Access to pyrrole-based heterocyclic compounds via addition of pyrrole to C=C and C=N bonds

A series of metal triflate-catalyzed addition reactions of pyrrole to C=C and C=N bonds have been investigated to access pyrrole-based heterocyclic compounds. The addition of pyrrole to different α,β-unsaturated compounds or N-tosyl imines afforded suitable structures for the construction of [5-5] bicyclic systems or porphyrins, respectively. Intramolecular cyclization reactions were applied for the synthesis of pyrrolizine derivatives. In the other reaction mode, intermolecular cyclization reactions gave A₄- and trans-A₂B₂-meso-substituted porphyrins under mild reaction conditions with low scrambling.