Reduction-Olefination of Esters: A New and Efficient Synthesis of α-Fluoro α,β-Unsaturated Esters

Article abstract of DOI:10.1021/jo00302a030

A reduction-olefination sequence has been used to convert esters to α-fluoro α,β-unsaturated esters.In the presence of diisobutylaluminum hydride, esters are reduced to aldehydes that react in situ with <(EtO)2P(O)CFC(O)Et>^-Li⁺ to form the title compounds in good yield with high stereoselectivity.The reaction is applicable to aliphatic, aromatic, cyclic, unsaturated, perfluorinated, and partially fluorinated esters.The E/Z ratio of unsaturated esters formed in the reaction varies with the cations present in the reaction mixture.Solvents have very little influence on stereochemistry.The sequential transformation of PhC(O)OBuⁿ to (E)-PhCH=CFC(O)OEt and then to (E,E)-PhCH=CFCH=CFC(O)OEt illustrates the scope of this methodology, which introduces a fluorine atom adjacent to an ester functionality with concomitant elongation of the chain by two carbon atoms.