Metal-Controlled Switchable Regioselective Synthesis of Substituted Imidazoles and Pyrroles via Ring Opening/Cyclocondensation with 2H-Azirines

Catalytic selective annulation of 2H-azirinesconstitutes a general and modular strategy for the generation of molecularcomplexity. By using Pd-catalyzed ring opening/heterocyclization associatedwith direct cleavage of C-N and C-C bonds under appropriateconditions, the formation of imidazoles is presented. Alternatively,the silver-catalyzed radical [3 + 2] cycloannulation of 2H-azirines and 1,3-dicarbonyl compounds provides highly functionalizedpyrrole derivatives. Both aliphatic cyclic and acyclic diketones aretolerated with good regioselectivity. Moreover, a radical captureexperiment was carried out to determine the proposed mechanism, providingsupport for a facile radical process.

Automated summary

The catalytic selective annulation of 2H-azirines provides a general and modular strategy for generating molecular complexity. It involves Pd-catalyzed ring opening/heterocyclization and direct cleavage of C-N and C-C bonds to form imidazoles. Alternatively, a silver-catalyzed radical [3 + 2] cycloannulation of 2H-azirines and 1,3-dicarbonyl compounds produces highly functionalized pyrrole derivatives.