Oxidation of oct-1-ene and trans-oct-4-ene by lead(IV), thallium(III), and mercury(II) acetates

Abstract

The comparative study of the oxidation of oct-1-ene by lead(IV), thallium(III), and mercury(II) acetates in methanol has been extended to other solvents and to the oxidation of an internal olefin, trans-oct-4-ene. The general rules developed for the methanol system are found to be applicable to these solvents. In acetic acid, incorporation of an acetoxy-substituent on C-2 of oct-1-ene followed by decomposition of the organometallic adduct via an acetoxonium ion gives a high yield of hydroxy-acetates. This yield is boosted in lead(IV) oxidations by the addition of water to the system. The adduct from mercury(II) oxidation is stable but reduction of it with borohydride does not appear to offer a clean means of adding a carboxylic acid across a double bond: substantial reduction of the ester function occurs. There appear to be severe steric constraints to the oxidation of trans-oct-4-ene by initial electrophilic addition of the metal acetates but when this does occur there is a stereoselective preference for anti-addition. However, the major products are allylic. It is suggested that, in the case of lead(IV) oxidations, these arise by a homolytic process; indeed there is no evidence of heterolytic attack of this oxidant on oct-4-ene.