Stereospecific benzylic dehydroxyfluorination reactions using Bio's TMS-amine additive approach with challenging substrates

Reactions involving the conversion of a benzylic alcohol into a benzylic fluoride using RSF3 reagents are notoriously difficult to achieve with high stereochemical inversion (S(N)2 reaction) due 70 competing dissociative S(N)1 reaction processes. This Letter develops the methodology of Bio et al., and reports that the addition of a preformed 1:TMS-amine 1:RSF(3) (fluorination reagent) complex as the reagent in these reactions significantly suppresses the S(N)1 process and promotes a highly stereospecific reaction generating benzylic fluorination products of high %ee. (C) 2010 Elsevier Ltd. All rights reserved.