Optically pure methyl 4-methylphenyl sulphoxide and ethyl 4-methylphenyl sulphoxide are metallated with lithium diisopropylamide and then subjected to the reaction with fluorinated lithium acetates or acetic esters. C-Acylation proceeds smoothly and regioselectively to give high yields of chiral 3-fluorinated 2-oxopropyl 4-methylphenyl sulphoxides. The analogous reaction of dimethyl sulphoxide with fluorinated lithium acetates affords good yields of racemic 3-fluorinated 2-oxopropyl methyl sulphoxides. As examples of further reactions of the products, C-methylation, S-deoxygenation, and carbonyl reduction of 3-fluoro-2-oxopropyl 4-methylphenyl sulphoxide are described.
optically active sulphenyl and sulphonyl fluorohydrins were obtained by reduction of ketones with baker's yeast or by enzymatic resolution of their racemic esters using Candida cylindracea lipase. Crystallization of partially optically active fluorohydrins gave enantiomerically pure forms. Enantioselectivity of the enzymatic reactions is affected by steric requirements of the substituents.