Asymmetric Photochemical Synthesis Of The Norrish Type Ⅱ Reaction

Norrish typeⅡphotochemical reaction refers to the carbonyl compounds withγ-H,which is excited to extract theγ-H under UV irradiation, then theβbond is splited, whichgenerates the Olefinic alcohol or the keto olefin. On the other hand, it might generateintramolecular coupled cyclobutanol derivatives. Norrish typeⅡphotochemical reactionis a significant cyclization route which has great applications in organic synthesis. With adetailed study, it was found that in the presence of a large conjugated system, the singleelectron transfer reaction will be accompanied by Norrish typeⅡphotochemical reactionto generate rearrangement product.The first part, in this thesis, we investigated the NorrishⅡphotochemical reactionof the 3-acetyl-4-[benzo-1,3-dimethyl-5-benzyloxy]-methyl benzoate. We assumed thatthe reaction would generate the intermediate lignin of eupomatenoid-X. Eupomatenoid-Xis one of the most important natural compounds, which has excellent anti-fungal activityof the skin, and especially good activity of killing the Trichophyton rubrum. During ourexperiments, we found that photochemical reactions generated different products if weused different kinds of solvents, in the case of acetonitrile, single electron transferoccurred which resulted the compound of 3-acetyl-4-hydroxybenzoate. In other case ofbenzene, we found that a new class of rearrangement phenomenon happened. This typeof rearrangement has not been reported in previous literatures. We tentatively proposedthe reaction mechanism. When the NorrishⅡphotochemical reaction occurs, due to theconjugation of benzene ring, a single electron transfer reaction occurred to produce thealcohol, then, subsequently being oxidized by oxygen into ketone.The second part, we succesfully synthesized 1,2 epoxy-[2.2.1]heptane Ring-7-phenyl ketone through photochemical reaction starting from Norbornene, however, theoptimized experimental conditions remained to be further explored. At the same time, weattempted to synthesize the 3-acetyl-4- [benzo-1,3-dimethyl-5-benzyloxy]-5-methoxy-methyl benzoate. There are also some problems wehave not solve, such as Fries rearrangement or cyclopropanation reactions, which isuseful for further synthetic study.