Crystal structure of 2-oxo-2H-chromen-3-yl 4-chloro-benzoate and Hirshfeld surface analysis.

In the title compound, C16H9ClO4 the dihedral angle between the coumarin ring system [maximum deviation = 0.023 (1) Å] and the benzene ring is 73.95 (8)°. In the crystal, π-π inter-actions link the dimers into a three-dimensional framework. A quantum chemical calculation is in generally good agreement with the observed structure, although the calculated dihedral angle between the ring systems (85.7%) is somewhat larger than the observed value [73.95 (8)°]. Hirshfeld surface analysis has been used to confirm and qu-antify the supra-molecular inter-actions.

Crystal structure of 3-(2-hy-droxy-eth-yl)-2-methyl-sulfanyl-6-nitro-3H-benzimidazol-1-ium chloride monohydrate.

In the cation of the title hydrated molecular salt, C10H12N3O3S+·Cl-·H2O, the benzimidazolium ring system is almost planar (r.m.s. deviation = 0.006 Å) and the nitro group is inclined at an angle of 4.86 (9)° to this plane. In the crystal, C-H⋯O hydrogen bonds form centrosymmetric R22(20) dimers and these are further aggregated through N-H⋯O and O-H⋯Cl hydrogen bonds involving the water mol-ecules and chloride anions. Aromatic π-π stacking inter-actions are also found between two parallel benzene rings or the benzene and imidazolium rings, with centroid-centroid distances of 3.5246 (9) and 3.7756 (9) Å, respectively. Analysis of the bond lengths and comparison with related compounds show that the nitro substituent is not involved in conjugation with the adjacent π-system and hence has no effect on the charge distribution of the heterocyclic ring.

Crystal structure of 2-oxo-2H-chromen-3-yl propano-ate.

In the title compound, C12H10O4, the dihedral angle between the coumarin ring system [maximum deviation = 0.033 (8) Å] and the propionate side chain is 78.48 (8)°. In the crystal, weak C-H⋯O hydrogen bonds generate inversion dimers and and C-H⋯π and π-π inter-actions link the dimers into a three-dimensional network. A quantum chemical calculation is in good agreement with the observed structure.

2-Oxo-2H-chromen-4-yl 4-methyl-benzoate.

The asymmetric unit of the title compound, C17H12O4, consists of two independent mol-ecules. The chromen-2-one ring and the 4-methyl-benzoate side chain are inclined to one another at a dihedral angle of 64.79 (10)° in one mol-ecule and 88.3 (1)° in the other. In the crystal, mol-ecules form R 2 (2)(8) centrosymmetric dimers via C-H⋯O hydrogen bonds. These dimers are stacked by C-H⋯O hydrogen bonds, resulting in R 2 (2)(18) and R 3 (2)(16) ring motifs. π-π stacking inter-actions between two parallel chromen-2-one rings, with centroid-centroid distances of 3.743 (1) and 3.771 (1) Å, are also present.

2-Oxo-2H-chromen-4-yl propionate.

In the title compound, C12H10O4, the atoms of the 2-oxo-2H-chromene ring system and the non-H atoms of the 4-substituent all lie on a crystallographic mirror plane. The mol-ecular structure exhibits an intra-molecular C-H⋯O hydrogen bond, which generates an S(6) ring. In the crystal, mol-ecules form R 3 (2)(12) trimeric units via C-H⋯O inter-actions which propagate into layers parallel to the ac plane. These layers are linked by weak C-H⋯O inter-actions along the [010] direction, generating a three-dimensional network.

2-Oxo-2H-chromen-4-yl 4-tert-butyl-benzoate.

In the title mol-ecule, C(20)H(18)O(4), the three methyl groups of the tert-butyl substituent show rotational disorder. Each methyl group is split over three positions, with refined site-occupation factors of 0.711 (4), 0.146 (3) and 0.144 (4). The benzene ring of the benzoate group is oriented at a dihedral angle of 60.70 (7)° with respect to the planar chromene ring [maximum deviation = 0.046 (2) Å]. The crystal structure features centrosymmetric R(2) (2)(8) dimers formed via C-H⋯O inter-actions, and these dimeric aggregates are connected by C-H⋯π inter-actions.

Ethyl 4-cyano-7-nitro-1,2,3,3a,4,5-hexa-hydro-pyrrolo-[1,2-a]quinoline-4-carboxyl-ate.

In the title compound, C(16)H(17)N(3)O(4), the six-membered N-containing ring adopts a half-chair conformation. One C atom of the five-membered ring is disordered over two sites, with occupancy factors of ca 0.67 and 0.33. The major pyrroline component adopts a half-chair conformation. Inter-molecular C-H⋯O hydrogen bonds forming centrosymmetric dimers are observed in the crystal.

4-[(Hy-droxy)(4-methyl-phen-yl)methyl-idene]isochroman-1,3-dione.

In the title compound, C(17)H(12)O(4), the six-membered heterocyclic ring adopts a distorted screw-boat conformation. The mol-ecular structure exhibits an S(6) ring motif, owing to an intra-molecular O-H⋯O hydrogen bond. In the crystal, weak C-H⋯O contacts generate an infinite chain along the c axis. There are also π-π stacking inter-actions between neighbouring isochromanedione benzene rings, with a centroid-centroid distance of 3.755 (1) Å, and C-O⋯π inter-actions with an O⋯centroid distance of 3.964 (2) Å.

2-Oxo-2H-chromen-4-yl 4-meth-oxy-benzoate.

In the title mol-ecule, C17H12O5, the chromen-2-one ring and the 4-meth-oxy-benzoate side chain are inclined to one another at a dihedral angle of 69.82 (9)°. The crystal structure features parallel sheets of centrosymmetric R2(2)(6) dimers joined by a C(7) chain, resulting in centrosymetric tetra-mers of hydrogen-bonded mol-ecules with graph-set motif R4(4)(40). These centrosymetric tetra-mers are connected by a pair of hydrogen bonds described by an R2(2)(8) ring motif and a C(7) chain via C-H⋯O inter-actions. In the structure, there are also π-π stacking inter-actions between chromene benzene and the six-membered heterocyclic rings [centroid-centroid distance = 3.691 (2) Å] and weak C=O⋯π inter-actions [O⋯(ring centroid) distance = 3.357 (3) Å].

4-[(4-Chloro-phen-yl)(hy-droxy)methyl-idene]isochromane-1,3-dione.

In the title compound, C(16)H(9)ClO(4), the six-membered heterocyclic ring adopts a screw-boat conformation. The benzene rings are oriented to each other at a dihedral angle of 59.26 (9)°. The mol-ecular structure exhibits a ring motif, viz. S(6), owing to an intra-molecular O-H⋯O hydrogen bond. The presence of C-H⋯O contacts generates an infinite chain along [001]. Also present are π-π stacking inter-actions between neighbouring isochromanedione benzene rings [centroid-centroid distance = 3.746 (1) Å], and C-O⋯π inter-actions [O⋯centroid = 3.934 (2) Å].

2-Oxochromen-4-yl 4-(dimethyl-amino)-benzoate.

In the title mol-ecule, C(18)H(15)NO(4), the benzoate ring is oriented at a dihedral angle of 43.43 (6)° with respect to the planar [maximum deviation = 0.038 (2) Å] chromene ring. The crystal structure features R(2) (2)(12) centrosymetric dimers formed via C-H⋯O inter-actions and these dimeric aggregates are connected by C-H⋯π inter-actions.

(E)-Ethyl 2-cyano-3-[5-nitro-2-(pyrrolidin-1-yl)phen-yl]acrylate.

The title compound, C(16)H(17)N(3)O(4), was prepared by the reaction of 5-nitro-2-(pyrrolidin-1-yl)benzaldehyde and ethyl cyano-acetate. The mol-ecular structure adopts an E conformation with respect to the C=C double bond. The five-membered ring has a half-chair conformation, with puckering parameters Q(2)= 0.399 (2) Šand ϕ = 93.1 (3)°. In the crystal, inversion dimers , linked by pairs of C-H⋯O inter-actions, are further connected through C-H⋯N hydrogen bonds. Weak slipped π-π inter-actions occur between symmetry-related benzene rings [centroid-centroid distance = 3.785 (1)Å].

An axial tert-butyl group in strained cyclohexene: X-ray analysis and theoretical calculations of 2-(2-tert-butylcyclohex-3-enyl)propan-2-ol.

The structure of the title compound, C(13)H(24)O, (I), shows a sofa conformation of the ring with two pseudo-axial substituents. The dihedral angle between these substituents is 131.56 (12) degrees . Calculations using the B3LYP/6-31G* level of theory show two minima, one corresponding to the crystal structure and the other to a boat conformation of the ring with two equatorial substituents. The energy of this latter conformation is 17.4 kcal mol(-1) higher than that of (I). The molecule forms an infinite co-operative hydrogen-bonded chain running in the b direction.