REGIOSELECTIVE OPENING OF EPOXYALDONOLACTONES TO FLUORODEOXYALDONOLACTONES USING TETRABUTYLAMMONIUM DIHYDROGENTRIFLUORIDE

A study on the hydrofluorination of epoxyaldonolactones with Bu4N+H2F3- (1) under solid-liquid PTC and homogeneous conditions has been performed. Unsubstituted 5,6-epoxy-hexono-1,4-lactones 2a give the corresponding fluorohydrins in high yield using catalytic amounts of 1 and an excess of solid KHF2, while an equimolar amount of 1 is used with 2,3-epoxyaldonolactones 2d-g and 5,6-epoxy-hexono-1,4-lactones containing a free hydroxy group 2b,c. In all cases the reaction is completely regio- and stereoselective affording 6-deoxy-6-fluoro-hexonolactones 3a,b and 2-deoxy-2-fluoro-aldonolactones 3d,f.