An Efficient Highly Regioselective Synthesis of 2,3,4-Trisubstituted Pyrroles by Cycloaddition of Polarized Ketene <i>S</i>,<i>S-</i> and <i>N</i>,<i>S-</i>Acetals with Activated Methylene Isocyanides

Abstract

An efficient route for regioselective synthesis of 2,3,4- substituted pyrroles allowing precise control over the introduction of a number of substituents and functionalities (tosyl, carbalkoxy, aryl, cyano, nitro, acetyl, benzoyl, cyclic amines, etc.) at the three positions of the pyrrole ring has been developed via 1,3-dipolar cycloaddition of readily accessible polarized ketene S,S- and N,S-acetals with carbanions derived from activated methylene isocyanides.