Anomalous reactivity of sodium phenyl selenide

Abstract

Reaction of sodium phenyl selenide generated from benzeneselenol–sodium hydride–tetrahydrofuran with the enone 3 gives the expected conjugate addition product 4 whereas the reagent prepared from diphenyl diselenide–sodium metal–tetrahydrofuran/ultrasound leads to substitution of the bridgehead 13-acetate in 3 to give the 13-phenyl selenide 5. Experimental results for this unexpected observation are in accord with the proposal that the reaction may proceed via an ‘anti-Bredt’ bicyclo[3.2.1]octenone intermediate.