Palladium-Catalyzed Approach for the General Synthesis of (<i>E</i>)-2-Arylmethylidene-<i>N</i>-tosylindolines and (<i>E</i>)-2-Arylmethylidene-<i>N</i>-tosyl/nosyltetrahydroquinolines: Access to 2-Substituted Indoles and Quinolines

Abstract

A facile and efficient method for the synthesis of (E)-2-arylmethylidene-N-tosylindolines and (E)-2-arylmethylidene-N-tosyl/nosyltetrahydroquinoline variants has been developed through palladium-catalyzed cyclocondensation of aryl iodides with readily available 1-(2-tosylaminophenyl)prop-2-yn-1-ols and their higher homologues, respectively. The proposed reaction mechanism invokes the operation of trans-aminopalladation during cyclization (5/6-exo-dig), which ensures exclusive (E)-stereochemistry in the products. The method is fast, operationally simple, totally regio- and stereoselective, and versatile enough to access a variety of 2-substituted indoles and quinolines. The reactions proceeded efficiently with a wide variety of substrates and afforded the corresponding products in moderate to excellent yields.