13C NMR spectra of p-nitrobenzoyl 2-, 4-, and 6-aminopyridine-3-carboxylates, their hydrochlorides, trifluoroacetates and 1-benzyl derivatives were studied. As found from the chemical shifts of pyridine carbon atoms C-2, C-4 and C-6, the free bases exist in the amino form whereas hydrochlorides and 1-substituted pyridinium derivatives in the imino form. Trifluoroacetates of the 2- and 6-amino derivatives have structure similar to that of amidiniumcarboxylates (parallel hydrogen bonds and partially ionic character) whereas trifluoroacetate of the 4-amino derivative is structurally close to the corresponding hydrochloride. The found structures were confirmed by 1H NMR and IR spectroscopy.
研究了对
硝基苯甲酰基2-, 4-和6-
氨基吡啶-3-
羧酸酯、它们的盐酸盐、
三氟乙酸盐和1-苄基衍
生物的
13C NMR光谱。从
吡啶碳原子C-2、C-4和C-6的
化学位移中发现,自由碱存在于
氨基形式,而盐酸盐和1-取代
吡啶衍生物存在于
亚胺形式。2-和6-
氨基衍
生物的
三氟乙酸盐具有类似于酰胺盐(平行氢键和部分离子性)的结构,而4-
氨基衍
生物的
三氟乙酸盐在结构上接近于相应的盐酸盐。通过
1H NMR和IR光谱证实了发现的结构。