Synthesis, Tautomeric States and Crystal Structure of (Z)-Ethyl 2-Cyano-2-(3H-Quinazoline-4-ylidene) Acetate and (Z)-Ethyl 2-Cyano-2-(2-Methyl-3H-Quinazoline-4-ylidene) Acetate

Abstract

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.

A modular approach for the installation of functionalized phosphonates to heterocycles

“…The increased acidity of the remaining -proton and stabilization from hydrogen bonding interactions between the N-H and P=O resulted in isolation of a tautomeric form of the SNAr product 25, which was unambiguously determined by single crystal X-ray crystallography. 39 Phosphonates bearing benzylic substituents all performed exceptionally well (31)(32)(33)(34)(35) and provide intermediates capable of downstream modifications (e.g. reduction of NO2 or cross-couplings with sp 2 -halides).…”

2-(Isopropylidenehydrazono)-3-methyl-2,3-dihydroquinazolin-4(1H)-one

“…For related literature, see: Djinović et al (1990); Rewcastle et al (1995); Seijas et al (2000); Rajnikant et al (2001); Tulyasheva et al (2005); Naveen et al (2006). Mo K radiation = 0.09 mm À1 T = 293 (2) K 0.50 Â 0.35 Â 0.25 mm Table 1 Hydrogen-bond geometry (Å , ).…”

Experimental and theoretical investigation of the electronic absorption spectra of 2-H(methyl, methylthio, phenyl)-3,4-dihydro-4-quinazolinylidenecyanoacetic ester

“…The synthesis and investigation of the tautomerism of derivatives of 2-H(methyl)-3,4-dihydro-4-quinazolinylidenecyanoacetic ester by X-ray structural analysis and 1 H NMR spectroscopy was reported previously [4]. The data of 1 H NMR spectra showed the presence of an intramolecular hydrogen bond (IMHB) between the hydrogen atoms at the N (3) atom and the carbonyl group of the ester residue.…”

“…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] Since it seemed of interest to investigate the effect of the nature of a substituent in position 2 on the IR and UV spectral characteristics of derivatives of molecule 1, we have carried out an experimental and theoretical investigation of the electronic absorption spectra of compounds 1-4.…”

“…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]. …”