Gold-catalyzed synthesis of bicyclo[4.3.0]nonadiene derivatives via tandem 6-endo-dig/Nazarov cyclization of 1,6-allenynes

J Org Chem. 2007 Aug 31;72(18):6753-7. doi: 10.1021/jo0707939. Epub 2007 Aug 3.

Abstract

Catalytic cyclization of 1,6-allenynes was achieved by AuPPh(3)SbF(6) (5 mol %) in cold CH(2)Cl(2) (0 degrees C, 0.5-4 h) to form bicyclo[4.3.0]nonadiene products; this cyclization proceeded more efficiently for a substrate bearing R = alkyl (yields >70%). We propose a reaction mechanism involving a 6-endo-dig cyclization of Au(I)-pi-alkyne, followed by Nazarov cyclization.