Exploratory study on photoinduced single electron transfer reactions of .alpha.,.beta.-epoxy ketones with amines
摘要:
Photoinduced single electron transfer (SET) reactions of alpha,-beta-epoxy ketones have been studied using alkylamine electron donors. Irradiation of chalcone epoxide 1 with triethylamine (TEA) afforded beta-diketone 2 and beta-hydroxy ketone 3. Photoreaction of 1 with TEA in MeOH resulted in a slightly increased product ratio (3/2) compared with that in MeCN. When 1,4-diazabicyclo[2.2.2]octane (DABCO) was used instead of TEA, a decrease in the yield of 3 was observed. Only 2 was obtained on irradiation of a solution of 1 in TEA and MeCN containing LiClO4. Studies of photoreactions of dypnone epoxide 9, benzoylisopropylethylene epoxide 12, and acrylophenone epoxide 15 indicate that the nature of beta-substituent also influences the product distribution. It was also found that 1,6-bis(dimethylamino)pyrene (BDMAP) sensitizes the photoreaction of 1 in the presence of TEA to produce 2. Based on the results obtained, a reaction mechanism involving selective C-alpha-O bond cleavage of intermediate alpha,-beta-epoxy ketone anion radicals is proposed.
Exploratory study on photoinduced single electron transfer reactions of .alpha.,.beta.-epoxy ketones with amines
摘要:
Photoinduced single electron transfer (SET) reactions of alpha,-beta-epoxy ketones have been studied using alkylamine electron donors. Irradiation of chalcone epoxide 1 with triethylamine (TEA) afforded beta-diketone 2 and beta-hydroxy ketone 3. Photoreaction of 1 with TEA in MeOH resulted in a slightly increased product ratio (3/2) compared with that in MeCN. When 1,4-diazabicyclo[2.2.2]octane (DABCO) was used instead of TEA, a decrease in the yield of 3 was observed. Only 2 was obtained on irradiation of a solution of 1 in TEA and MeCN containing LiClO4. Studies of photoreactions of dypnone epoxide 9, benzoylisopropylethylene epoxide 12, and acrylophenone epoxide 15 indicate that the nature of beta-substituent also influences the product distribution. It was also found that 1,6-bis(dimethylamino)pyrene (BDMAP) sensitizes the photoreaction of 1 in the presence of TEA to produce 2. Based on the results obtained, a reaction mechanism involving selective C-alpha-O bond cleavage of intermediate alpha,-beta-epoxy ketone anion radicals is proposed.