Visible-Light-Induced Radical Carbonylation

Carbon monoxide is one of the most import.ant C1 resource in synthesis chemistry.It has a wide range of sources and play a very important role in the synthesis of large industrial products and fine chemicals.Traditional carbonlylation reactions always need heating or high energy ultraviolet irradiation.Despite recent advances,strong demand still exists for alternative strategies which is more efficient with lower energy consumption under milder conditions.In this thesis,we review the advancement in carbonylation with carbon monoxide,especially radical carbonylation,and introduce the advance of visible light photoredox catalysis.Then,with the designed autoclave for high-pressure photochemical reactions(Chinese patent:ZL 201420613785.5),a series of visible-light-induced raidical carbonylation reactions were investigated.Firstly,the first radical alkoxycarboxylation of aryldiazonium salts using CO gas through visible light-induced photoredox catalysis was developed.This reaction is entirely base-and metal-free,carried out at room temperature with a low loading of organic dye as a photocatalyst(0.5 mol%),and provides a wide range of arylcarboxylic acid esters in high chemical yields.Importantly,this photocatalytic system can be successfully extended to other carbonylation reactions,such as the synthesis of 9-fluorenone starting from 2-phenylphenyldiazonium salt.Secondly,direct radical decarboxylative carbonylative alkynylation reactions of carboxylic acids was successfully developed through visible light photoredox cacatlysis.These reactions allow the preparation of various ynones in good to excellent yields under very mild conditions.Various carboxylic acids including primary,secondary and tertiary ones are tolerant in the carbonylation reactions.The functional group in the substrates also have little influence on the efficiency of the reaction.Finally,a visible-light-induced radical cyclocarbonyltion of alkenylamines and alkyl bromides to lactams was achieved.Under the optimized conditions,β-lactam,y-lactams,δ-lactams and 3,4-dihydroquinolin-2(1H)-ones could be prepared in good to excellent yields.Pyroquilone derivative can also be prepared in moderate yield.This reaction could be conducted under mild condition with low catalyst loading(0.2 mol%).