Visible-Light Photoredox Catalyst Difunctionalization Of Unsaturated Bonds

Difunctionalization of unsaturated bonds is an important method to introduce some important functional groups in organic molecules,in which the transition metal plays an irreplaceable role in the difunctionalization of unsaturated bonds.In recent years,the development of difunctionalization of the unsaturated bond by the visible light catalytic strategy has been developed rapidly.Compared with the conventional method,it has the characteristics of atom economy and environmental friendliness.Most photoredox reaction proceed under room temperature and light source is typically household light bulb,LEDs or sunlight.In addition,the photocatalyst is offen employed at low loadings(less than 1.0%mmol).In general,visible light photoredox catalysis already become a green,efficient and low energy consumption synthetic stategy and will promote the development of clean chemical industry.This dissertation includes five parts.In the first part:We developed the carbofluoroalkylation of homopropargylic alcohols through visible light promoted radical 1,4-aryl migration with 2-bromo-2,2-difluoroacetate as CF2 source.The easily available homopropargylic alcohols can undergo 1,2-aryl migration,providing an efficient method for the synthesis of difluoroalkyl-substituted olefins.In the second part:We developed a visible-light photoredox-catalyzed cascade annulation of 2-ethynylaldehyde hydrazones with α-bromo-carbonyls for the synthesis of various polycyclic compounds.This protocol is characterized by a broad substrate scope and mild conditions,providing an efficient method for the synthesis of polycyclic compounds.In the third part:We developed a photosensitizer-free,highly efficient sunlight-promoted tandem[3+2]/[4+2]annulation of unsaturated α-bromocarbonyls with o-alkynylanilines,and allowed for convenient synthesis of fused benzobicyclic skeletons.The reaction was clean and practical in mild conditions.A mechanistic investigation is present based on control experiments.In the fourth part:The first catalytic inverse hydroboration of imines with N-heterocyclic carbene boranes has been realized by means of cooperative organocatalysis and photocatalysis.The radical-radical C-B cross-coupling driven by persistent radical effect and the B-centered radical addition to imines are possible and a radical chain pathway is less likely.In the last part:we developed a novel one-pot synthesis of sulfone-containing 4-quinolones with easily available sulfinic acids as sulfonylating precursors.This reaction is characterized by mild reaction conditions,high functional-group tolerance and amenability to gram-scale synthesis.