Methylsulfinyl (Dimsyl) anion as umpolung catalyst for the chemoselective cross-benzoin reaction of α-diketones with aldehydes

Article abstract of DOI:10.1002/adsc.201300652

The hitherto unreported ability of the methylsulfinyl carbanion (dimsyl anion) to generate acyl anion equivalents is described. The dimsyl anion, in fact, efficiently catalyzes chemoselective intermolecular cross-benzoin condensations of diaryl α-diketones (benzils) with various aromatic and aliphatic aldehydes to give the corresponding aryl-aryl and aryl-alkyl benzoin benzoates in an atom-economic fashion. The dimsyl anion acts as an environmentally friendly alternative to the toxic cyanide anion and it is obtained by in situ deprotonation of dimethyl sulfoxide (DMSO) solvent with a catalytic amount of a strong base, potassium tert-butoxide (t-BuOK) the optimal promoter. The assumption that the methylsulfinyl carbanion is the active catalyst in the title transformation is supported by electrospray ionization mass spectrometry (ESI-MS) experiments. Copyright