Silicone-compatible compounds

Abstract

Certain phosphonate compounds useful as photoinitiators are provided herein.

Claims

1. A photoinitiator of the general Formula I: ##STR00032## wherein: R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are the same or different and are selected from the group consisting of SIL.sub.1-X, hydrogen, C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, phenyl C.sub.1-C.sub.3 alkyl, and fluorine; X is optional, and if present is C.sub.1-C.sub.12 alkyl; SIL.sub.1 has the general formula:
(R.sup.7SiO.sub.3/2).sub.a(R.sup.7.sub.2SiO.sub.2/2).sub.b(R.sup.7.sub.3SiO.sub.1/2).sub.c wherein: R.sup.7 is selected from the group consisting of C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, alkoxyl, phenyl, and phenyl C.sub.1-C.sub.3 alkyl; a is a positive number, b is 0 or a positive number, c is 0 or a positive number, b/a is from 0 to 100, and c/a is from 0 to 10, wherein at least one of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 is SIL.sub.1-X; and R.sup.6 is selected from the group consisting of C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, phenyl, phenyl C.sub.1-C.sub.3 alkyl, trimethylphenol, and fluorine, wherein R.sub.3 is SIL.sub.1-X and the SIL.sub.1-X is selected from the group consisting of: ##STR00033##

2. The photoinitiator according to claim 1, wherein R.sup.1 and R.sup.5 are methyl groups and R.sup.2 and R.sup.4 are hydrogen.

3. A photoinitiator of the general Formula I: ##STR00034## wherein: R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are the same or different and are selected from the group consisting of SIL.sub.1-X, hydrogen, C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, phenyl C.sub.1-C.sub.3 alkyl, and fluorine; X is optional, and if present is C.sub.1-C.sub.12 alkyl; SIL.sub.1 has the general formula:
(R.sup.7SiO.sub.3/2).sub.a(R.sup.7.sub.2SiO.sub.2/2).sub.b(R.sup.7.sub.3SiO.sub.1/2).sub.c wherein: R.sup.7 is selected from the group consisting of C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, alkoxyl, phenyl, and phenyl C.sub.1-C.sub.3 alkyl; a is a positive number, b is 0 or a positive number, c is 0 or a positive number, b/a is from 0 to 100, and c/a is from 0 to 10, wherein at least one of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 is SIL.sub.1-X; and R.sub.6 is selected from the group consisting of a phenyl group, CH.sub.3CH.sub.2O, and a trimethylphenol group.

4. The photoinitiator according to claim 1, wherein R.sub.6 is selected from the group consisting of a phenyl group, CH.sub.3CH.sub.2O, and a trimethylphenol group.

5. The photoinitiator according to claim 2, wherein R.sub.6 is selected from the group consisting of a phenyl group, CH.sub.3CH.sub.2O, and a trimethylphenol group.

6. A compound selected from the group consisting of: ##STR00035## ##STR00036## and combinations thereof.

7. A method of synthesizing a compound of the general Formula I: ##STR00037## wherein: R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are the same or different and are selected from the group consisting of SIL.sub.1-X, hydrogen, C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, phenyl C.sub.1-C.sub.3 alkyl, and fluorine; X is optional, and if present is C.sub.1-C.sub.12 alkyl; SIL.sub.1 has the general formula:
(R.sup.7SiO.sub.3/2).sub.a(R.sup.7.sub.2SiO.sub.2/2).sub.b(R.sup.7.sub.3SiO.sub.1/2).sub.c wherein: R.sup.7 is selected from the group consisting of C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, alkoxyl, and phenyl C.sub.1-C.sub.3 alkyl; a is a positive number, b is 0 or a positive number, c is 0 or a positive number, b/a is from 0 to 100, and c/a is from 0 to 10, wherein at least one of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 is SIL.sub.1-X; and R.sup.6 is selected from the group consisting of C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, phenyl, phenyl C.sub.1-C.sub.3 alkyl, trimethylphenol, and fluorine, comprising the steps of: 1) Activating a compound of Formula A: ##STR00038## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are as above, but none may be SIL.sub.1-X, to produce a compound of Formula B: ##STR00039## 2) Subjecting the compound of Formula B to a nucleophilic acetate substitution reaction to produce a compound of Formula C: ##STR00040## 3) Subjecting the compound of Formula C to a hydrolysis reaction to produce a compound of Formula D: ##STR00041## and 4) Subjecting the compound of Formula D to a condensation reaction with a compound having the formula SIL.sub.1-XCl or SIL.sub.1-XH to produce the compound of Formula 1.

8. A composition comprising: a) about 70 to about 99.9 weight percent of a photocurable silicone; and b) about 0.1 to about 10.0 weight percent of a compound of the general Formula I: ##STR00042## wherein: R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are the same or different and are selected from the group consisting of SIL.sub.1-X, hydrogen, C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, phenyl C.sub.1-C.sub.3 alkyl, and fluorine; X is optional, and if present is C.sub.1-C.sub.12 alkyl; SIL.sub.1 has the general formula:
(R.sup.7SiO.sub.3/2).sub.a(R.sup.7.sub.2SiO.sub.2/2).sub.b(R.sup.7.sub.3SiO.sub.1/2).sub.c wherein: R.sup.7 is selected from the group consisting of C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, alkoxyl, phenyl, and phenyl C.sub.1-C.sub.3 alkyl; a is a positive number, b is 0 or a positive number, c is 0 or a positive number, b/a is from 0 to 100, and c/a is from 0 to 10, wherein at least one of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 is SIL.sub.1-X; and R.sup.6 is selected from the group consisting of C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, phenyl, phenyl C.sub.1-C.sub.3 alkyl, trimethylphenol, and fluorine.

9. The composition according to claim 8, wherein R.sub.3 is SIL.sub.1-X and the SIL.sub.1-X is selected from the group consisting of: ##STR00043##

10. The composition according to claim 9, wherein R.sup.1 and R.sup.5 are methyl groups and R.sup.2 and R.sup.4 are hydrogen.

11. The composition according to claim 8, wherein R.sub.6 is selected from the group consisting of a phenyl group, CH.sub.3CH.sub.2O, and a trimethylphenol group.

12. The composition according to claim 9, wherein R.sub.6 is selected from the group consisting of a phenyl group, CH.sub.3CH.sub.2O, and a trimethylphenol group.

13. The composition according to claim 10, wherein R.sub.6 is selected from the group consisting of a phenyl group, CH.sub.3CH.sub.2O, and a trimethylphenol group.

14. The composition according to claim 8, wherein the compound of the general Formula I is selected from the group consisting of: ##STR00044## ##STR00045## and combinations thereof.

15. The composition according to claim 8, wherein the photocurable silicone is a UV curable organosilicone or a UV and moisture dual cure silicone.

16. The composition according to claim 8, wherein the photocuable silicone is a (meth)acrylic endcapped silicone.

17. The composition according to claim 8, wherein the photocuable silicone is a (meth)acrylic endcapped silanol terminated polydimethylsiloxane.

18. A method of making a silicone polymer product, comprising the steps of: A) Providing a photocurable silicone composition comprising: i) about 70 to about 99.9 weight percent of a photocurable silicone; and ii) about 0.1 to about 10.0 weight percent of a compound of the general Formula I: ##STR00046## wherein: R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are the same or different and are selected from the group consisting of SIL.sub.1-X, hydrogen, C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, phenyl C.sub.1-C.sub.3 alkyl, and fluorine; X is optional, and if present is C.sub.1-C.sub.12 alkyl; SIL.sub.1 has the general formula:
(R.sup.7SiO.sub.3/2).sub.a(R.sup.7.sub.2SiO.sub.2/2).sub.b(R.sup.7.sub.3SiO.sub.1/2).sub.c wherein: R.sup.7 is selected from the group consisting of C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, alkoxyl, phenyl, and phenyl C.sub.1-C.sub.3 alkyl; a is a positive number, b is 0 or a positive number, c is 0 or a positive number, b/a is from 0 to 100, and c/a is from 0 to 10, wherein at least one of R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 is SIL.sub.1-X; and R.sup.6 is selected from the group consisting of C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, phenyl, phenyl C.sub.1-C.sub.3 alkyl, trimethylphenol, and fluorine; and B) Exposing the photocurable silicone composition to ultraviolet radiation or visible light to initiate photocuring of the photocurable silicone composition to produce the silicone polymer product.

19. The method according to claim 18, wherein the photocurable silicone is a UV curable organosilicone or a UV and moisture dual cure silicone.

20. The method according to claim 18, wherein the photocurable silicone is a (meth)acrylic endcapped silicone.

21. The method according to claim 18, wherein the photocurable silicone is a (meth)acrylic endcapped silanol terminated polydimethylsiloxane.

22. The method according to claim 18, wherein the ultraviolet radiation has a wavelength of about 390 nanometers or greater.

23. The method according to claim 18, wherein the ultraviolet radiation has a wavelength of about 405 nanometers.

24. The method of making a silicone polymer product of claim 18, further comprising the step of placing the photocurable silicone composition in contact with at least one layer of an optically clear composition prior to the initiation of photocuring, wherein when the photocurable silicone composition is cured the silicone polymer product is suitable for use in an optically clear display.

25. The method of making a silicone polymer product of claim 24, wherein the optically clear composition is glass.

26. The method of making a silicone polymer product of claim 24, further comprising the step of placing the photocurable silicone composition between two layers of an optically clear composition prior to the initiation of photocuring, wherein when the photocurable silicone composition is cured the silicone polymer product is suitable for use in an optically clear display.

27. The method of making a silicone polymer product of claim 26, wherein the optically clear composition is glass.

28. The method of making a silicone polymer product of claim 26, wherein the silicone polymer product has a haze value of about 1 or less and a yellowness value of about 1 or less at a gap of 750 micrometers between the two layers of the optically clear composition when aged for 500 hours in a QUV test machine or when aged for 500 hours in an oven at 85 C. and 85% relative humidity.

Description

DETAILED DESCRIPTION

(1) The compounds according to the invention may be used as photoinitiators and are particularly effective if used in compositions based on photocurable silicones.

(2) The SIL.sub.1-X group in the compound of the present invention is represented by the formula:
(R.sup.7SiO.sub.3/2).sub.a(R.sup.7.sub.2SiO.sub.2/2).sub.b(R.sup.7.sub.3SiO.sub.1/2).sub.c
wherein R.sup.7 is a C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.8 alkenyl, C.sub.5-C.sub.8 cycloalkyl, alkoxyl, phenyl, or phenyl C.sub.1-C.sub.3 alkyl group. Moreover, a is a positive number, b is 0 or a positive number, c is 0 or a positive number, b/a is from 0 to 100, and c/a is from 0 to 10. X is optional, and if present is a C.sub.1-C.sub.12 alkyl group.

(3) Preferably, X is not present, R.sup.7 is a methyl group or a methoxy group, a is 1, b is 0, and c is 2 or 3.

(4) The compounds of the present invention may contain up to 5 SIL.sub.1-X groups, one each at R.sub.1 through R.sub.5. Preferably, the compounds of the present invention contain 1, 2, or 3 SIL.sub.1-X groups at one or more of R.sup.1, R.sup.2, or R.sup.3. In one embodiment, compounds of the present invention contain a single SIL.sub.1-X group at R.sup.3. Preferably, if not occupied by a SIL.sup.1-X group, R.sup.1 and R.sup.5 are methyl groups and R.sup.2 and R.sup.4 are hydrogen.

(5) The compounds according to the invention show advantageous properties if R.sub.3 is SIL.sub.1-X and the SIL.sub.1-X is:

(6) ##STR00009##
R.sup.1 and R.sup.5 are methyl groups, and R.sup.2 and R.sup.4 are hydrogen.

(7) R.sup.6 is a C.sub.1-C.sub.20 alkyl group, a C.sub.2-C.sub.8 alkenyl group, a C.sub.5-C.sub.8 cycloalkyl group, a phenyl group, a phenyl C.sub.1-C.sub.3 alkyl group, a trimethylphenol group, or fluorine. Preferably, R.sup.6 is a phenyl group, CH.sub.3CH.sub.2O, or a trimethylphenol group.

(8) The compounds according to the invention show particularly advantageous properties if R.sub.3 is SIL.sub.1-X and the SIL.sub.1-X is:

(9) ##STR00010##
R.sup.1 and R.sup.5 are methyl groups, R.sup.2 and R.sup.4 are hydrogen, and R.sub.6 is a phenyl group, CH.sub.3CH.sub.2O, or a trimethylphenol group.

(10) Preferably, the compound of the present invention is one of the following:

(11) ##STR00011## ##STR00012##
These compounds may be employed alone or in combination in the compositions and methods of the present invention.

(12) The compounds of the present invention may be synthesized through a customizable four-step process to allow for diversity in the possible silicone-compatible photoinitiators that may be produced. The four steps of the synthesis may generally described as follows:

(13) Step 1) The phenyl group of the -hydroxy-alkylphenone starting material is activated by addition of a bromine to the phenyl group though electrophilic halogenation;

(14) Step 2) The bromine is then substituted with acetate by a nucleophilic acetate substitution reaction;

(15) Step 3) The acetate is then hydrolyzed to a hydroxy group through a hydrolysis reaction; and

(16) Step 4) The silicone side chain is then attached to the phenyl group of the -hydroxy-alkylphenone through a condensation reaction to produce the compound of the invention.

(17) The reaction scheme for synthesis of the compounds of the present invention may be generally represented as follows:

(18) ##STR00013##

(19) The preferred general parameters for the synthesis of the compounds of the present invention are shown in Table 1.

(20) TABLE-US-00001 TABLE 1 More Preferred Preferred Step Parameter Range Range Step 1 Ratio of starting 0.1-100 0.8-1.2 Bromized material to N- Reaction bromosuccinimide (NBS) Temperature 20-200 C. 50-150 C. Step 2 Ratio of Compound 0.1-100 0.8-1.2 Nucleophilic of Formula B to Substitution silver Reaction acetate(AgOAc) Temperature 20-220 C. 50-150 C. Step 3 Molar ratio of 0.1-100 0.8-1.2 Hydrolysis acetate to water Reaction Temperature 20-220 C. 50-150 C. Step 4 Molar ratio of 0.1-100 0.8-1.2 Condensation hydroxyl ketone to Reaction CH.sub.3- or Cl-silicone side chain Temperature 20-220 C. 50-150 C.

(21) Desirably, starting materials for the synthesis of the compounds of the present invention are -hydroxy-alkylphenones, examples of which may be represented by the compound of Formula A:

(22) ##STR00014##
in which R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are the same as in the compounds of the present invention (as described above), but none may be SIL.sub.1-X, and R.sup.6 is the same as in the compounds of the present invention.

(23) Preferably, R.sup.1, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 are independently hydrogen or methyl groups. In preferred starting materials R.sup.1, R.sup.3, and R.sup.5 are methyl groups and R.sup.2 and R.sup.4 are hydrogen. Preferably, R.sub.6 is a phenyl group, CH.sub.3CH.sub.2O, or a trimethylphenol group in the starting material.

(24) Preferred starting materials include the following compounds:

(25) ##STR00015##

(26) A further aspect of the invention is the use of these compounds as photoinitiators. A particular aspect of the invention is a method of using the compounds according to the invention as photoinitiators including the steps of mixing the compound with a photocurable silicone, such as a photopolymerizable organopolysiloxane or silicone resin, and exposing the resulting mixture to electromagnetic radiation.

(27) Although there is no particular limitation regarding the photocurable silicone, it is preferred to add the compound according to the invention to a composition based solely or predominately on (meth)acryloxysiloxanes, e.g., (meth)acrylic endcapped silanol terminated polydimethylsiloxane, since photocuring such mixtures results in products having a degree of haze of less than about 2, preferably less than about 1, a degree of yellowing of less than about 2, preferably less than about 1, and showing very good thermal, hydrolytic, and UV stability. Preferably, the photocurable silicone is an organopolysiloxane or silicone resin, a (meth)acrylic endcapped silicone, a (meth)acryloxysiloxane, or a (meth)acrylic endcapped silanol terminated polydimethylsiloxane.

(28) Useful electromagnetic radiation is any radiation that will provoke forming of radicals and, hence, start free-radical polymerization of the photocurable silicone. An example of such electromagnetic radiation is UVV radiation (ultraviolet light at wavelengths of about 390 nanometers or greater).

(29) A further aspect of the invention is a composition comprising: a) at least one photocurable silicone and b) a compound according to the invention. Preferably, the photocurable silicone is an organopolysiloxane or silicone resin, a (meth)acrylic endcapped silicone, a (meth)acryloxysiloxane, or a (meth)acrylic endcapped silanol terminated polydimethylsiloxane. Preferred photocurable silicones include ultraviolet curable organosilicones and ultraviolet and moisture dual cure silicones.

(30) The amount of the compound according to the invention in such compositions may vary within broad limits. Preferably, the composition of the invention comprises the compound according to the invention or a mixture of several compounds according to the invention in a total amount of 0.1 to 30% by weight, preferably 0.2 to 15% by weight, more preferably 0.5 to 10% by weight, based on the weight of the composition. The remainder generally consists solely or predominantly of the photocurable silicone.

(31) Yet another aspect of the invention is method of making a silicone polymer product by exposing a composition including a) at least one photocurable silicone and b) a compound according to the invention to electromagnetic radiation to initiate photocuring to produce the silicone polymer product. Preferably, the electromagnetic radiation is UVV radiation (ultraviolet light at wavelengths of about 390 nanometers or greater), more preferably ultraviolet radiation at a wavelength of about 405 nanometers.

(32) In preferred embodiments, the method of making a silicone polymer product includes the further step of placing the photocurable silicone composition in contact with at least one layer of an optically clear composition prior to the initiation of photocuring. Thus, when the photocurable silicone composition is cured, the silicone polymer product is suitable for use in an optically clear display. Preferably, the method of making a silicone polymer product of the invention includes the step of placing the photocurable silicone composition between two layers of an optically clear composition prior to the initiation of photocuring.

(33) Optically clear compositions for use in the methods of the invention include any material which provides a transmittance of visible light of greater than about 95%, preferably greater than about 98%, even more preferably greater than about 99%. Preferably, the optically clear composition is glass.

(34) Preferably, the polymer products of the invention exhibit excellent clarity and maintain such clarity even in the face of long periods of aging. Preferably, the silicone polymer products of the invention have a haze value of about 2 or less, more preferably about 1 or less, and a yellowness value of about 2 or less, more preferably about 1 or less, at a gap of 750 micrometers between layers of optically clear composition, when aged for 500 hours in a QUV test machine or when aged for 500 hours in an oven at 85 C. and 85% relative humidity. Preferably, the silicone polymer products of the invention provide a transmittance of visible light of greater than about 95%, preferably greater than about 98%, even more preferably greater than about 99%.

(35) Below is a description of particular aspects of the present invention using a series of examples, however, the present invention is in no way restricted to the below presented examples.

EXAMPLES

Synthesis Example 1

(36) Step 1:

(37) ##STR00016##

(38) A mixture of Darocur TPO (17.5 g, 50.3 mmol), N-bromosuccinimide (12.5 g, 70.4 mmol), AIBN (201 mg), and tetrachloromethane (100 ml) was charged into a 250 ml three-necked flask and refluxed at 80 C. for 5 hours under argon. The reaction mixture was filtered after cooling. The filtrate was evaporated to obtain a crude product.

(39) Step 2:

(40) ##STR00017##

(41) A mixture of the crude product of STEP 1 (without further purification), silver acetate (10.07 g, 60.35 mmol), and 150 ml glacial acetic acid was charged into a 500 ml three-necked flask and refluxed at 100 C. for 3 hours under argon. The mixture was filtered and 500 ml of water was added to the filtrate. The resulting mixture was extracted with CH.sub.2Cl.sub.2 (50 ml) 3 times. The combined organic layer was washed with 50 ml of water, dried over anhydrous Na.sub.2SO.sub.4, and the solvent removed under reduced pressure. The crude product was purified by column chromatography (50% EtOAc in hexane) to produce 7.4 g of intermediate compound (36% yield for combined STEPS 1 and 2).

(42) Step 3:

(43) ##STR00018##

(44) A mixture of the purified intermediate of STEP 2 (7.4 g, 18.2 mmol), THF (44 ml), HCl (10.5 ml), and water (52 ml) was charged into a 250 ml three-necked flask and refluxed at 80 C. overnight under argon. The THF was removed under reduced pressure and 15 ml of water was added. The resulting mixture was extracted with CH.sub.2Cl.sub.2 (30 ml) 3 times. The combined organic layer was washed with 10 ml of water. The organic layer was then dried over anhydrous Na.sub.2SO.sub.4, and the solvent was evaporated. This crude product (9.1 g, yellow solid) was used in the next step without further purification.

(45) Step 4:

(46) ##STR00019##

(47) A solution of the crude product of STEP 3 (9 g, 24.7 mmol), imidazole (3.36 g, 49.4 mmol), and DMAP (40 mg) in CH.sub.2Cl.sub.2 (100 ml) was charged into a 250 ml three-necked flask and ClSi(CH.sub.3SiO).sub.3 (9.82 g, 29.63 mmol) was added. The mixture was stirred at room temperature overnight under argon. The reaction was quenched by addition of water. The aqueous phase was extracted with CH.sub.2Cl.sub.2 (20 ml) 3 times. The combined organic phase was washed with water and brine. The organic phase was dried with anhydrous Mg.sub.2SO.sub.4. After solvent removal under reduced pressure, the residue was purified by column chromatography to produce 10.98 g of the compound of the invention (67% yield, light yellow solid).

Synthesis Example 2

(48) Step 1:

(49) ##STR00020##

(50) A mixture of Compound A2 (above) (12.65 g, 40.0 mmol), N-bromosuccinimide (8.54 g, 48.0 mmol), AIBN (160.0 mg), and tetrachloromethane (80 ml) was charged into a 250 ml three-necked flask and refluxed at 80 C. for 5 hours under argon. The reaction mixture was filtered after cooling. The filtrate was evaporated to obtain a crude product.

(51) Step 2:

(52) ##STR00021##

(53) A mixture of the crude product of STEP 1 (without further purification), silver acetate (8.01 g, 48.0 mmol), and 100 ml glacial acetic acid was charged into a 250 ml three-necked flask and refluxed at 120 C. for 3 hours under argon. The mixture was filtered and 500 ml of water was added to the filtrate. The resulting mixture was extracted with CH.sub.2Cl.sub.2 (50 ml) 3 times. The combined organic layer was washed with 50 ml of water, dried over anhydrous Na.sub.2SO.sub.4, and the solvent removed under reduced pressure. The crude product was purified by column chromatography (50% EtOAc in hexane) to produce 6.18 g of intermediate compound (41% yield for combined STEPS 1 and 2).

(54) Step 3:

(55) ##STR00022##

(56) A mixture of the purified intermediate of STEP 2 (6.18 g, 16.5 mmol), THF (40 ml), HCl (9.5 ml), and water (47 ml) was charged into a 250 ml three-necked flask and refluxed at 80 C. overnight under argon. The THF was removed under reduced pressure and 15 ml of water was added. The resulting mixture was extracted with CH.sub.2Cl.sub.2 (30 ml) 3 times. The combined organic layer was washed with 10 ml of water. The organic layer was then dried over anhydrous Na.sub.2SO.sub.4, and the solvent was evaporated. This crude product (4.8 g, yellow liquid) was used in the next step without further purification.

(57) Step 4:

(58) ##STR00023##

(59) A solution of the crude product of STEP 3, imidazole (2.24 g 33.5 mmol), DMAP (25 mg) in CH.sub.2Cl.sub.2 (60 ml) was charged into a 250 ml three-necked flask and ClSi(CH.sub.3SiO).sub.3 (8.2 g, 27.4 mmol) was added. The mixture was stirred at room temperature overnight under argon. The reaction was quenched by addition of water. The aqueous phase was extracted with CH.sub.2Cl.sub.2 (20 ml) 3 times. The combined organic phase was washed with water and brine. The organic phase was dried with anhydrous Mg.sub.2SO.sub.4. After solvent removal under reduced pressure, the residue was purified by column chromatography (20% EtOAc in hexane) to produce 4.76 g of the compound of the invention (45% yield, light yellow liquid).

Synthesis Example 3

(60) Step 1:

(61) ##STR00024##

(62) A mixture of Compound A2 (above)(12.65 g, 40.0 mmol), N-bromosuccinimide (8.54 g, 48.0 mmol), AIBN (160.0 mg), and tetrachloromethane (80 ml) was charged into a 250 ml three-necked flask and refluxed at 80 C. for 5 hours under argon. The reaction mixture was filtered after cooling. The filtrate was evaporated to obtain a crude product.

(63) Step 2:

(64) ##STR00025##

(65) A mixture of the crude product of STEP 1 (without further purification), silver acetate (8.01 g, 48.0 mmol), and 100 ml glacial acetic acid was charged into a 250 ml three-necked flask and refluxed at 120 C. for 3 hours under argon. The mixture was filtered and 500 ml of water was added to the filtrate. The resulting mixture was extracted with CH.sub.2Cl.sub.2 (50 ml) 3 times. The combined organic layer was washed with 50 ml of water, dried over anhydrous Na.sub.2SO.sub.4, and the solvent removed under reduced pressure. The crude product was purified by column chromatography (50% EtOAc in hexane) to produce 6.18 g of intermediate compound (41% yield for combined STEPS 1 and 2).

(66) Step 3:

(67) ##STR00026##

(68) A mixture of the purified intermediate of STEP 2 (6.18 g, 16.5 mmol), THF (40 ml), HCl (9.5 ml), and water (47 ml) was charged into a 250 ml three-necked flask and refluxed at 80 C. overnight under argon. The THF was removed under reduced pressure and 15 ml of water was added. The resulting mixture was extracted with CH.sub.2Cl.sub.2 (30 ml) 3 times. The combined organic layer was washed with 10 ml of water. The organic layer was then dried over anhydrous Na.sub.2SO.sub.4, and the solvent was evaporated. This crude product (4.8 g, yellow liquid) was used in the next step without further purification.

(69) Step 4:

(70) ##STR00027##

(71) A solution of the crude product of STEP 3 (3.0 g, 9.0 mmol), imidazole (1.36 g, 20.0 mmol), and DMAP (20 mg) in Toluene (40 ml) was charged into a 250 ml three-necked flask and (CH.sub.3SiO).sub.2SiCH.sub.3H (18.0 mmol) was added. The mixture was stirred at room temperature overnight under argon. The reaction was quenched by addition of water (30 ml). The aqueous phase was extracted with CH.sub.2Cl.sub.2 (30 ml) 3 times. The combined organic phase was washed with water and brine. The organic phase was dried with anhydrous Mg.sub.2SO.sub.4. After solvent removal under reduced pressure, the residue was purified by column chromatography (PE:EA=5:1) to produce 3.55 g of the compound of the invention (71% yield, light yellow liquid).

Example 4

(72) Evaluation of Photoinitiators

(73) The compounds of Examples 2 and 3 above and comparative photoinitiators Darocur TPO and SPI-7 were evaluated for applicable cure initiation source, UV resistance, anti-yellowing, and anti-haze properties. Darocur TPO is a photoinitiator that is known for use with UVV radiation for curing. SPI-7 is a silicone substituted UVA photoinitiator. The structure of each of the compounds is shown below.

(74) Compound of Example 2:

(75) ##STR00028##
Compound of Example 3:

(76) ##STR00029##
Darocur TPO:

(77) ##STR00030##
SPI-7:

(78) ##STR00031##

(79) The substrate used was acrylate silicone matrix (15MDMA:60DMA=6.4). The photoinitiators were each separately mixed with the substrate. These mixtures were then placed between 2 layers of glass separated by 750 micrometers and exposed to ultraviolet light. Initiation of curing was evaluated with UV radiation using the medium pressure mercury arch (MPMA) System UV chamber for 30 seconds at 75 mW/cm.sup.2 twice to produce curing. Separately, initiation of curing was also evaluated using a 405 nanometer LED light source.

(80) After curing, the samples were aged in a QUV test machine for 500 hours. After aging, hazing and yellowing for each sample were measured using a Datacolor 650 apparatus, available from Datacolor Corporation, in compliance with ASTM D1003 Standard Test Method.

(81) The light source(s) capable of initiating curing and the results for hazing and yellowing are reported in Table 2.

(82) TABLE-US-00002 TABLE 2 Light Source(s) Capable of Initiating Yellowing Photoinitiator Curing Hazing Value Value (b) Darocur TPO MPMA & 405 nm 7.1 0.98 Example 2 MPMA & 405 nm 0.1 0.60 SPI-7 MPMA 0.1 0.33 Example 3 MPMA & 405 nm 0.2 1.60

(83) Hazing and yellowing values were determined at a gap of 750 micrometers. Hazing and yellowing values of about 2 or less were considered acceptable, and values of about 1 or less were considered excellent.

(84) Based on the results reported in the Table 2, only the compounds of the invention produced acceptable hazing and yellowing values and could initiate curing using 405 nm ultraviolet light. The compound of Example 2 showed excellent values for both hazing and yellowing. Darocur TPO, which is free of silicone side chains, produced unacceptable hazing upon aging, and curing could not be initiated using 405 nm ultraviolet light with SPI-7.