REACTIONS OF 1,3-DIOXOLANES WITH IODINE MONOCHLORIDE - FORMATION OF CHLOROHYDRIN ESTERS AND DIOL MONOESTERS

2-Mono-substituted 1,3-dioxolanes are oxidised by iodine monochloride to the appropriate 2-substituted 1,3-dioxolan-2-ylium ions, whose stability is dependent upon the presence and nature of substituents on C-4 and C-5. Some dioxolanylium ions are labile and under the reaction conditions afford chlorohydrin esters, with inversion of configuration taking place at the ring carbon attacked by chloride. Others are stable under the reaction conditions and may be converted on aqueous workup to diol monoesters with retention of configuration at C-4 and C-5. The effect of substituents and reaction conditions on these competing reactions are described. The stereo- and regio-chemistry of both hydroxy- and chloro-ester formation was confirmed through NMR studies, which necessitated the prior detailed analysis of the H-1 and C-13 spectra associated with the acyloxy sidechains of the relevant esters.