Oxymetallation. Part 12. Further syntheses of monocyclic peroxides via peroxymercuriation

Abstract

The scope of cycloperoxymercuriation as a route to monocyclic peroxides has been investigated by studying the reaction of mercury(II) nitrate with ten representative dienes plus hydrogen peroxide, and with two alkenyl hydroperoxides. By hydrogeno- and bromo-demercuriation of the resultant products, seven new methyl- and bromomethyl-substituted 1,2-dioxacyclo-pentanes and -hexanes have been prepared. The geometrical isomers of three of the 1,2-dioxacyclopentanes (4), (8), and (9) have been separated and assigned cis and trans configurations, and each of the four diastereoisomers of 4-bromo-3-bromomethyl-5-methyl-1,2-dioxacyclopentane (11) has been isolated. Two diastereoisomers of 4-bromo-6-bromomethyl-3-methyl-1,2-dioxacyclohexane (13) are formed and have been separated; their ¹H n.m.r. spectra indicate that each has a chair conformation with equatorial methyl and bromomethyl groups, the stereoisomerism arising from the disposition of the bromine substituent. The byproducts of peroxymercuriation–reduction have been shown to be unsaturated alcohols whose formation is strongly favoured where the cycloperoxymercurial contains an endocyclic mercurio-substituent.