GIAO DFT 13C/15N chemical shifts in regioisomeric structure determination of fused pyrazoles

The combined use of two-dimensional NMR correlation experiments and gauge including atomic orbital density functional theory in 13C NMR chemical shift (CS) calculations allowed reliable and simple structural determination of regioisomeric heterocyclic systems that originate from the reactions of acylquinolinones with substituted hydrazines. Moreover, the results of differential analysis between the calculated 15N NMR CSs for hypothetical structures and the experimental data of the title azaheterocyclic systems were even more advantageous with respect to 13C because there was no need for correlational analysis: structures of the regioisomeric compounds could be determined just by direct comparison.