Selective Synthesis of Acylated Cross-Benzoins from Acylals and Aldehydes via -Heterocyclic Carbene Catalysis.

The utility of acylals as building blocks for selective cross-benzoin synthesis was explored in this study. The synthesis of α-acetoxyketones (-acyl cross-benzoins) was achieved via selective -heterocyclic carbene-catalyzed cross-benzoin reactions using acylals as aldehyde equivalents. Thus, the combination of -substituted phenyl acylals and aromatic/aliphatic aldehydes as coupling substrates using bicyclic triazolium salts as precatalysts and potassium carbonate as a base in THF at reflux temperature selectively yielded -acyl cross-benzoins.