Reaction of symmetrical and unsymmetrical (thio)barbituric acids with aldehydes in the presence of triethylamine afforded a new form of bis-(thio)barbiturate containing charge-separated inter- and eight-membered intramolecular H-bonds. The reaction products were obtained as bis-(thio)barbiturates containing eight-membered intramolecular H-bond in the presence of l-(+)-tartaric acid (TA). The intramolecular H-bond strength (kcal/mol) and corresponding pKa value for 4ab′ were estimated to be 37 kcal/mol and −1.3, respectively.
在
三乙胺存在下,对称和不对称(
硫代)
巴比妥酸与醛反应生成了一种新形式的双-(
硫代)
巴比妥酸,其中含有电荷分离的分子间和八元分子内 H 键。在 l-(+)-
酒石酸(TA)存在下,反应产物为含有八元分子内 H 键的双-(
硫代)
巴比妥酸酯。据估计,4ab′的分子内 H 键强度(kcal/mol)和相应的 pKa 值分别为 37 kcal/mol 和-1.3。