In the title mol­ecule, C11H11ClN2O, the pyrido[1,2-a]pyrimidine ring system is planar (maximum deviation = 0.0148 A) and the methyl C and carbonyl O atoms are nearly coplanar to it. The chloro­ethyl side chain is in a synclinal conformation, nearly orthogonal to the pyrimidine ring, with a dihedral angle between the chloro­ethyl side chain and the pyrimidine ring of 88.5 (1)°. Weak inter­molecular C—H⋯N and C—H⋯Cl hydrogen bonds along with π–π inter­actions between the pyrimidine and pyridine rings [centroid–centroid distance is 3.538 (2) A] form a three-dimensional network. The crystal is a racemic twin with a 0.68 (12):0.32 (12) domain ratio. MOPAC AM1 and density functional theory (DFT) theoretical calculations at the B3-LYP/6–311+G(d,p) level support these observations.

https://journals.iucr.org/e/issues/2009/08/00/ci2827/ci2827.pdf

3-(2-Chloro-ethyl)-2-methyl-4H-pyrido[1,2-a]pyrimidin-4-one.

In the title compound, C21H19N3O3S, the 5,6,7,8-tetra­hydro­pyridine ring adopts a half-chair conformation. The fused-thieno[2,3-d]pyrimidine ring system is essentially planar (r.m.s. deviation = 0.001 A) and forms a dihedral angle of 2.66 (6)° with the attached phenyl ring. The three-dimensional crystal packing is stabilized by C—H⋯O and C—H⋯N hydrogen bonds and C—H⋯π inter­actions.

https://journals.iucr.org/e/issues/2015/11/00/tk5390/tk5390.pdf

Crystal structure of ethyl 2-phenyl-4-(prop-2-yn-1-yl-oxy)-5,6,7,8-tetra-hydro-pyrido[4',3':4,5]thieno[2,3-d]pyrimidine-7-carboxyl-ate.

The asymmetric unit of the title compound, C23H23ClN4OS, contains two crystallographically independent mol­ecules in which the orientations of the propyl­amine group and chloro­phenyl rings with respect to the fused ring system are different. The terminal cyclo­hexene ring adopts a half-chair conformation. The crystal packing is stabilized by N—H⋯O, N—H⋯N and C—H⋯O hydrogen bonds and π–π inter­actions.

3‐(4‐Chloro­phen­yl)‐5‐methyl‐2‐propyl­amino‐8,9,10,11‐tetra­hydro‐2‐benzothieno­[2′,3′;2,3]­pyrido[4,5‐d]pyrimidin‐4(3H)‐one

In the title compound, C25H26N4O2S, the central tricyclic system is essentially planar. The crystal stacking is governed mainly due to π–π inter­actions.

5‐Methyl‐2‐morpholino‐3‐p‐tolyl‐8,9,10,11‐tetra­hydro‐2‐benzothieno[2′,3′:6,5]pyrido[4,3‐d]pyrimidin‐4(3H)‐one

In the title compound, C27H23N4O4S, the three fused hetero­cyclic rings are essentially coplanar. The crystal stacking is mainly due to π–π inter­actions and inter­molecular C—H⋯O hydrogen-bonding inter­actions.

He-Lian Chen

Papers

3‐(4‐Chlorophenyl)‐5‐methyl‐2‐propylamino‐8,9,10,11‐tetrahydro‐2‐benzothieno[2′,3′;2,3]pyrido[4,5‐d]pyrimidin‐4(3H)‐one

5‐Methyl‐2‐morpholino‐3‐p‐tolyl‐8,9,10,11‐tetrahydro‐2‐benzothieno[2′,3′:6,5]pyrido[4,3‐d]pyrimidin‐4(3H)‐one

5-Methyl-2-(2-nitrophenyloxy)-3-p-tolyl-8,9,10,11-tetrahydrobenzo[4′,5′]thieno[3′,4′:5,6]pyrido[4,3-d]pyrimidin-4(3H)-one