A versatile synthetic route to dehydrobenzoannulenes via in situ generation of reactive alkynes

This paper outlines the development of a protocol that allows in situ gener ation of unstable alkynes under Pd-catalyzed cross-coupling conditions. Cu- mediated intramolecular cyclization of the resultant alpha,omega -polyynes provides dehydrobenzoannulenes as singular species, in very good overall yi elds, and in a variety of topologies that are inaccessible by traditional r outes or previously available in low yield only. In addition, we will discu ss the solid-state structure and reactivity of these macrocycles, as well a s the ability of the planar dehydrobenzoannulenes to support weak induced r ing currents. (C) 2001 Elsevier Science Ltd. All rights reserved.