A new mode of carbene‐catalyzed heteroatom activation and asymmetric reactions is disclosed. The reaction starts with addition of a carbene catalyst to a (benz)imidazole‐derived aldimine substrate. Subsequent oxidation and proton transfer lead to ...
A new mode of carbene‐catalyzed heteroatom activation and asymmetric reactions is disclosed. The reaction starts with addition of a carbene catalyst to a (benz)imidazole‐derived aldimine substrate. Subsequent oxidation and proton transfer lead to the formation of a catalyst‐bound triaza‐diene as the key intermediate, in which the nitrogen atom at a site remote to the catalyst‐substrate bond is activated. This unusual triaza‐diene intermediate then undergoes highly enantioselective reactions with activated ketones through a concerted asynchronous pathway, as supported by mechanistic studies and preliminary density function theory calculation.
A new mode of carbene‐catalyzed activation and reaction of nitrogen atom is disclosed. The reaction starts with the addition of the carbene catalyst to imine to form an aza‐Breslow intermediate to eventually form NHC‐bound triaza‐diene as the key intermediate. This triaza‐diene intermediate then undergoes highly enantioselective reactions with activated ketones through a concerted asynchronous pathway.