TABLE 3. Spectral Characteristics of Compounds 2a-e, 3b,c
Com-
pound
1Н NMR spectrum, δ, ppm (J, Hz)
2a
2b
1.91 (2H, q, J = 6.8, CH2CH2CO); 2.15 (2H, t, J = 6.8, CH2CO);
3.97 (2Н, t, J = 7.2, СН2N); 6.89 (1Н, s, Н-4 imidaz.); 7.16 (1Н, s, Н-5 imidaz.);
7.62 (1Н, s, Н-2 imidaz.); 9.5 (1Н, br. s, COOН)
1.99 (2H, q, J = 7.0, CH2CH2CO); 2.21 (2H, t, J = 6.4, CH2CO);
4.20 (2Н, t, J = 7.0, СН2N); 7.96 (1Н, s, Н-3 triaz.); 8.50 (1Н, s, Н-5 triaz.);
12.21 (1Н, br. s, COOН)
2c
1.98 (2H, q, J = 7.5, CH2CH2CO); 2.20 (2H, t, J = 7.5, CH2CO);
4.05 (2Н, t, J = 7.0, СН2N); 8.54 (2Н, s, Н-3,5 triaz.); 12.25 (1Н, br. s, COOН)
2d*
2.02 (2H, q, J = 7.0, CH2CH2CO); 2.23 (2H, t, J = 7.0, CH2CO);
4.26 (2Н, t, J = 7.0, СН2N); 7.12-7.35 (2H, m, Н-5,6, benzimidaz.);
7.63 (2H, t, Н-4,7, benzimidaz., J = 8.7); 8.21 (1Н, s, Н-2 benzimidaz.);
12.22 (1Н, br. s, COOН)
2e
3b
3c
1.75 (2H, q, J = 7.3, CH2CH2CO); 2.26 (2H, t, J = 6.9, CH2CO);
4.18 (2Н, t, J = 7.7, СН2N); 4.31 (2Н, s, CH2Ph); 7.12-7.26 (3Н, m, 3СН arom.);
7.27-7.40 (4Н, m, 2CH arom., 2СН benzimidaz.); 7.48-7.67 (2Н, m, Н-4,7, benzimidaz.)
1.19 (3Н, t, J = 7.4 CH3CH2O); 2.15 (2H, q, J = 7.4, CH2CH2CO); 2.25 (2H, t, J = 6.6, CH2CO);
4.07 (2Н, q, J = 7.4, СН2О); 4.20 (2Н, t, J = 6.6, СН2N); 7.88 (1Н, s, Н-3 triaz.);
8.00 (1Н, s, Н-5 triaz.)
1.26 (3Н, t, J = 7.4, CH3CH2O); 2.15 (2H, q, J = 6.6, CH2CH2CO);
2.33 (2H, t, J = 6.6, CH2CO); 4.13 (2Н, q, J = 7.4, СН2О);
4.23 (2Н, t, J = 6.6, СН2N); 8.16 (2Н, s, Н-3,5 triaz.)
_______
* imidaz. – imidazole, triaz. – triazole, benzimid. – benzimidazole.
In the IR spectra of the obtained azolylbutyric acids 2a-e an absorption band for the carbonyl group is
observed at 1680-1712 cm-1, and for the hydroxyl at 3390-3410 cm-1. On analyzing the NMR spectra of the
isomeric acids 2b and 2c it should be mentioned that the triazole methine proton of the 4-substituted product is
displayed as a singlet at 8.54 ppm of double intensity, like the C(5)H methine proton (8.50 ppm) of acid 2b,
analogously located between nitrogen atoms of pyridine and pyrrole types. In the 13C NMR spectrum the signal
of the methylene group bonded to the azole of the isomeric butyric acids 2b and 2c is observed at lower field
(47.38 ppm) for the 1-substituted product in comparison with acid 2c (43.64 ppm). Data of elemental analysis
and NMR and IR spectroscopy given in EXPERIMENTAL confirm the structure of the compounds obtained.
With the aim of determining the applicability of the quantum-chemical method for predicting the
direction of the interaction of azoles with γ-butyrolactone leading to products of N-alkylation or N-acylation,
quantum-chemical calculations were carried out of the energy characteristics (∆Hf, Etotal). The calculations were
carried out by the semiempirical PM3 method with the HyperChem 6.03 set of programs [15] with complete
optimization of the geometry of the molecules. For the determination of ∆H of a reaction this method is most
applicable since the heat of formation is a parameterizable property [14]. A more precise calculation of the
structures of the compounds was carried out by the Hartree-Fock method on the 6-31G* basis. For molecules
with closed electron shells the formalism of the restricted Hartree-Fock (RHF) method was used. The
calculations of anions were carried out with the unrestricted Hartree-Fock (UHF) method.
The calculations showed that on interacting γ-butyrolactone with neutral azoles alkylation was more
favourable than acylation, although on the whole the values of ∆Hp did not exceed 30 kJ/mol. Consequently
under similar conditions products of acylation of azoles, imidazolides of 4-hydroxybutyric acids, were obtained
and isolated together with 4-(imidazol-1-yl)butyric acids by the authors of [7]. Starting from the calculated
charges on the C(2) and C(5) atoms of the lactone (q2 = 0.787, q5 = 0.004) the product of N-acylation is the
product of kinetic control, since the nucleophilic opening of the lactone ring occurs probably as a result of attack
at the most electropositive atom C(2) of the lactone. On subsequent heating the most stable product of
772