Modification of the Fritsch-Buttenberg-Wiechell rearrangement: a facile route to unsymmetrical butadiynes

A modification of the Fritsch-Buttenberg-Wiechell rearrangement has been us ed to form unsymmetrically substituted 1,3-butadiynes from 1,1-dibromo-olef in precursors. The reaction proceeds via lithium-halogen exchange, followed by migration of the aryl or alkynyl moiety to provide the butadiyne framew ork. The facile formation of the dibromo-olefins in three steps from commer cially available aryl aldehydes or carboxylic acid chlorides makes this pro cedure an attractive alternative to traditional methods for butadiyne synth esis. (C) 2001 Elsevier Science Ltd. All rights reserved.