Visible-Light-Driven Radical Transformation Of Alcohols Upon β-Scission

Given the ubiquity in natural products and industrial chemicals,the catalytic conversion of alcohols has long been an attractive target in organic chemistry.Traditionally,polar reactions in which the alcohols are used as nucleophiles or electrophiles.In recent years,visible-light-driven radical reactions involving alcohols and their derivatives as radical precursors have become an important method for the construction of C-C bonds or C-X bonds due to the high reactivity and mild conditions.Visible-light-driven alkyl radical reactions represent one of the most attractive.The generation of alkyl radicals from alcohols via the homolytic cleavage of C–C bonds or C-O bonds cleavage has emerged as a powerful strategy for the radical transformation of alcohols,however,the reaction types are plenty of room for improvement.In this dissertation,we present novel visible-light-driven radical reactions using alcohols as alkyl radical precursors,including:The first part:By utilizing a photoredox/cobaloxime dual catalytic system,sequential ring-opening C–C bond scission and dehydrogenation of nonstrained tertiary cycloalkanols of variable ring sizes are achieved under visible light irradiation,producing a wide range ofγ,δ-,δ,ε-,and even more distally unsaturated ketones in good to excellent yields,with H₂ as the sole byproduct.This method features mild reaction conditions,broad functional group tolerance,high regioselectivity.The produced distally unsaturated ketones can be easily converted to other valuable molecules.The second part:Uponβ-scission of alkoxyl radicals,a series of gem-difluoroalkenes with distal carbonyl groups have been constructed by photoredox-catalyzed ring-opening coupling of tertiary alcohols withα-trifluoromethylstyrene.By adjusting the ring size of the cyclic alcohol,γ,δ-,δ,ε-and even more distal carbonyl gem-difluoroolefin derivatives can be regiospecifically produced.The catalytic system features mild reaction conditions and good functional group tolerance,providing a novel and efficient approach for the synthesis of gem-difluoroolefin derivatives.The third part:The visible-light-driven radical alkylation ofα-carbonyl esters using alcohols as alkyl radical precursors has been developed in the absence of any exogenous photocatalysts and oxidants.The transformation is achieved via the formation of xanthates and the subsequent deoxygenation byβ-scission with the assistance of trivalent phosphine under visible light irradiation.This method features mild conditions and high efficiency,providing a novel approach for one carbon homologation of alcohols.In this dissertation,we have developed enriches the toolbox for the application of alcohols as alkyl radical precursors in visible-light-driven radical transformations.These methods feature high efficiency,mild conditions,broad scope,and good functional group tolerance,with the potential for the future industrial applications.