Synthesis and Characterization of Dihydrazide Derivatives Containing Benzimidazole Ring

Ten novel dihydrazide derivatives containing benzimidazole ring (7a similar to 7j) were synthesized by (un)substituted phenol and chloroacetic acid as starting materials via a series of reactions. The structure of representative compound 7c was confirmed by H-1 NMR, C-13 NMR, 2D NMR (H-1-H-1 COSY, HSQC, HMBC and NOESY) and variable-temperature H-1 NMR spectra. The experimental results indicate that compound 7c in DMSO at room temperature exists in the tautomeric A and B isomers, and A isomer is dominant (87.65%). On the basis of the analytic results of compound 7c, H-1 NMR spectra of other target compounds were also assigned and the content of dominant A isomer is in the range of 80.55%similar to 89.90%.