Palladium-catalyzed Synthesis Of Quinoline Carboxylic Esters

In recent years,palladium-catalyzed carbocyclization reactions involving CO represents an ideal and straightforward method for the synthesis of carbonyl-containing heterocyclic derivatives.However,there are still some problems,such as the harsh conditions and limited substrates.Therefore,the development of efficient carbocyclization carbonylation reactions for the synthesis of heterocyclic compounds is still a desirable goal.Hydroamination has attracted considerable attention owing to the high atomic utilization.In the past decades,numerous reports have been developed.The use excess metal catalysts or acid-base system limited the development.Therefore,it is still of great significance to develop a simple and effective catalytic system for the hydroamination reaction.This paper reviews the progress of palladium-catalyzed intramolecular cyclization carbonylation reaction and hydroamination reaction to access heterocyclic carboxylic acid esters and pyrazole derivatives.We have overcome some challenges such as proto-depalladation to generate quinoline byproduct and use carbon as weak nucleophile in the first reaction.Besides,the use of a small amount of catalyst can achieve intramolecular hydrogenation conversion in the second reaction.