REGIOCHEMICAL CONTROL OF THE RING-OPENING OF AZIRIDINES BY MEANS OF CHELATING PROCESSES - SYNTHESIS AND RING-OPENING REACTIONS OF CIS- AND TRANS-AZIRIDINES DERIVED FROM 4-(BENZYLOXY)CYCLOHEXENE

The regiochemical outcome of the ring opening of aziridines bearing a polar remote functionality was verified in a conformationally semirigid bicyclic system in which the polar functionality (OBn) is in an homoallylic relationship to the aziridine ring. The couples of diastereoisomeric unactivated cis-3 and trans-4 and activated aziridines cis-5 and -7 and trans-6 and -8 derived from 4-(benzyloxy)-cyclohexene were prepared, and some of their opening reactions were studied. The regioselectivity observed in the opening reactions of the cis derivatives turned out to depend largely on the opening (standard, strongly acidic, or metal-assisted) reaction conditions, thus providing a nice regioalternating process. The results obtained are rationalized by admitting the incursion of chelate bidentate intermediate structures in which the proton or the metal is actively involved.