Tetrahedron Letters,Vol.28,No.41,pp 4865-4866,1987 0040-4039/87 $3.00 + .Oo Printed in Great Britain Perqamon Journals Ltd. AN EFFICIENT APPROACH TO ENANTIOMERICALLY PURE FLUORHYDRINS Pierfrancesco Bravo and Giuseppe Resnati CNR - Centro Studio Sostanze Organiche Naturali, Dipartimento di Chimica, Politecnico, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy Abstract: optically pure a'-monofluoro-a-sulphinyl ketones have been reduced with high diastereoselection to give a'-fluoro-a-sulphinylalcohols which upon removal of the sulphinyl residue produced enantiomerically pure fluorhydrins. He have recently described a new approach to differently substituted mono- and poly- fluoro ketones having an optically pure a-sulphinyl group.I We wish to report here that single epimers of a'-monofluoro-a-sulphinyl ketones 1 can - be transformed into enantiomericallypure fluorhydrins 4 through a highly diastereoselective reduction to a-sulphinyl alcohols 2 and removal of the chiral auxilliary sulphinyl group. - Specifically, compounds in which the fluoruinated carbon was a primary one la, a secondary one, and a tertiary one were treated with DIBAH (1.0 N in n-hexane) at -78' C in tetrahy- drofuran solution. Both the (3S,RS)-fluoro ketones lb-h (Rl = H, R2 =CH CH - 3' 2 5' * _ CH2CH2CH(CH3)2, CH2CH=C(CH3)2, C6HS; R' = CH3, n-C3H7, RL = C6HS) and their epimers at the carbon site (3R,RS) li-o were separately reduced alcohols !a-o had the (S) absolute configuration and at in all cases the obtained sulphinyl the created asymmetric centre. 2 The r zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA d .e .39 5% 2 stereochemical course of the reduction process is thus strictly governed by the chirality at 3 the a-sulphinyl auxiliary group, indipendently from the chirality of the at-fluorinated 4865