Alkylation of (Fluorocarbethoxymethylene)-tri-n-butylphosphorane: A Facile Entry to α-Fluoroalkanoates

Article abstract of DOI:10.1021/jo00295a016

(Fluorocarbethoxymethyl)trialkylphosphonium bromides 6, prepared from ethyl bromofluoroacetate and tertiary phosphines, react with n-butyllithium in THF to give the corresponding phosphoranes 7.Reaction of the pregenerated (fluorocarbethoxymethylene)tri-n-butylphosphorane 7a with primary alkyl iodides and activated alkyl bromides followed by in situ hydrolysis of the alkylated salts provides the fluoroalkanoates 9 in a one-pot reaction.In the case of secondary alkyl halides, no substitution was observed, the main reaction being decomposition of the phosphorane.However, the anion obtained from diisopropyl (fluorocarbethoxymethyl)phosphonate 10 b reacts with CH3CH(Ph)Br and (CH3)2CHI to afford the corresponding alkylated phosphonates in good yields.Displacement of the phosphonate moiety either by base-induced hydrolysis or by reduction was unsuccessful.