Rhodium-catalyzed cyclopropanation using ene-yne-imino ether compounds as precursors of (2-pyrrolyl)carbenoids.

[reaction: see text] The reaction of alkenes with conjugated ene-yne-imino ether or ene-yne-aldimine in the presence of a catalytic amount of Rh(OAc)(2) gives (2-pyrrolyl)cyclopropanes in good yields. The key intermediate of this cyclopropanation is a (2-pyrrolyl)carbenoid generated by the nucleophilic attack of imine nitrogen atom at an internal alkyne carbon activated by rhodium complex. The intramolecular reaction also proceeds to afford a polycyclic pyrrole.