Samarium reagent-promoted formation of benzoins from diarylmethanones and DMF via a carbene rearrangement reaction

Prompted by samarium metal in DMF with TMSCl or iodine as an activator, or by SmI2/THF system, diarylmethanones react readily with DMF to afford benzoins in moderate to good yields via rearrangement of aryl groups. As for asymmetric diarylmethanones, products resulting from the migration of either aryl group were obtained, where the migration of aryl groups shows certain priority.