15N‐NMR‐Studien der Tautomerie in N‐monosubstituierten Amidinen und in N,N′‐Diphenylguanidin

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Abstract
15N NMR Studies of the Tautomeric Equilibrium of N‐Monosubstituted Amidines and of N,N′‐Diphenylguanidine15N NMR data are reported for tautomeric N‐monosubstituted amidines 1a and b and for N,N′‐diphenylguanidine (6). In order to elucidate the position of the tautomeric equilibrium, the nitrogen resonances of the salts of 1a, b and 6 were also determined. For comparison, chemical shifts δ15N were measured of non‐tautomeric amidines 2 – 5. The preferred tautomers for N‐phenylbenzamidine (1a) and for 6 have the CN double bond conjugated with the phenyl group. Replacement of an NH proton with an alkyl group, as in 1b, has little effect on the tautomeric equilibrium of amidines.