Double addition of azoles to glyoxal: characterization of the bis-adducts and theoretical study of their structure
We have studied the structure (isomerism and conformation) of the products resulting from the double addition of four NH-azoles, benzotriazole, pyrazole, imidazole and benzimidazole, on glyoxal and on DODO ([1,4]-dioxane-2,3-diol). The reactions result in the formation of meso and d,l diastereoisomers, although in all cases a significant amount of unreacted azole remains. The four component mixtures were analyzed by 1H and 13C NMR. DFT calculations (B3LYP/6-31G*) were carried out to determine the relative stabilities of the different structures.