Spectral characterization and crystal structure of some 2,6-diarylthian-4-one hydrazone derivatives

A series of cis and trans 2,6-diarylthian-4-one hydrazone derivatives (11–16) have been synthesized and characterized by 1H, 13C and two dimensional NMR spectroscopy. For the 2r,6t-diphenylthian-4-one N-isonicotinoylhydrazone (14) X-ray diffraction have also been recorded. The coupling constants suggested that the cis-hydrazones (11–13), which have the phenyl groups in cis orientation, largely exist in chair conformations with equatorial orientation of the phenyl groups 11C. Analysis of the vicinal coupling constants of trans-hydrazones (14–16) suggests that boat forms 14B must make significant contributions to it and the relative population is 58%. Moreover, in solution chair conformations 14C and 14C′, may contribute to 14. The NOESY and X-ray diffraction of 14 gives definite evidence for the contribution of 14C.