Synthesis Of Benzo Heterocycle Photoinitiators

UV curing technology is one of green technology. Because of its green features, it is accepted gradually and developed rapidly. This technology is used in coatings, inks, electronics, biotechnology and other areas widely. UV curing system is mainly made up of UV initiator, resin, monomer and auxiliary. UV curing technology UV initiator is an important part in UV curing system and is crucial to the system, so it is of great concern for many researchers. This paper studied from free-radical photoinitiator and cationic cured photoinitiator. Based on consulting, analyzing, summarizing on relevant literatures, this paper study two of the UV initiator:free radical initiator and cationic photoinitiator, and has done the following three aspects.1. Nucleophilic reactions between nucleophilic reagent containing N-H, S-H bonds, aryl chlorides and bromo ketones were carried out. Nine ketones were synthesized through the reaction. Friedel-Crafts acylations between carbazole, dibenzothiophene heterocycles and benzoyl chloride were carried out. Two ketones were synthesized through the reaction. Ketones containing N, S, as free radical, could enhance the reactivity. Target products were characterized by 1H NMR and 13C NMR etc. The optimal synthesis condition of part products is selected. The optimal reaction condition of 1-(2-ylthio-5-methoxy benzimidazole)-4-methylph-enylketone(7c) is:n(5-methoxye-2-mercaplobenzinidazole):n(p-toluoyl chloride)=1:1.2, under Et3N conditions, reacting for 14h at 60℃ in THF as solvent. The optimal reaction condition of 4,4’-dithio-l-(4-methyiphen-yl)ketone(7e) is:n(4,4r-Thiobisbenzenethiol):n(p-toluoyl chloride)=1:1.2, under pyridine conditions, reacting for 16h at 60℃ in THF as solvent. By UV curing test, all target products were screened out. In addition, products, 1-phenyl-2-dodecanoic sulfonium ethyl ketone(3a) and 4,4’-dithio-l-(4-methylphenyl)ketone(7e), had better reactivity in the UV-curing system. The cured films of 3a and 7e had good hardness and adhesion.2. Series of aryl sulfonium salts were synthesized by dibenzothi-ophene, 1-methyl-2-phenyl-3-phenylsulfideindole and diaryl iodonium trifluoromethanesulfonates. They had higher conjugation degree. Th-e conjugation degree of aryl sulfonium salts was enhanced to make UV-wavelength red shift, so it could improve UV-vis absorption and utilization ratio of aryl sulfonium salts. Products were charact-erized by 1H NMR,13C NMR and MS etc. The better reaction con-ditions of products were optimized. The optimal reaction condition of phenyl dibenzothiophene sulfur trifluoromethanesulfonic salt(12a) is:n(dibenzot-hiophene):n(diaryl triflate)=1:1.2, n[catalyst of Cu(OAc)2]=10mol%, reacting for 3h at 130℃ in solvent-free condition. The optimal reaction condition of diphenyl-(1-methyl-2-phenylindole) sulfur trifluoromethane-sulfonic salt(14a) is:n(the catalyst of Cul and Cu)=10mol%, n(CuI):n(Cu)=1:1, reacting for 3h at 130℃in Cl2CH2CH2Cl2 as solvent. Comparing with 184 by the properties of UV and UV-curing properties, these products were used as cationic pho-toinitiator in UV curing system. The cured film hardness of diphe-nyl-(1-methyl-2-phenyl-indole) sulfur trifluoromethanesulfonicsalts(14a) and Phenyl-(4-methylbenzene)-(1-me-hyl-2-phenylindole)sulfur-trfluoromethanesulfonic salt(14b) was 5H and and better than 184. They could be used in conjunction with 184. In addition, the possible reaction mechanism of 14a has been discussed.3. Two different products of aryl sulfonium salts were synthesized by oxazole ether containing two S and diaryl iodonium trifluoromethanesulf-onate. They had higher conjugation degree. Products were characterized by 1H NMR and 13C NMR etc. The better reaction conditions of products were optimized:n(the catalyst of Cul and Cu)= 10mol%, n(CuI):n(Cu)= 1:1, reacting for 2h at 115℃ in C12CH2CH2C12 as solvent. By Photo-Curing testing, the product could be used in UV curing system as cationic photoinitiator. Phenyl-(2-benzoxazole)-[4-2-ylthio-benzimidazo- le)phenyl]sulphur trifluoromethanesulfonic acid(16a-1) and 4-methylph-enyl-(2-benzoxazole)-[4-2-ylthiobenzimidazole)phenyl]sulphurtrifluorom ethanesulfonic acid(16b-1) had better reactivity. Adhesion of them was better than diaryl iodonium salt.