Permanganate–periodate oxidation. Part VIII. The oxidation of some cyclic mono-olefins and monoterpenes

Abstract

The reaction of cyclic mono-olefins with the permanganate-periodate reagent was investigated. 4-Terpinenol and its acetate, and to a lesser degree a-terpineol and ca~nphene gave in addition to the expected products, several neutral and acidic products. In contrast, a-pinene, P-pinene, sabinene, pulegone, and several cyclo-olefins which can be considered as simple analogues of these monoterpenes, afforded the predicted products in high yield. Cyclo-hexanone and menthone, though saturated, were oxidized extensively, enolization offering a plausible pathway for this result. Saturated terpene alcohols reacted only very slowly indicating that attack at a tertiary hydrogen is not a significant part of the permanganate-periodate reaction.Canadian Journal of Chemistry, 47, 3682 (1969) IntroductionRecently we have shown that the common acyclic monoterpenes may be oxidized by the permanganate-periodate reagent in high yield to predicted end products (I). In a preliminary experiment it was found that a-terpineol did not give a high yield of the expected product, homoterpenyl methyl ketone. In view of this, and of the different behavior of some dienes as reported recently by Klein and Rojahn (2), Apsimon et al. (3), and von Rudloff (4), the oxidation of some cyclic monoterpenes and related cyclo-olefins was studied with the specific purpose of determining whether or not the cyclic mono-olefins, and in particular monoterpenes, would react as predicted with the permanganate-periodate reagent.Daly and co-workers (5) have employed the reagent in a preparative oxidation of sabinene to yield sabina ketone. We reported briefly (6) on the excellent yields of sabina ketone and nopinone which may be obtained from sabiilene and P-pinene respectively, and that the oxidation proceeds at a satisfactory rate in aqueous suspension. Our previous studies (1,(7)(8)(9)(10)(11)(12) have shown that the oxidation of an olefinic double bond proceeds in a predictable manner, involving hydroxylation of the double bond by a permanganate ion (via a TC complex and hypomanganate ester (13) (see also Wiberg and Geer (14)), followed by periodate cleavage of the diol or ketols thus formed, and subsequent slower oxidation of the resulting