The new compounds (Z)-ethyl 2-cyano-2-(3H- and 2-methyl-3H-quinazoline- 4-ylidene) acetate (1 and 2, respectively) were synthesized by multi-step reactions. The structures in a solution have been determined by 1H-NMR spectroscopy and in the crystal form by X-ray analysis. Molecule 1 crystallized in a primitive monoclinic cell, space group Р21/c. The cell dimensions are a=7.970(6) Å, b=7.061(2) Å, c=20.537(7) Å, β=97.69(5)°, V=1145.3(10) Å3. Molecule 2 crystallized in a triclinic cell, space group P1, the cell dimensions are a=8.196(5) Å, b=8.997(6) Å, c=9.435(4) Å, α=74.22(4)°, β=89.75(4)°, γ=74.07(5)°, V=641.9(6) Å3. In both compounds the presence of intramolecular NH---O=C hydrogen bonding between the nitrogen atom in position 3 of the quinazoline ring and a carbonyl group of the ethyl cyanoacetate residue was proven by quantum-chemical, 1H-NMR and X-ray methods.
The effect of substituents (Me, SMe, Ph) in position 2 has been studied on the nature of the absorption bands of 2-H-3,4-dihydro-4-quinazolinylidenecyanoacetic esters and a very high sensitivity on the substituent has been detected for the short wave maxima. On the basis of data calculated by the ZINDO/S method the featureless long-wave absorption band was assigned to an electronic transition from HOMO to LUMO caused by charge transfer from fragments of the benzene ring and the N=C-N bond to the >C=C-C=O fragment.Keywords: 2-substituted 4-quinazolinylidenecyanoacetic esters, quantum-chemical calculations, UV spectra.Quinazoline derivatives are of considerable interest in connection with their photochemical and biological properties [1-3]. 2-H-3,4-Dihydro-4-quinazolinylidenecyanoacetic ester (1) and its 2-methyl, methylthio, and phenyl derivatives 2-4 may also prove to be promising substances in this direction due to their planar structure (except for the ethyl group of the ester fragment) and the presence of conjugation between the quinazoline ring and the fragments of the cyanoacetate residue, and also the phenyl substituent in the case of compound 4. This leads to a significant change of electron density in molecules 1-4 in comparison with the separate fragments. In addition, from a theoretical point of view, these compounds are extremely interesting quinazoline derivatives due to the presence of several possible tautomeric forms [4].
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