A 1H, 13C and 15N NMR spectroscopic and GIAO DFT study of ethyl 5-oxo-2-phenyl-4-(2-phenylhydrazono)-4,5-dihydro-1H-pyrrole-3-carboxylate

15N-Labelled ethyl 5-oxo-2-phenyl-4-(2-phenylhydrazono)-4,5-dihydro-1H-pyrrole-3-carboxylate was synthesized by azo-coupling of diazotized aniline (using Na15NO2 , 99% 15N) with ethyl 4,5-dihydro-5-oxo-2-phenyl-(1H)-pyrrole-3-carboxylate. The product was formed as a tautomeric hydrazone mixture as confirmed by 13C and 15N chemical shifts, and was obtained as a mixture of E and Z isomers according to nJ(15N, 13C). A comparison of the 1H NMR data with GIAO DFT calculations enabled determination of the configuration of the carboxy ester group in both isomers.