Study On N-Heterocyclic Carbenes And Photoredox Dual-Catalyzed Radical Acylative Difunctionalization Of Carbon-Carbon Multibonds

Carbonyl compounds are important chemical feedstocks and widely exist in agriculture and functional materials.The construction of carbonyls was an important research area in organic synthesis.Unsaturated hydrocarbon is an important synthon in organic synthesis.The radical acylative difunctionalization of carbon-carbon multibonds could introduce two functional groups into the π-system,regarded as a powerful synthesis strategy for carbonyl compounds.The radical reaction has features of high reactivity,insensitivity to steric hindrance and good compatibility of functional groups,and become a powerful tool to build new chemical bonds.Radical cross-coupling between two carbon radicals has emerged as a powerful platform for constructing C–C bonds and has received increasing attention.Since the radical–radical coupling reactions proceed in a diffusion-controlled manner,selectivity control was a critical challenge.NHCs could stabilize the acyl radicals and open a new avenue for radical acylation chemistry.Despite those innovative approaches,NHC-catalyzed radical transformations have mainly been focused on coupling with alkyl radical species,and cross-couplings with other highly active carbon-centered radicals were still highly desirable.In this thesis,we developed radical acylative difuntionalization of carbon-carbon multi-bonds via NHCs/PC dual-catalyzed radical-radical cross-coupling of NHCsderived ketyl radicals with other carbon-centered radicals.We have realized 1,4-sulfonyl acylation of 1,3-enynes and 1,2-sulfonyl acylation of allenes via crosscoupling of an acyl radical with allenyl radical or allyl radical.The synthetic value of1,4-sulfonyl acylation of 1,3-enynes were further highlighted by the construction of hetero-1,3,5-tri-substituted benzene.We also realized the selective installation of two similar acyl radicals to olefins by modulating the reactivity of acyl radicals.The details are as follows:1.We have developed visible light-mediated NHCs/PC co-catalyzed radical 1,4-sulfonyl acylation of 1,3-enynes,providing structurally diversified Sulfone-containing allenyl ketones.Mechanistic studies indicated that the key step of the transformation is allenyl and ketyl radical cross-coupling.This versatile protocol features mild conditions and broad functional group tolerance,56 cases of allenyl ketones were synthesized with up to 98% yield.2.We realized a DBU-mediated isomerization/6-π electro-cyclization/oxidative aromatization cascade of α-sulfonyl-substituted allenyl ketones under an air atmosphere.This versatile protocol featuring easy operation,and broad functional group tolerance provides a new avenue for the construction of hetero-1,3,5-trisubstituted benzene.3.We have developed NHCs/PC co-catalyzed radical 1,2-sulfonyl acylation of allenes via an unprecedented cross-coupling between an NHC-stabilized acyl radical and a delocalized allyl radical.This versatile protocol provides an attractive strategy for valuable sulfonyl-containing allyl ketones under extremely mild conditions with broad functional group tolerance,providing an attractive strategy for value-added sulfonyl-containing allyl ketones.4.By distinguishing two similar carbonyl groups,we developed NHCs/PC cocatalyzed three-component radical 1,2-dicarbonylation of alkenes.Distinct reactivity of acyl radical and NHCs-stabilized ketyl radical contribute to excellent selectivity control.Transient acyl radicals underwent rapid addition to alkene delivery alkyl radicals,which are trapped by NHCs-stabilized ketyl-type radicals,affording 1,2-dicarbonylation products.This transformation features mild reaction conditions,and good functional group tolerance,and excellent selectivity,providing a practical approach for the 1,2-dicarbonylation of olefins.