Palladium-Catalyzed Heck-Type Cyclization And Carbonylation For The Synthesis Of Functionalized Thioesters/Amides And Bisheterocycles

Thioesters,amides,and heterocycles are very important compounds in organic chemistry.They are present as main structures in various natural products and bioactive compounds,and play important roles in pharmacological actions and material innovations.In recent decades,much efforts have been put in the preparation of thioesters,amides,and heterocycles,and great progress has been achieved in this field.However,some drawbacks,such as narrow substrate scope,harsh reaction conditions,and complex synthetic process remain exist.Therefore,the development of simple,economic,and efficient strategies for the synthesis of these compounds are of great research significance.In recent years,palladium-catalyzed Heck cyclization and carbonylation has become one of the most important tools for the synthesis of complex carbonyl-containing compounds and heterocycles.σ-alkylpalladium complex,which is generated from Heck cyclization and carbonylation could be trapped by CO moiety and then undergo further transformation to afford cyclic carbonyl-containing compounds.It has been widely used in the construction of cyclic molecules.Considering the importance of thioesters,amides,and heterocycles,as well as the synthetic advance of Heck cyclization and carbonylation reactions,palladium-catalyzed Heck cyclization and carbonylation for the synthesis of functionalized thioesters/amides and bisheterocycles have been explored,the main contents are shown as follows:Palladium-catalyzed cascade Heck-type cyclization and carbonylation for the access of functionalized thioesters has been developed.Using odorless and readily available arylsulfonyl chlorides as the sulfur sources,with Mo（CO）₆ as both CO source and reductant,a variety of thioesters bearing（iso）chroman structures were obtained in moderate to good yields with good functional group compatibility.The reaction conditions are mild,avoiding the use of toxic CO gas,and without additional reductant,which make this strategy more promising in the construction of functionalized thioesters.Palladium catalyzed cascade Heck-type cyclization and reductive aminocarbonylation for the synthesis of functionalized amides has been developed.Using cheap and readily accessible nitroarenes as promising nitrogen precursors,a variety of amides bearing（iso）chroman moieties including benzofive-,six-,and seven-member ring structures were obtained in moderate to good yields with good functional group compatibility.Furthermore,a late-stage modification of natural molecules is achieved by this approach.Palladium-catalyzed domino carbopalladation/carbonylative cyclization to access heterocycles bearing oxindoles and 3-acylbenzofuran/3-acylindole moieties has been developed.Using TFBen as efficient and convenient CO source,a wide range of heterocycles bearing oxindoles and 3-acylbenzofurans/3-acylindole molecules were prepared in moderate to excellent yields with good functional group tolerance.This protocol features the formation of three C-C bonds and one C-O/C-N bond in a single one-step operation,and provides a novel pathway to access carbonyl-containing compounds bearing bisheterocyclic skeletons.