Reductive Dimerization of Alkylidenemalonates Using Samarium(II) Diiodide and 1H-NMR Behavior of the Dimers, 2,3-Diaryl-1,1,4,4-butaneteracarboxylates.
Alkylidenemalonates were readily dimerized in the presence of SmI2 to give 2,3-disubstituted 1,1,4,4-butanetetracarboxylates as mixtures of meso and racemic isomers in moderate to good yields. The structure of the less polar isomer of tetraethyl 2,3-diphenyl-1,1,4,4-butanetetracarboxylate was determined by X-ray crystallographic analysis to be the meso form. Characteristic 1H-NMR behavior of the meso