Unusual β,β′-coupling and β-alkylation of methyl 2,3,3-trifluoropropenoate by lithium diorganocuprates

Methyl 2,3,3-trifluoroprop-2-enoate (1) reacts with lithium diorganocuprates in two ways, by fluorine substitution at C-3 with alkyl or aryl, or by β,β′ C,C-coupling. The reaction product was strongly dependent on the organyl structure: while dibutyl- or diphenylcuprate reacted by C-3 substitution, dimethylcuprate afforded the product of the coupling, dimethyl (Z,Z)-2,3,4,5-tetrafluorohexa-2,4-dienedioate (3). (Z)-Configuration is highly prevailing in 3-alkylated 2,3-difluoropropenoates (77–90% rel.).

Lithium dimethyl- or di(tert-butyl)cuprate afforded the product of unusual coupling, while dibutyl- or diphenylcuprate gave the product of β-fluorine substitution in the substrate.Figure optionsDownload as PowerPoint slideResearch highlights▶ We have found two ways for reactions of trifluoropropenoate with Li diorganocuprates. ▶ Recently, only β-substitution of fluorine was known. ▶ β C–C coupling occurs when LiCuMe2 or LiCu(tert-Bu)2 is applied. ▶ (Z)-Configuration is highly prevailing or complete in the products.