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

Abstract

(Chemical Equation Presented) Catalytic cyclization of 1,6-allenynes was achieved by AuPPh3SbF6 (5 mol %) in cold CH 2Cl2 (0°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)-π-alkyne, followed by Nazarov cyclization. © 2007 American Chemical Society.