Oxymetallation. Part IV. The reaction of derivatives from the t-butyl-peroxymercuration of αβ-unsaturated esters and ketones with sodium borohydride

Abstract

Reduction by sodium borohydride of the compounds XHgCH₂CMe(OOBu^t)COY, formed by t-butylperoxy-mercuration of isopropenyl methyl ketone (Y = Me) and methyl methacrylate (Y = OMe), affords the previously unknown α-carbonyl-substituted peroxides Me₂C(OOBu^t)COY mixed with 10 and 30 mole % respectively of the corresponding epoxides. Similar treatment of the compounds R¹R²C(OOBu^t)CH(HgOAc)CO₂Me, obtained from four αβ-unsaturated esters, gives cleanly and in high yield the β-methoxycarbonyl-peroxides R¹R²C(OOBu^t)-CH₂CO₂Me, and represents a generalised and much improved synthesis of this type of compound. In contrast the related peroxymercurial from chalcone (PhCHCHBz) gives a high yield of chalcone oxide and that from mesityl oxide affords mainly the dialkylmercurial, [Me₂C(OOBu^t)CH(COMe)]₂Hg. The methoxymercurials from chalcone and mesityl oxide R¹R²C(OMe)CH(HgOAc)COR, are similarly symmetrised under these conditions.