Mechanism of the boron trifluoride-catalysed cyclisation of some cyclo-octenylidene derivatives

Abstract

The conversion of ethyl cyclo-oct-4-enylideneacetate (1) into ethyl 1-phenylbicyclo[3.3.1]nonane-9-carboxylate (2) and the corresponding acid (3) by boron trifluoride–ether complex in benzene has been investigated, and a mechanism is suggested. Ethyl (1-phenylcyclo-oct-4-enyl)acetate (11) and ethyl 5-phenylcyclo-octylideneacetate (10) have been synthesised; examination of their separate reactions with boron trifluoride–ether in benzene shows that neither is an intermediate in the conversion.