Crystal structure, Hirshfeld surface analysis and energy framework study of 6-formyl-7,8,9,11-tetra-hydro-5H-pyrido[2,1-b]quinazolin-11-one.

At 100 K, the title compound, C13H12N2O2, crystallizes in the ortho-rhom-bic space group Pna21 with two very similar mol-ecules in the asymmetric unit. An intra-molecular N-H⋯O hydrogen bond leads to an S(6) graph-set motif in each of the mol-ecules. Inter-molecular π-π stacking and C=O⋯π inter-actions involving the aldehyde O atoms link mol-ecules into stacks parallel to [100]. A Hirshfeld surface analysis indicates that the most important contributions to the crystal packing stem from H⋯H (49.4%) and H⋯O/O⋯H (21.5%) inter-actions. Energy framework calculations reveal a significant contribution of dispersion energy. The crystal studied was refined as a two-component inversion twin.

Stereochemistry of the methyl-idene-bridged quinazoline-iso-quinoline alkaloid 3-{[6,7-dimeth-oxy-1-(4-nitro-phen-yl)-1,2,3,4-tetra-hydro-isoquinolin-2-yl]methyl-idene}-1,2,3,9-tetra-hydro-pyrrolo-[2,1-b]quinazolin-9-one methanol monosolvate.

Two potentially bioactive fragments, namely a tricyclic quinazoline derivative with an exocyclic alkene moiety and a substituted iso-quinoline, are coupled to give 3-{[6,7-dimeth-oxy-1-(4-nitro-phen-yl)-1,2,3,4-tetra-hydro-isoquinolin-2-yl]methyl-idene}-1,2,3,9-tetra-hydro-pyrrolo-[2,1-b]quinazolin-9-one. The target product crystallizes as a methanol solvate, C29H26N4O5·CH4O, and is E configured. The alternative Z isomer would necessarily imply either considerable twist about the central double bond or very unfavourable intra-molecular contacts between sterically more demanding substituents. The main residue and the co-crystallized solvent mol-ecule aggregate to discrete pairs via a classical O-H⋯O hydrogen bond with a distance of 2.8581 (7) Šbetween the methanol OH donor and the quinazolinone O=C acceptor.

(E)-6-(Furan-2-yl-methyl-idene)-6,7,8,9-tetra-hydro-pyrido[2,1-b]quinazoline-11-thione.

A quinazolinthione, C17H14N2OS, was synthesized by the condensation reaction of 6,7,8,9-tetra-hydro-11H-pyrido[2,1-b]quinazolin-11-thione with furfural. The mol-ecule crystallizes in the monoclinic system (Cc space group) and has an E configuration with respect to the exocyclic C=C bond. In the crystal, mol-ecules are linked through C-H⋯π(furan) inter-actions, forming zigzag chains propagating along the [001] direction.

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.

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 (1)H-NMR spectroscopy and in the crystal form by X-ray analysis. Molecule 1 crystallized in a primitive monoclinic cell, space group capital ER, P2(1/c). The cell dimensions are a=7.970(6) A, b=7.061(2) A, c=20.537(7) A, beta=97.69(5) degrees , V=1145.3(10) A(3). Molecule 2 crystallized in a triclinic cell, space group P-1, the cell dimensions are a=8.196(5) A, b=8.997(6) A, c=9.435(4) A, alpha=74.22(4) degrees, beta=89.75(4) degrees , gamma=74.07(5) degrees , V=641.9(6) A(3). In both compounds the presence of intra-molecular 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, (1)H-NMR and X-ray methods.