R. Ranjith Kumar

N—H...O and N—H...N interactions in three pyran derivatives

The three pyran structures 6-methylamino-5-nitro-2,4-diphenyl-4H-pyran-3-carbonitrile, C19H15N3O3, (I), 4-(3-fluorophenyl)-6-methylamino-5-nitro-2-phenyl-4H-pyran-3-carbonitrile, C19H14FN3O3, (II), and 4-(4-chlorophenyl)-6-methylamino-5-nitro-2-phenyl-4H-pyran-3-carbonitrile, C19H14ClN3O3, (III), differ in the nature of the aryl group at the 4-position. The heterocyclic ring in all three structures adopts a flattened boat conformation. The dihedral angle between the pseudo-axial phenyl substituent and the flat part of the pyran ring is 89.97 (1)° in (I), 80.11 (1)° in (II) and 87.77 (1)° in (III). In all three crystal structures, a strong intramolecular N-H···O hydrogen bond links the flat conjugated H-N-C=C-N-O fragment into a six-membered ring. In (II), molecules are linked into dimeric aggregates by N-H··· O(nitro) hydrogen bonds, generating an R2(2)(12) graph-set motif. In (III), intermolecular N-H···N and C-H···N hydrogen bonds link the molecules into a linear chain pattern generating C(8) and C(9) graph-set motifs, respectively.

(E)-16-(4-Chloro­benzyl­idene)estrone

In the title compound, C25H25ClO2, the C ring adopts a chair conformation, while the B ring approximates a half-chair conformation. The five-membered ring D has a twist conformation on the C—C bond fused with the C ring. Aromatic rings A and E are not coplanar, as evidenced by the dihedral angle of 7.51 (1)°. In the crystal, O—H⋯O hydrogen bonds form a double chain along the ab plane interconnected by C—H⋯O interactions.

rac-2-Hy­droxy-2-(2-oxocyclo­pent­yl)-1H-indene-1,3(2H)-dione

In the title compound, C(14)H(12)O(4), the indene unit is essentially planar [r.m.s. deviation = 0.0309 (1) Å] and the cyclo-penta-none ring adopts a twist form. In the crystal, mol-ecules are joined via pairs of O-H⋯O hydrogen bonds into centrosymmetric dimers.

3-[(E)-2,4-Dichloro­benzyl­idene]-1-methyl­piperidin-4-one

The piperidine ring of the title compound, C13H13Cl2NO, adopts an envelope conformation. Intermolecular C—H⋯O interactions link the molecules into a C(7) chain running along the b axis.

Crystal structure of 5-benzoyl-2,4-di­phenyl-4,5-di­hydro­furan-3-carbo­nitrile

In the title compound, C24H17NO2, the carbonyl O atom of the benzoyl group is cis with respect to the furanyl O atom, and the associated O—C—C—O torsion angle is 4.62 (19)°. The puckering of the dihydrofuran ring is close to twisted (4 T 5), with parameters Q = 0.1856 (16) Å and φ = 313.5 (5)°. Molecules are interconnected via a C—H⋯N and a C—H⋯O hydrogen bond, leading to layers parallel to the (200) plane and characterized by R 4 4(28) and R 4 4(36) graph-set motifs. The furan O atom does not participate in intermolecular hydrogen bonding. The crystal lattice encompasses a solvent-accessible void of 24.7 (8) Å3.

Crystal structure of 2-hy-droxy-2-(2-oxo-cyclo-hept-yl)-2,3-di-hydro-1H-indene-1,3-dione.

In the title compound, C16H16O4, the five-membered ring of the indene-1,3-dione unit adopts a twist conformation, whereas the seven-membered ring adopts a twist–chair conformation. In the crystal, molecules are linked by O—H⋯O hydrogen bonds, weak C—H⋯O hydrogen bonds and π–π stacking [centroid-to-centroid distance = 3.7373 (8) Å] into a three-dimensional supramolecular architecture.

C-H···O and C-H···N interactions in three hexahydrocycloocta[b]pyridine-3-carbonitriles.

The structures of three new pyridine derivatives, 2-methoxy-4-(4-methoxyphenyl)-5,6,7,8,9,10-hexahydrocycloocta[b]pyridine-3-carbonitrile, C20H22N2O2, (I), 2-ethoxy-4-(3-nitrophenyl)-5,6,7,8,9,10-hexahydrocycloocta[b]pyridine-3-carbonitrile, C20H21N3O3, (II), and 2-ethoxy-4-(4-methoxyphenyl)-5,6,7,8,9,10-hexahydrocycloocta[b]pyridine-3-carbonitrile, C21H24N2O2, (III), differ in the nature of the substituents either at the 2-position of the central pyridine ring or on the pendent aryl ring. This simple change in the structure substantially alters the intermolecular interaction patterns. The substituted phenyl group adopts a synclinal geometry with respect to the plane of the pyridine ring in all three compounds. In (I), a C-H···N interaction results in a one-dimensional chain parallel to the b axis. In (II), there are two C-H···N(nitrile) interactions from different symmetry-related molecules, resulting in a two-dimensional network parallel to the bc plane. There is also a weak C-H···O interaction from the ethoxy group to an adjacent nitro O atom. The present work is an example of how the simple replacement of a substituent in the main molecular scaffold may transform the structure type, paving the way for a variety of supramolecular motifs and consequently altering the complexity of the intermolecular interaction patterns.

(3aR,8bR)-3a,8b-Dihy­droxy-2-methyl­sulfanyl-3-nitro-1-phenyl-1,8b-di­hydro­indeno[1,2-b]pyrrol-4(3aH)-one

In the title compound, C18H14N2O5, the pyrrolidine ring adopts a shallow envelope conformation, with the C atom bearing the OH group (and remote from the N atom) displaced by 0.257 (2) Å from the other atoms. The cyclopentane ring has a twisted conformation about the C—C bond bearing one =O and one —OH grouping. The dihedral angle between the five-membered rings (all atoms) is 65.54 (9)° and the OH groups lie to the same side of the ring-junction. The molecular structure features a weak intramolecular O—H⋯O bond and a possible C—H⋯π interaction. In the crystal, the molecules are linked into [010] chains by O—H⋯O hydrogen bonds. Weak C—H⋯O bonds connect the chains into (100) sheets.

1-Methyl-1'-(4-methyl-phen-yl)-2',3',5',6',7',7a'-hexa-hydro-1'H-dispiro-[piperidine-3,2'-pyrrolizine-3',3''-indoline]-4,2''-dione.

The title compound, C26H29N3O2, crystallizes with two molecules in the asymmetric unit, having C—H⋯O interactions between them and resulting in a dimer characterized by an R 2 2(11) motif. These dimers are linked into an ABABAB chain via N—H⋯O, N—H⋯N and C—H⋯O built edge-fused R 1 2(5) and R 2 2(7) motifs. This chain is linked to its inversion-related partner via N—H⋯O bonds with an R 2 2(8) motif and leads to a double chain extending along the b axis characterized by an R 6 6(36) motif across the inversion centres. The methyl group of the phenyl ring and the oxindole of molecule A and B are involved in C—H⋯π interactions. One C atom of the pyrrolizine ring of molecule A and its attached H atoms show positional disorder, the major and minor components being in the ratio 0.706 (7):0.294 (7).

2-Amino-4-(4-chloro-phen-yl)-5,6,7,8,9,10-hexa-hydro-benzo[8]annulene-1,3-dicarbonitrile.

In the title compound, C20H18ClN3, the cyclooctene ring exhibits conformational disorder of two methylene groups with a site-occupation factor of 0.859 (6) for the major occupied site. In the crystal, molecules are connected into inversion dimers via pairs of weak N—H⋯N hydrogen bonds, forming an R 2 2(12) graph-set motif. These dimers are further connected via weak N—H⋯Cl interactions into chains running along [011]. There are also C—H⋯N interactions present in the crystal.