Cationic cyclization involving a remote allene function in the trifluoroethanoluysis of hepta-5,6-dienyl toluene-p-sulphonate

Abstract

The remote allene function participates efficiently in the trifluoroethanolysis of hepta-5,Gdienyl toluene-fi-sulphonate, leading to the cyclized Z-methylenecyclohexyl cation. CATIONICcyclization reactions of general type (1) -+ (2) play a central role in the biogenesis of cholesterol and other steroidal compounds,l and are also useful in syntheses of mono-and poly-cyclic molecules.2 Recently it has been (6 1 (7 1 discovered3 that remote triple bonds can participate in olefinic cyclizations4 [(3) --+ (4) + ( 5 ) ] , and this reaction has also been found to be synthetically u ~e f u l . ~ Since allenes