Synthesis and GIAO NMR calculations for some new 4,5‐dihydro‐1 H ‐1,2,4‐triazol‐5‐one derivatives: comparison of theoretical and experimental 1 H and 13 C chemical shifts

Four novel 3‐alkyl(aryl)‐4‐(4‐methoxycarbonylbenzylidenamino)‐4,5‐dihydro‐1 H ‐1,2,4‐triazol‐5‐ones ( 2 ) were synthesized by the reactions of 3‐alkyl(aryl)‐4‐amino‐4,5‐dihydro‐1 H ‐1,2,4‐triazol‐5‐ones ( 1 ) with methyl 4‐formylbenzoate and characterized by elemental analyses and IR, 1 H NMR, 13 C NMR and UV spectral data. In addition, isotropic 1 H and 13 C nuclear magnetic shielding constants of 2 were obtained by the gauge‐including‐atomic‐orbital (GIAO) method at the B3LYP density functional level. The geometry of each compound was optimized using the 6–311G basis set. Copyright © 2005 John Wiley & Sons, Ltd.