Convergent Routes to Pyrroles Exploiting the Unusual Radical Chemistry of Xanthates - An Overview

Convergent routes to a variety of pyrroles involving radical additions of xanthates are described. Emphasis is placed on reactions leading to the formation of 1,4-diketones or 1,4-ketoaldehydes or their synthetic equivalents, which can then be condensed with ammonia or primary amines in a variation of the classical Paal-Knorr synthesis of pyrroles. The modification of pyrroles by direct radical addition is also discussed. 1 Introduction 2 Earlier Routes to Pyrroles 3 The Xanthate Radical Addition-Transfer Process 4 Application to Pyrrole Synthesis 5 Further Variations 6 Direct Modification of Existing Pyrrole Rings 7 Outlook and Perspectives.