Studies on nitroenamines. Part III. Synthesis and spectral properties of 4‐Acyl‐1‐arylimidazoles

The catalytic (C/Pd) hydrogenation of 3‐arylamino‐2‐nitro‐2‐enones (1) in the presence of carboxylic ortho esters (2) affords 4‐acyl‐1‐arylimidazoles (3) in yields (20–70%) which depend on the degree of substitution of the imidazole ring. The spectral properties of compounds 3, and particularly the 13C‐nmr spectra, reflect both the electronic and steric effects of the substituents on the π‐electron delocalization and planarity of the bicyclic system.