A Route to Head-to-Head Trimers of Acrylic Acid Derivatives by Reductive Coupling of Ethyl Cinnamate-Based Vinyl Triflates.

A transition metal-free reductive coupling reaction between ethyl cinnamates-based vinyl triflates and methyl acrylate in 1,3-dimethyl-2-imidazolidinone (DMI) enabled C-C bond formation at the sp2 carbon atom, affording 3-aryl-hex-2-enedioic acid esters with broad substrate scope and good yields under very mild reaction conditions. The successive reductive coupling reactions of the α,β-unsaturated ester structure with methyl acrylate in N,N-dimethylformamide (DMF) led to the formation of head-to-head trimers of acrylic acid esters in good yields. Other electrophiles such as chlorotrimethylsilane, aliphatic aldehydes, and acetic anhydride could be used instead of methyl acrylate to afford a variety of 3-aryladipic acid esters bearing quaternary carbon centers at the 3-position.