The spatial structure of various derivatives o fix, c~-diamino-~-cyano-B-nitroethylene has been investigated using IH and 13C NMR spectroscopy. It was shown that the configuration of the investigated push-pull enamines is determined by the possibility of creating an intramolecular hydrogen bond between NH and NO 2 groups or by stertc interactions. A series of 3,5-diamino-5-nitropyrazole derivatives has been synthesized by reacting these amines with hydrazine hydrate.In the previous communications of this series, the synthesis and some properties of push-pull enamines, derivatives of ct,c~-diamino-B-cyano-/3-nitroethylene, were described [1]. The latter are extremely interesting starting materials for the synthesis of various substituted heterocycles. However, the presence in their structure of a completely substituted ethylene fragment creates significant difficulties when investigating their configuration [2]. We note the indications in the literature that the configuration of compounds of this type has not been successfully determined previously [3]. The aim of the present work was to study the fine structure of the indicated enamines by NMR spectroscopy. The primary subject selected for investigation was c~-methylamino-(N,N-dimethylaminomethylene)amino-/3-cyano-B-nitroethylene (I).
I
Mc a ISignals were observed in the 1H NMR spectrum of this compound in DMSO-D 6 and DMF-D 7 (see Table 1) for the NH group proton as quartets at 9.82 (3JNH,M e = 3.9 Hz) and 9.96 ppm (3JNH,M e ----3.8 Hz) respectively. Taking the spectrum at reduced temperature in DMF-D 7 showed that the position of the signal remained practically unchanged 5NH -----10.08 at -30~ and 10.10 ppm at -40~ This indicates that a fairly stable intramolecular hydrogen bond (IMB) between the NO 2 and NH groups is a characteristic of compound (I) and determines its configuration unequivocally. Clarification of the conformational features of enamine (I) was carried out using the nuclear Overhauser effect (NOE). On irradiating the proton signal of the NMe group (of the NHMe fragment) at 2.92 ppm (DMSO-D6), an increase was observed in the intensity of the signals of the NH group protons (at 9.82 ppm) of 15% and of the =CH proton (8.11 ppm) of 5% which indicates the spatial proximity of the meso proton of the amidine fragment and the methyl group of the NHMe substituent. Assignment of the methyl *For Part 2, see [1]. *These compounds may also be considered as derivatives of acrylonitrile.
According to 1 Н and 13 С NMR data, enamines of 3 formyl 4 hydroxycoumarin exist in the keto enamine tautomeric form and undergo Z/E isomerization around the C=C bond in CDCl 3 , DMSO d 6 , and CD 3 OD at room temperature. The activation energies of Е/Z isomer ization were measured experimentally and calculated by the B3LYP/6 311++G(d,p) method. An X ray diffraction study showed that 3 (benzyliminomethyl)chromane 2,4 dione in the crystalline state exists as a mixture of two keto enamine isomers.
Сondensation of indolin 2 one (oxindole) lactim ether with malononitrile leads to 2 diсyanоmethylidene 2,3 dihydroindole, the reaсtion of whiсh with dimethylformamide diethyl aсetal (or with triethyl orthoformate) and the subsequent сyсlization afford 4 сyanоpyrido[4,3 b]indoles (γ сarbоlines). 3 Amino 4 сyanоpyrido [4,3 b]indole was used in the synthesis of substi tuted pyrimido[4,5 c] γ сarbоlines.
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