REGIOCHEMICAL CONTROL OF THE RING-OPENING OF 1,2-EPOXIDES BY MEANS OF CHELATING PROCESSES .4. SYNTHESIS AND REACTIONS OF THE CIS-OXIDES AND TRANS-OXIDES DERIVED FROM 3-[(BENZYLOXY)METHYL]CYCLOHEXENE

The synthesis and nucleophilic addition reactions of diastereoisomeric title epoxides cis-7 and trans-8 were studied. While the ring-opening reactions of trans epoxide 8 are rationalized by means of steric, stereolectronic, and conformational arguments, the analogous reactions of cis epoxide 7 indicate the ability of this isomer to react through chelated intermediates when metal salt catalyst is used. In 7 chelation reaction conditions led to a significant increase of nucleophilic attack on the C-1 oxirane carbon; the lack of reversal of the regiochemistry of the ring opening on passing from nonchelating to chelating reaction conditions suggests that cis epoxide 7 reacts through its more stable conformation in both of the two different operating conditions.