A controllable synthesis of trisubstituted imidazoles and pyrroles has been developed through rhodium(II)-catalyzed regioselective annulation of N-sulfonyl-1,2,3-trizaoles with β-enaminones. The imidazole ring was formed through 1,1-insertion of N-H bond to α-imino rhodium carbene and subsequential intramolecular 1,4-conjugate addition when α-carbon atom of amino group bearing with methyl, whereas utilizing phenyl substituent constructed pyrrole ring via intramolecular nucleophilic addition. Features such as mild conditions, good functional groups tolerance, gram-scale synthesis, and valuable transformations of the products qualified this unique protocol as an efficient tool for the synthesis of N-heterocycles.

The three-component reaction of enaminones, benzaldehyde and hydrazine-HCl or four-component reaction of enaminones, benzaldehyde, hydrazine–HCl and ethyl cyanoacetate in water in the presence of catalytic amount of ammonium acetate has been devised as a straightforward , sustainable approach for the synthesis of 1-H-pyrazole, N-aminopyridine and pyrazol[3,4-b]pyridine derivatives . The key benefits of this approach is simple experimental procedure associated with cost effective and environmentally friendly techniques.