AMIDINES .7. H-1 AND C-13 NUCLEAR MAGNETIC-RESONANCE STUDIES ON TAUTOMERISM, GEOMETRICAL ISOMERISM, AND CONFORMATION OF SOME CYCLIC AMIDINES, GUANIDINES, AND RELATED SYSTEMS
AMIDINES .7. H-1 AND C-13 NUCLEAR MAGNETIC-RESONANCE STUDIES ON TAUTOMERISM, GEOMETRICAL ISOMERISM, AND CONFORMATION OF SOME CYCLIC AMIDINES, GUANIDINES, AND RELATED SYSTEMS
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DOI：
10.1021/ja00843a033
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发表时间：
1975-01-01
影响因子：
15
通讯作者：
JEN, T
中科院分区：
文献类型：
--
作者：
JACKMAN, LM;JEN, T
本文发展了一种用~（13）H和~（13）C NMR化学位移明确测定许多已知的芳基环脒、胍、2-氨基咪唑、2-亚氨基（氨基）噻嗪及相关互变异构体系的主要互变异构形式的通用方法。在2-aryliminopyrrolidines的情况下，几何异构的证据被发现在这两个和13 C NMR实验。这些结果支持了以下结论：在所有这些潜在的互变异构体系中，主要的互变异构体是亚氨基形式[ArN= C（NHR）R ']而不是氨基形式[ArNHC（= NR）R']。这些化合物的结构在文献中通常被认为是主要的互变异构体，没有支持的证据，一般来说，很难区分这两种互变异构体。环脒（1）的互变异构现象已被广泛研究。6在这些体系中，亚氨基互变异构体（Ib）
A general method is developed using* H and 13C NMR chemical shifts to determine unambiguously the predomi-nant tautomeric form of many known aryl cyclic amidinesand guanidines, 2-aminoimidazoles, 2-imino (amino) thiazines, and related tautomeric systems. In the case of 2-aryliminopyrrolidines, evidence for geometrical isomerism was found in both and 13C NMR experiments. These results support the conclusion that, in all these potentially tautomeric systems under the present studies, the predominant tautomer is in the imino form [ArN= C (NHR) R'] rather than the amino form [ArNHC (= NR) R'].Many compounds containing an amidine moiety4 are known to possess interesting biological properties, particu-larly as antihypertensive agents. 5 Structures of these com-pounds have usually been presented in the literature as a presumed, predominant tautomer without supporting evidence and, in general, distinction between the two tautom-ers is difficult. Tautomerism in cyclic amidines (1) has been extensively studied. 6 In these systems, the problem is fur-ther complicated by the fact that the imino tautomer (lb)