. and left to stir overnight. After this time all of the mixtures had precipitated. The most concentrated reaction had stopped stirring, and the second most concentrated was stirring with difficulty, so these were broken up. The two least concentrated were stirring well. Each of the solids was then isolated by vacuum filtration (with the exception of the most concentrated as this was totally solidified, and washed with MTBE (5 mlto rinse out the tube and wash the solid). The solids were then dried in a vacuum oven (2 mbar, 20 C.) to yield white solid products (2.277 g, 92%; 1.84 g, 74%; 1.674 g, 68% respectively for most concentrated to least concentrated). The products were combined and then analysed by NMR, which confirmed clean desired product as a mixture of 2 stereoisomers (assumed to be endo- and exo-).

EXAMPLE 2

[0041] To a 50 ml round-bottom flask was charged maleic anhydride (8.143 g), then MTBE (17.0 ml) was added. The mixture was heated to 40 C. with stirring, to achieve a solution, then furfural ethylene glycol acetal (11.90 g, 9.917 ml) was added slowly, preventing an exotherm greater than 50 C. This was stirred at 40 C. for 20 minutes, then allowed to cool to 20 C. The mixture was then seeded with a small amount of product from a previous batch, and a very fine white precipitate quickly formed. The mixture was cooled to 0 C. (ice/water bath) with stirring, and held for a period of 4 hours. Then the formed solids were isolated by vacuum filtration and washed with ice-cold MTBE (10 ml). The isolated solids were dried in a vacuum oven (2 mbar, 20 C.) to yield a white solid (18.53 g, 92%). The structure of the desired product was confirmed as a mixture of 2 regioisomers (assumed to be endo- and exo-) in 1:1 ratio by NMR.

EXAMPLE 3

[0042] ##STR00012##

[0043] A 100 ml autoclave reactor was charged with the Diels-Alder adduct of furfural-ethylene glycol-acetal and maleic anhydride (5 g) and 10% palladium on carbon (1 g), then THF (50 ml) was added. The reactor was quickly sealed and flushed to 15 bar 3 times with nitrogen. Then the reactor was charged to 55 bar of hydrogen. Stirring was started at 1800 rpm. During a quick exotherm to 42 C., the pressure dropped to 40 bar. The pressure was increased again to 55 bar and the mixture was stirred for 18 hours, during which time the mixture cooled to ambient. The mixture was filtered through celite, washing the cake with THF (225 ml). The combined filtrates were evaporated to dryness to yield a white solid (5.00 g, 99%). This was analysed by NMR and confirmed to be clean desired product.

EXAMPLE 4

[0044] ##STR00013##

To a reactor with stirrer was charged furfural-ethylene glycol-acetal (10 g), dimethyl acetylenedicarboxylate (30.36 g) and toluene (80 ml) and the mixture was heated to 100 C. and held for 4 hours. The set-up was then re-configured for distillation and the toluene and excess dimethyl acetylenedicarboxylate were recovered by distillation. The residual liquid (19.78 g, 98%) was analysed by NMR and confirmed to be the desired Diels-Alder adduct product.