CYCLOHEXANE COMPOUNDS: V. THE REACTION OF 1-METHOXYCYCLOHEXENE-2 WITH AQUEOUS N-BROMOSUCCINIMIDE. THE 1-METHOXY-2-BROMO-3-HYDROXYCYCLOHEXANES

Interaction of 1-methoxycyclohexene-2 and aqueous N-bromosuccinimide gave a mixture of stereoisomeric bromohydrins, which, on treatment with aqueous sodium hydroxide, furnished 1β-methoxy-2α,3α-epoxycyclohexane (I) and 1α-methoxy-2α,3α-epoxycyclohexane (II) in the ratio 3:1. The mixture from the N-haloimide-olefin reaction was separated by preparative vapor phase chromatography into three isomeric bromohydrins, 1α-methoxy-2α-hydroxy-3β-bromocyclohexane (IV), 1α-methoxy-2α-bromo-3β-hydroxycyclohexane (V), and 1α-methoxy-2β-bromo-3α-hydroxycyclohexane (VI) in the relative proportions 1:10:4. The 3-bromo isomer IV was identified by comparison with an authentic specimen prepared by the action of hydrobromic acid on the oxide II. Compounds V and VI were shown to have the indicated structures by deetherification to the corresponding bromodiols VII and VIII in high yield, followed by debromination of the latter to trans- and cis-1,3-cyclohexanediol respectively. The product distribution is considered in relation to the intervention of electronic and steric factors in a possible mechanism suggested for the reaction between aqueous N-bromosuccinimide and 1-methoxycyclohexene-2.