An Efficient Synthesis of 1,2,4-Trisubstituted Imidazoles from Arylacetic Acids and N -Arylbenzamidines via Simultaneous C-H and N-H Bond Activation

A convenient and effective FeCl3 catalyzed one-pot three component protocol for the synthesis of 1,2,4-trisubstituted imidazoles from arylacetic acids, N-arylbenzamidines and nitromethane via simultaneous CH and NH bond activation has been developed. The reaction involves CH activation of arylacetic acid to form aromatic aldehyde which on condensation with N-arylbenzamidine gives azadiene. Nitromethane on Michael addition with azadiene produces ring annulated intermediate which upon subsequent cyclization-elimination sequence offers imidazole. The process utilizes readily available arylacetic acids and inexpensive catalyst. This user friendly protocol provided 1,2,4-trisubstituted imidazoles in moderate to good yields with high functional group tolerance and ample substrate scope.