REGIOSELECTIVE AND STEREOSELECTIVE FORMATION OF TRISUBSTITUTED AND TETRASUBSTITUTED TETRAHYDROFURANYLIDENES FROM HYDROXY KETOSULFONES

Four tri- and tetrasubstituted E-1-(benzenesulfonyl)-1-tetrahydrofuran ylidenes 7-10 were synthesized from their corresponding alpha'-benzene sulfonyl-gamma-hydroxyketones 1 in good yields. The examination of the regio- and steroselectivity of these thermally induced reactions show s preference for both, the exocyclic nature of the double bond and the E-geometry in all tetrahydrofuranylidenes described. Structural assig nments are based on infrared, H-1 nmr, C-13 nmr, 2D H-1-H-1 and C-13-H -1 correlation spectra. In contrast to tetrahydrofuranylidenes 7-10, h emiketal 6 shows no tendency towards dehydration under the thermal rea ction conditions used. This paper discusses the extent and limitations of this method as a tool of synthetic utility for the regio- and ster eoselective preparation of the target compounds.