A NEW APPROACH TO THE SYNTHESIS OF N-PROTECTED 2-SUBSTITUTED AND 5-SUBSTITUTED 3-HALOPYRROLES

A new and efficient method for the preparation of N-protected 5-and 2- substituted 3-bromopyrroles 15 and 16 via acid-catalyzed cyclization o f the corresponding acetylenic ketones 6 and acetylenic acetals 14 has been found (Scheme 3). Using this methodology, rapid and quite genera l access to highly substituted pyrroles, which are known to exhibit a number of interesting biological activities, has been established.