Microwave assisted synthesis of 2,3-diaryl-6,7-dihydro-5H-pyrrolo[1,2-a]imidazoles through direct condensation of aryl 1,2-diketones and l-proline under solvent-free condition

Microwave irradiation of a solid mixture of aryl 1,2-diketones, l-proline, and ammonium acetate (excess) for 15 min produces 2,3-diaryl-6,7-dihydro-5H-pyrrolo[1,2-a]imidazoles in moderate yields. Mechanistically this one-pot three-component reaction generates pyrroloimidazoles through the intramolecular cyclization of 1,2-diimine intermediates derived from the condensation of aryl 1,2-diketones, l-proline, and ammonia in 1:1:1 molar proportion. The significant advantages of this methodology are cost-effectiveness, operational simplicity, and reduced reaction time.