Oxymetallation. Part 14. Modified procedures for t-butyl peroxymercuriation and bromodemercuriation that lead to an improved, stereoselective, conversion of non-terminal alkenes into β-bromoalkyl peroxides

Abstract

Stereospecific trans-peroxymercuiation of non-terminal alkenes with little or no accompanying acyloxymercuriation has been accomplished by using mercury(II) acetate under conditions of equilibrium control induced by the presence of 20 mol% of perchloric acid. Bromodemercuriation of the derived peroxymercurials, using bromine in methanol with added sodium bromide, stereoselectively affords β-bromoalkyl peroxides with predominant retention of configuration. Neither of the modified procedures is effective in improving the preparation of peroxides derived from norbornene. Ten diastereoisomerically pure bromoperoxides have been isolated by silica chromatography and characterised by ¹³C n.m.r. spectroscopy. Configurations have been assigned to the cyclohexene and norbornene derivatives on the basis of their 200 MHz ¹H n.m.r. spectra.