Enantioselective synthesis and circular dichroism of endocyclic allenes

Abstract

The novel, enantiomerically enriched nine- and ten-membered cyclic allenes (+)-5a-c and (-)-6a-c were synthesized by lipase-catalyzed kinetic resolution of propargylic acetates 1/2 and subsequent anti-stereoselective S N2′-substitution with magnesium cuprates. The CD spectra of these allenes exhibit distinct features that are a function of the ring size and the alkyl substituent at the allene moiety. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.