Asymmetric Nucleophilic Monofluorobenzylation of Carbonyl Compounds: Synthesis of Enantiopure vic-Fluorohydrins and a-Fluorobenzylketones

Asymmetric nucleophilic monofluoroalkylation of a broad range of aldehydes with an a-fluoro-?-sulfinylbenzyl carbanion takes place with complete control of the facial selectivity at the carbanion and good to high anti-diastereoselectivity to give easily separable mixtures of two optically pure 1,2-fluorohydrin derivatives (up to 24:1 anti/syn). Separation and removal of the p-tolylsulfinyl group with tBuLi provides enantiomerically pure anti-1,2-disubstituted-1,2-fluorohydrins, whereas a-fluorobenzylketones can be obtained by desulfinylation of the mixture followed by pyridinium chlorochromate oxidation (one-pot process).