Synthesis and crystal structure of racemic (R*,R*)-2,2′-(1,4-phenylene)bis(3-phenyl-2,3,5,6-tetrahydro-4H-1,3-thiazin-4-one)

In the racemic title compound, C26H24N2O2S2, one of the thiazine rings shows a twisted boat conformation (Q = 0.743 Å, θ = 92.1°) and the other a half-chair puckering (Q = 0.669 Å, θ = 54.3°). The terminal phenyl rings are almost parallel to each other [dihedral angle 21.71 (10)°]. Both of these rings are orthogonal to the central phenyl ring, subtending a dihedral angle of about 78° in each case. The extended structure is consolidated by C—H...O and C—H...S hydrogen bonds as well as aromatic ring interactions of parallel-displaced and T-type. The molecule has approximate C2 local symmetry but this is not carried over to its three-dimensional structure or the intermolecular interactions.

Crystal structure and Hirshfeld surface analysis of 5,7-diphenyl-1,2,3,5,6,7-hexahydroimidazo[1,2-a]pyridine-6,6,8-tricarbonitrile methanol monosolvate

In the title compound, C22H17N5·CH4O, the imidazolidine ring of the 1,2,3,5,6,7-hexahydroimidazo[1,2-a]pyridine ring system is a twisted envelope, while the 1,2,3,4-tetrahydropyridine ring adopts a twisted boat conformation. In the crystal, pairs of molecules are linked by O—H...N and N—H...O hydrogen bonds via two methanol molecules, forming a centrosymmetric R 4 4(16) ring motif. These motifs are connected to each other by C—H...N hydrogen bonds and form columns along the a axis. The columns form a stable molecular packing, being connected to each other by van der Waals interactions. A Hirshfeld surface analysis indicates that the most significant contributions to the crystal packing are from H...H (43.8%), N...H/H...N (31.7%) and C...H/H...C (18.4%) contacts.

Crystal structures of 1-(4-chlorophenyl)-4-(4-methylphenyl)-2,5-dioxo-1,2,5,6,7,8-hexahydroquinoline-3-carboxylic acid and 4-(4-methoxyphenyl)-1-(4-methylphenyl)-2,5-dioxo-1,2,5,6,7,8-hexahydroquinoline-3-carbonitrile

In the title compounds C23H21ClN2O3 [I, namely 1-(4-chlorophenyl)-4-(4-methylphenyl)-3,8-dioxo-1,2,5,6,7,8-hexahydroquine-3-carboxylic acid] and C24H22N2O3 [II, namely 4-(4-methoxyphenyl)-1-(4-methylphenyl)-2,5-dioxo-1,2,5,6,7,8-hexahydroquinoline-3-carbonitrile], each of the cyclohexene and dihydropyridine rings of the 1,2,5,6,7,8-hexahydroquinoline moieties adopts a twisted-boat conformation. The asymmetric units of both compounds I and II consist of two independent molecules (A and B). In II A, three carbon atoms of the cyclohexene ring are disordered over two sets of sites in a 0.670 (11):0.330 (11) occupancy ratio. In the crystal of I, molecules are linked through classical N—H...O hydrogen bonds, forming inversion dimers with an R 2 2(8) ring motif and with their molecular planes parallel to the crystallographic (020) plane. Non-classical C—H...O hydrogen-bonding interactions connect the dimers, resulting in a three-dimensional network. In the crystal of II, molecules are linked by C—H...N, C—H...O and C—H...π interactions, forming a three-dimensional network.

The 1α-hydroxy-A-rings of norditerpenoid alkaloids are twisted-boat conformers

The skeletal conformations of naturally occurring norditerpenoid alkaloids fix their substituent functional groups in space, thereby directing their bioactivities.

IMDAV reaction between phenylmaleic anhydride and thienyl(furyl)allylamines: synthesis and molecular structure of (3aSR,4RS,4aRS,7aSR)-5-oxothieno- and (3aSR,4SR,4aRS,7aSR)-5-oxofuro[2,3-f]isoindole-4-carboxylic acids

The title compounds C24H21NO3S, I, and C24H21NO4, II, are the products of the IMDAV reaction between phenylmaleic anhydride and thienyl(furyl)allylamines. Their molecular structures comprise fused tricyclic systems containing thiophene, cyclohexene and pyrrolidine rings (I) or furan, cyclohexene and pyrrolidine rings (II). The central cyclohexene and pyrrolidine rings in both compounds adopt slightly twisted boat and envelope conformations, respectively. The dihedral angles between the basal plane of the pyrrolidine ring and the thiophene (in I) or furan (in II) ring plane are 22.74 (16) and 26.29 (5)°, respectively. The nitrogen atom both in I and II has practically planar environment [the sums of the bond angles are 359.8 and 358.9°, respectively]. In the crystal of I, the molecules form hydrogen-bonded zigzag chains along [010] through strong intermolecular O—H...O hydrogen bonds involving carboxylic and keto groups, whereas in the crystal of II, the molecules are joined into centrosymmetric dimers by strong O—H...O hydrogen bonds between the carboxylic groups. In II, the atoms involved into these hydrogen bonds (and hence the whole carboxylic group) are disordered over two sets of sites with an occupancy ratio of 0.6:0.4. Compounds I and II crystallize as racemates consisting of enantiomeric pairs of the 3aSR,4RS,4aRS,7aSR and 3aSR,4SR,4aRS,7aSR diastereomers, respectively.

Qualitative and quantitative analysis of intermolecular interactions in xanthenedione derivatives

The existence of intermolecular interactions and the conformational geometry adopted by molecules are related to biological activity. Xanthenedione molecules are promising and emerging antioxidants and acetylcholinesterase inhibitors. To examine the role of different functional groups involved in the intermolecular interactions and conformational geometries adopted in xanthenediones, a series of three substituted xanthenediones have been crystallized [9-(3-hydroxyphenyl)-3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione, C23H26O4, 9-(5-bromo-2-methoxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7-tetrahydro-2H-xanthene-1,8(5H,9H)-dione, C24H27BrO4, and 3,3,6,6-tetramethyl-9-(pyridin-2-yl)-3,4,6,7-tetrahydro-2H-xanthene-1,8(5H,9H)-dione, C22H25NO3] and their intermolecular interactions analyzedviaHirshfeld analysis. The results show that all the derivatives adopt the same structural conformation, where the central ring has a shallow boat conformation and the outer rings have a twisted boat conformation. The intermolecular interactions in the molecules are predominantly O—H...O, C—H...O and π–π interactions. The optimized structures of the derivatives from theoretical B3LYP/6-311G** calculations show a good correlation with the experimental structures. The lattice energy involved in the intermolecular interactions has been explored usingPIXELC.

2-Amino-4-(4-methoxyphenyl)-1-(4-methylphenyl)-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carbonitrile

In the title compound, C24H23N3O2, the cyclohexene and 1,4-dihydropyridine rings of the 1,4,5,6,7,8-hexahydroquinoline ring system each adopt a twisted-boat conformation. The dihedral angle between the benzene rings is 13.89 (10)°. In the crystal, molecules are linked through pairs of amino–nitrile N—H...N hydrogen bonds, forming inversion dimers. Weak C—H...O and C—H...π interactions connect the dimers, forming a three-dimensional network.

Ethyl 2-[9-(5-bromo-2-hydroxyphenyl)-3,3,6,6-tetramethyl-1,8-dioxo-1,2,3,4,5,6,7,8,9,10-decahydroacridin-10-yl]acetate

In the title compound, C27H32BrNO5, the central 1,4-dihydropyridine ring adopts a shallow sofa conformation (with the C atom bearing the bromophenol ring as the flap), whereas the pendant cyclohexene rings both have twisted-boat conformations. The molecule features an intramolecular O—H...O hydrogen bond, which closes anS(8) ring. In the crystal, molecules are linked by C—H...O interactions, formingC(12) chains along thec-axis direction. The ethyl acetate grouping is disordered over two sets of sites in a 0.719 (11):0.281 (11) ratio.

Crystal structure of 4,10-dimethoxy-13-methyl-6H,12H-6,12-epiminodibenzo[b,f][1,5]dioxocine

The title compound, C17H17NO4, lacks crystallographic symmetry with one molecule per asymmetric unit. The molecule exists in a folded butterfly-like conformation; the benzene rings form a dihedral angle of 84.72 (7)°. The central eight-membered imino-bridged dioxocin ring adopts a twisted-boat conformation. In the crystal, inversion-related molecules are linked by pairs of weak C—H...O hydrogen bonds, forming double-stranded chains parallel to theaaxis.