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An improved coupling procedure for the barton-zard pyrrole synthesis

✍ Scribed by Pavel Bobál; David A. Lightner

Publisher
Journal of Heterocyclic Chemistry
Year
2001
Tongue
English
Weight
38 KB
Volume
38
Category
Article
ISSN
0022-152X

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✦ Synopsis

Abstract

An improved final step in the Barton‐Zard pyrrole synthesis uses inexpensive potassium carbonate as base in the coupling‐cyclization reaction of vic‐nitro‐acetates with isocyanides. In this modification the isolated yields of synthetically useful 2‐carboalkoxypyrroles (1a,b and 3) and 2‐(p‐toluenesulfonyl)pyrroles (2a,b) consistently rise to the 78‐89% range. Conversion of 2a to 5‐(p‐toluenesulfonyl)‐2‐pyrrolinone 4 is conveniently and directly achieved by reaction with 30% hydrogen peroxide in acetic acid, thus circumventing the commonly used two step procedure involving bromination followed by solvolysis.

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