Visible Light Induced C-Br and C-N Bonds Activation Reactions

Author:Hu Bei

Supervisor:zhang zhao guo


Degree Year:2016





As a new environment begnin and effective catalytic strategy,visible light-induced photoredox catalysis has been well applied to modern organic synthesis in the recent years.In this dissertation,recent advances in this field were presented in detail and the related visible light-induced C-Br and C-N bond activation reactions were investigated.The dissertation includes:An efficient visible light-induced photoredox reaction of α-brominated carboxylates with enamines via an intermolecular radical addition reaction was developed.The method provided a novel access to various synthetically important γ-ketoesters in good yields under very mild conditions.Based on the above understanding of the mechanism,we have succeeded in the construction of azaspirocyclic cyclohexadienones through visible light-induced intramolecular dearomative cyclization of α-bromo-N-benzyl-alkylamide.This reaction allowed for a highly efficient construction of spirocyclohexadienones under mild conditions in good to excellent yields.a probably mechanism for the reaction was proposed.A photocatalytic intramolecular addition/aryl migration/desulfonylation of 2-bromo-N-aryl-N-(arenesulfonyl)amide has been accomplished.This approach allowed for the construction of a variety of multi-substituted N,2-diarylacetamide without extra reductive quenching additives under mild reaction conditions.In addition,an unprecedented tandem photocatalysis,which consists of two distinct photocatalytic cycles,has been successfully developed.Some control experiments indicated that this novel protocol allowed for a rapid and efficient construction of multisubstituted benzimidazole derivatives through an intramolecular cyclization/deprotection sequence from diamines under very mild conditions.Finally,we have applied the visible light-catalyzed aerobic C-N bond activation to well construct 2-arylpyridines and 2-arylquinolines through cyclization,elimination and aromatization.The applicability of different kinds of simple ketones,easily available primary amines made this transformation very attractive.