Water → 6,9-Dimethyl-5,6,7,8,9,10-hexahydro-6,9-methanobenzocycloocten-11-one

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Reaction Steps

α,α'-Dibromoxylene (30.3 g., 0.115 Mole) is dissolved in dry acetonitrile (250 ml.) and then, under nitrogen, the pyrrolidine enamine of 2,5-dimethylcyclopentanone (prepared from 2,5-dimethylcyclopentanone and pyrrolidine via the method of Stork) is added dropwise over one-half hour. The mixture is refluxed 2 days, cooled, water (100 ml.) is added; and the mixture is refluxed 1 hour, cooled, concentrated in vacuo, then extracted with ether (3×75 ml.). The combined extracts are washed with 10% HCl (50 ml.), brine (50 ml.), then dried and evaporated to yield 16 g. of solid, which recrystallized from dichloroethane-hexane gives pure title compound (9.7 g.). The mother liquors are chromatographed on silica gel (100 g.), eluting with ether-hexane (1:4) to give 5.8 g. more title compound, which yields 4.9 g. pure on crystallization from ether-hexane (64% total yield), m.p. 134°-135° C.

Provenance & Evidence