δ-Fluoro and δ,δ-difluorohomoallylic alcohol derivatives can be efficiently prepared by LiAlH4 reduction of the δ,δ-difluoroallylic alcohols and the γ-chlorodifluoromethylallylic alcohols, respectively, through regioselective SN2′ reaction, in which the free hydroxyl group is essential for the reaction to proceed.
Cu(I)-mediated alkyl-transfer reaction of trialkylaluminum (R3Al) with (E)- or (Z)-4,4-difluoro-5-hydroxyallylic alcohol derivatives proceeded in an SN'-type manner to give the corresponding 2-alkylated (Z)-4-fluoro-5-hydroxyhomoallylic alcohol derivatives with 2,5-syn- or 2,5-anti selectivity, respectively. Oxidation of the primary hydroxyl group of the product to carboxylic acid was easily achieved without epimerization at the chiral centers. (C) 2002 Elsevier Science Ltd. All rights reserved.
An Efficient and General Route to <i>g</i><i>em</i>-Difluoromethylenated α,β-Unsaturated δ-Lactones: High Enantioselective Synthesis of <i>g</i><i>em</i>-Difluoromethylenated Goniothalamins
An efficient and general strategy to gem-difluoromethylenated α,β-unsaturated δ-lactones in high yields from various aldehydes (including aliphatic, aromatic, α,β-unsaturated, and sterically hindered aldehydes) has been developed. This methodology was successfully applied for the preparation of two enantiomers of gem-difluoromethylenated goniothalamins (S)-1 and (R)-1. gem-Difluoropropargylation of
Stereoselective synthesis of (Z)-fluoroalkenes directed to peptide isosteres: copper mediated reaction of trialkylaluminum with 4,4-difluoro-5-hydroxyallylic alcohol derivatives
Copper mediated alkyl-transfer reaction of trialkylaluminum (R3Al) with (E)-4,4-difluoro-5-hydroxyallylic alcohol derivative smoothly proceeded to give the corresponding 2-alkylated 4-fluoro-5-hydroxyhomoallylic alcohol derivative with completely Z and 2,5-syn selective manner. Regio- and stereoselective conversion of the C5-hydroxyl group of the fluoroolefin thus obtained to amino group could be achieved