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Direct Approach to Chiral Propargylic and Allylic Fluorides
H. Jiang, A. Falcicchio, K. L. Jensen, M. W. Paixão, S. Bertelsen, K. A. Jørgensen*
Aarhus University, Denmark
22 June 2009 (online)
Asymmetric α-fluorination of aldehydes 1 with NFSI catalyzed by α,α-diarylprolinol trimethylsilyl ether 2 (0.25-1 mol%) followed by in situ homologation of the intermediate α-fluoro aldehydes 3 under either Ohira-Bestman conditions or by a Wittig reaction provides direct access to optically active terminal propargylic fluorides 4 or allylic fluorides 5, respectively, in good yields along with high enantioselectivities. Moreover, functionalization of propargylic fluorides 4 by click-chemistry giving optically active triazoles is presented.