Perepoxide intermediates in the conversion of some β-halohydroperoxides to allylic hydroperoxides by base

Abstract

Migration of the hydroperoxy group occurs during the reaction between base and several β-halohydroperoxides to give allylic hydroperoxides. An 86:14 ratio of 3-hydroperoxy-2-(4-methoxyphenyl)-3-methyl-1-butene-3-hydroperoxy-3-(4-rnethoxyphenyl)-2-methyl-1-butène was formed in 90% yield from 2-bromo-3-hydroperoxy-3-(4-methoxyphenyl)-2-methyibutane. From 1-chloro-, 1-bromo-, and 1-iodo-1-(1-hydroperoxy-1-methylethyl)cyclohexane there were obtained 1-(1-hydroperoxy-1-methylethyl)cyclohexene and 1-hydroperoxy-1-(2-propenyl)cyclohexane in ratios of 93:7, 94:6, and 94:6, respectively, in 98–100% yieid. Isopropylidenecyclohexane was converted with singlet oxygen to these allylic hydroperoxides in a 10:90 ratio. Only the latter allylic hydroperoxide was formed in the reaction between the alkene and triphenyl phosphite ozonide at −70 °C. The p-nitrobenzoate esters of 1-hydroperoxy(1-chloro-, 1-bromo-, and 1-iodo-1-methylethyl)cyciopentane were converted quantitatively to 1-(1-hydroperoxy-1-methylethyl)cyclopentene and 1-hydroperoxy-1-(2-propenyl)-cyclopentane in 77:23, 73:27, and 70:30 ratios, respectively. Oxidation of isopropylidenecyclopentane with triphenyl phosphite ozonide at −70 °C and singlet oxygen produced the allylic hydroperoxides in 62:38 and 58:42 ratios, respectively. The reactions of the β-halohydroperoxides proceed exclusively via perepoxide intermediates. The reactions between the alkenes and singlet oxygen or triphenyl phosphite ozonide do not involve perepoxide inter mediates.