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 generation 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 yields, and in a variety of topologies that are inaccessible by traditional routes or previously available in low yield only. In addition, we will discuss the solid-state structure and reactivity of these macrocycles, as well as the ability of the planar dehydrobenzoannulenes to support weak induced ring currents. (C) 2001 Elsevier Science Ltd. All rights reserved.