Acid-catalysed cyclisations of cyclo-octenylidene derivatives to produce bicyclo[3.3.1]nonanes
Abstract
Heating ethyl (cyclo-oct-4-enylidene)acetate (8) with boron trifluoride–ether complex in benzene gives a mixture of ethyl 1-phenylbicyclo[3.3.1]nonane-9-carboxylate (11) and the corresponding acid (12). Reduction of (11) with lithium aluminium hydride followed by dehydration yields 9-methylene-1-phenylbicyclo[3.3.1]nonane (14) whose structure was confirmed by an independent synthesis.