Catalytic selective annulation of 2H-azirines
constitutes a general and modular strategy for the generation of molecular
complexity. By using Pd-catalyzed ring opening/heterocyclization associated
with direct cleavage of C–N and C–C bonds under appropriate
conditions, the formation of imidazoles is presented. Alternatively,
the silver-catalyzed radical [3 + 2] cycloannulation of 2H-azirines and 1,3-dicarbonyl compounds provides highly functionalized
pyrrole derivatives. Both aliphatic cyclic and acyclic diketones are
tolerated with good regioselectivity. Moreover, a radical capture
experiment was carried out to determine the proposed mechanism, providing
support for a facile radical process.