Kumada Arylation of Secondary Amides Enabled by Chromium Catalysis for Unsymmetric Ketone Synthesis under Mild Conditions

The synthesis of aromatic ketones by chromium-catalyzed Kumada arylation of secondary amides with organomagnesium reagents is described. This reaction was enabled by using low-cost chromium(III) salt as a precatalyst, combined with trimethylsilyl chloride as an additive, and presents a rare example of catalytic transformation of secondary amides to ketones at room temperature. It was shown that catalytically active low-valent chromium species might be responsible for the amide–ketone exchange by mechanism involving the activation of benzimidate intermediate.