DOI:10.1002/jhet.4235

A theoretical study of inversion barriers and NMR chemical shifts of 3‐pyrazolines (2,3‐dihydro‐1H‐pyrazoles)

A rather neglected family of heterocyclic compounds, the 3‐pyrazolines or 2,3‐dihydro‐1H‐pyrazoles, has been studied theoretically at the B3LYP/6–311++G(d,p) level to obtain geometries and energies and at the GIAO/B3LYP/6–311++G(d,p) level for NMR chemical shifts. The calculated barriers of inversion of the N‐substituents reproduce adequately the scarce experimental data. The calculated ¹H and ¹³C chemical shifts are consistent with those reported in the literature. A combination of both results, geometries, and ¹³C chemical shifts, shed light on the conformation of N‐phenyl groups.