Study On Riboflavin Derivatives In B-V Reaction And Visible Photocatalytic C-H Oxidation

Oxidation is one of the most fundamental reactions in organic synthesis.Owing to the current need to develop a technology that is environmentally benign with respect to efficient,highly selective formation of products,many aspects must be considered in the search for new catalytic oxidation reactions.Oxidoreductases appear set to become practical catalysts for organic synthesis.Monooxygenases are promising catalysts because they in principle enable the organic chemist to perform highly selective oxyfunctionalisation reactions that are otherwise difficult to achieve.For this,monooxygenases require reducing equivalents,to allow reductive activation of molecular oxygen at the enzymes'active sites.Simulation of the functions of enzymes such as flavoenzymes using simple organocatalysts and transition metal catalysts may lead to the discovery of biomimetic and catalytic oxidation reactions.Flavin-catalysed oxidation is one of the attractive approaches for designing environmentally benign catalytic oxidation reactions with organocatalysts.Using simple riboflavin related compounds as biomimetic catalysts,catalytic oxidation of various substrates with hydrogen peroxide or molecular oxygen can be performed selectively under mild conditions.Inspired by this,this paper mainly studied the aerobic catalyzed Baeyer-Villiger oxidation and the aerobic photocatalytic C-H bond oxidation by riboflavin tetraacetate?RFT?,and successfully immobilized the photocatalyst RFT,simplifies the catalyst recovery process.We researched that biomimetic RFT-catalysed Baeyer-Villiger oxidation with dioxygen was achieved by selecting zinc as the reductant.The conditions of the reaction were optimized according to single factor experiments.The optimal conditions were:cyclopentanone 4 mmol,zinc powder 8 mmol,RFT 0.4 mmol,reaction temperature 60°C,reaction time 6 h,the yield of 1,5-valerolactone was 21%.A green and highly efficient cooperative photocatalytic system which consists of RFT,N-Hydroxysuccinimide?NHS?and FeCl₃·6H₂O has been developed for C-H bond oxygenation with visible light under mild reaction conditions.Compared to the previous procedures about C-H bond activation by using flavins as photocatalyst,we use cheap ferric chloride and NHS instead of expensive scandium triflate or biomimetic non-heme iron complex,further expand the substrate scopes.In addition,a possible radical mechanism for the C-H bond oxygenation in this photocatalytic system is proposed.