Additive-assisted Rupe rearrangement of 1-ethynylcyclohexan-1-ol in near-critical water

We performed the Rupe rearrangement of 1-ethynylcyclohexan-1-ol in near-critical water to study the reaction under high temperature conditions. The final product thus obtained was primarily 1-cyclohexen-1-ylethanone which was identified by GC-MS. The influences of reaction time, temperature, and initial reactant-to-water ratio on the yield of 1-cyclohexen-1-ylethanone were examined. The yield of 1-cyclohexen-1-ylethanone was 49 % in pure water at 260 degrees C for a reaction time of 60 min. However, when additives such as ZnSO(4), FeCl(3), and NaHSO(4), respectively, were introduced to the water to investigate the effect of salts on the Rupe rearrangement reaction, the yield increased markedly to as much as 88 % in 5 mole % NaHSO(4) aqueous solution under the same conditions. The catalytic ability of the additives decreased in order: NaHSO(4), FeCl(3), ZnSO(4). On the basis of these results, a possible reaction mechanism of the Rupe rearrangement of 1-ethynylcyclohexan-1-ol in near-critical water was proposed. (C) 2011 Institute of Chemistry, Slovak Academy of Sciences