Highly regio- and diastereo-selective synthesis of novel tri- and tetra-cyclic perhydroquinoline architectures via an intramolecular [3 + 2] cycloaddition reaction

A facile and efficient synthetic protocol was established for the construction of novel tri- and tetra-cyclic pyrrolo/pyrrolizinoquinoline architectures via the in situ formation of azomethine ylide followed by an intramolecular [3 + 2] cycloaddition reaction strategy. This protocol leads to the creation of two/three new rings and three/four contiguous stereocentres, in which one of them is a tetra-substituted carbon center, in a highly diastereoselective fashion with excellent yields.

Crystal structures and conformational analyses of three pyranochromene derivatives

The title compounds, C27H20O6, (I) [systematic name: methyl 7-oxo-14-phenyl-1H,7H,14H-pyrano[3,2-c:5,4-c']dichromene-14a(6bH)-carboxyl-ate], C24H22O5, (II) [systematic name: methyl 1-oxo-6-phenyl-2,3,4,12b-tetra-hydro-1H,6H-chromeno[3,4-c]chromene-6a(7H)-carboxyl-ate], and C25H23N3O4, (III) [systematic name: 6-(4-ethyl-phen-yl)-2,4-dimethyl-1,3-dioxo-2,3,4,12b-tetra-hydro-1H,6H-chromeno[4',3':4,5]pyrano[2,3-d]pyrimidine-6a(7H)-carbo-nitrile], are pyran-ochromene derivatives. The central pyran rings (B) of compounds (I) and (III) adopt half-chair conformations, whereas that of compound (II) adopts a sofa conformation. The pyran rings (A) of the chromene ring systems of compounds (II) and (III) adopt half-chair conformations, while that of compound (I) adopts a sofa conformation. The mean plane of the central pyran rings (B) make dihedral angles of 70.02 (6), 61.52 (6) and 69.12 (7)°, respectively, with the mean planes of the chromene moieties (C+A) of compounds (I), (II) and (III). The bicyclic coumarin ring system (C+A+B+E) in compound (I) is almost planar (r.m.s. deviation = 0.042 Å). The carbo-nitrile side chain in compound (III) is very nearly linear, with the C-C N angle being 176.6 (2)°. The cyclo-hexene ring (E), fused with the central pyran ring (B) in compound (II) adopts a sofa conformation. In the mol-ecular structures of compounds (II) and (III), there are C-H⋯O short contacts, which generate S(7) ring motifs. In the crystal structures of the title compounds, mol-ecules are linked by C-H⋯O hydrogen bonds, which generate mol-ecular sheets parallel to the ab plane, with R 4 (3)(28) loops in (I), inversion dimers with R 2 (2)(10) loops in (II) and chains along [010] with R 2 (2)(12) ring motifs in (III). In the crystal structures of (I) and (III), there are also C-H⋯π inter-actions present, leading to the formation of a three-dimensional framework in (II) and to sheets parallel to (101) in (III).

Crystal structure of (Z)-3-(4-meth-oxy-benzyl-idene)-2,3-di-hydro-benzo[b][1,4]thia-zepin-4(5H)-one

In the title compound, C₁₇H₁₅NO₂S, the two C atoms linking the S and carbonyl C atoms of the seven-membered thia­zepine ring are disordered over two sites, with occupancies of 0.511 (4) and 0.489 (4); both disorder components adopt distorted twist-boat conformations. In the crystal, N—H⋯O and C—H⋯O hydrogen bonds link inverted-related mol­ecules into dimers, incorporating R₁²(6) and R₂²(8) ring motifs; the acceptor carbonyl O atom is bifurcated. These dimers are further linked by C—H⋯O hydrogen bonds, forming supra­molecular tapes running along the a axis.

Crystal structure of methyl 6-methoxy-11-(4-methoxyphenyl)-16-methyl-14-phenyl-8,12-dioxa-14,15-diazatetracyclo[8.7.0.02,7.013,17]heptadeca-2(7),3,5,13(17),15-pentaene-10-carboxylate

In the title compound, C30H28N2O6, the pyran ring adopts a slightly distorted half-chair conformation and the pyrone ring adopts an envelope conformation, with the C atom bearing the carboxylate group as the flap. The pyrazole ring [maximum deviation = 0.002 (2) Å] forms a dihedral angle of 13.2 (1)° with the attached benzene ring. The near-planar atoms of the pyran ring and the pyrazole ring are close to coplanar, the dihedral angles between their mean planes being 6.4 (1)°. The dihedral angle between the pyrone ring and the benzene ring of the chromene unit is 10.7 (1)°. The molecular conformation is stabilized by an intramolecular C—H...O hydrogen bond, which generates anS(6) ring motif. In the crystal, C—H...O interactions generate supramolecular chains propagating in [100] and these are connected into double layers that stack along thec-axis direction by weak π–π interactions between pyrazole rings [centroid–centroid distance = 3.801 (1) Å].

Methyl (E)-3-(2-formylphenoxy)acrylate

In the title compound, C₁₁H₁₀O₄, the methyl acrylate sub­stituent adopts an extended E conformation with all torsion angles close to 180°. The conformation of the keto group with respect to the olefinic double bond is typically S-trans. In the crystal, mol­ecules are linked via pairs of C—H⋯O hydrogen bonds, forming inversion dimers with an R₂²(8) graph-set motif. The dimers are further linked via C—H⋯O hydrogen bonds, forming chains along [001], which enclose R₃²(16) graph-set ring motifs. The keto group O atomaccepts two C—H⋯O interactions.

Methyl 1-phenyl-3-p-tolyl-1,9b-dihydro-3H-chromeno[4,3-c]isoxazole-3a(4H)-carboxylate

In the title compound, C25H23NO4, the pyran ring of the chroman moiety has an envelope conformation with the methylene C atom as the flap. The isoxazole ring has a twist conformation on the O—C bond. The dihedral angle between their mean planes is 57.87 (9)°. The attached phenyl and benzene rings are twisted away from its mean plane by 56.19 (10) and 50.57 (10)°, respectively. These two rings are normal to each other, subtending a dihedral angle of 89.2 (1)°. In the crystal, there are no classical hydrogen bonds; the molecules are linkedviaC—H...π interactions, forming a two-dimensional network lying parallel to (10-1).

8-Bromo-3-(4-ethyl-phen-yl)-1-phenyl-3,3a,4,9b-tetra-hydro-1H-chromeno[4,3-c]isoxazole-3a-carbo-nitrile

In the title compound, C25H21BrN2O2, the fused isoxazolidine ring adopts an envelope conformation with the N atom at the flap and the mean plane of the ring makes dihedral angles of 54.37 (12) and 87.32 (13)°, respectively, with the adjacent phenyl and benzene rings. The tetra-hydro-pyran ring has a half-chair conformation. In the crystal, mol-ecules are linked into a double-column structure along the b-axis direction through weak C-H⋯O and C-H⋯π inter-actions.

Methyl 3′-benzyl-4′-(2-chlorophenyl)-1′-methyl-2-oxospiro[indoline-3,2′-pyrrolidine]-3′-carboxylate

In the title compound, C₂₇H₂₅ClN₂O₃, the methyl­pyrrolidine ring adopts an envelope conformation with the N atom at the flap. The mean plane of the pyrrolidine ring makes dihedral angles of 82.1 (1), 84.4 (1) and 79.8 (1)°, respectively, with the adjacent benzene ring, the mean plane of the indoline ring system and the phenyl ring. The mol­ecular structure is stabilized by intra­molecular C—H⋯O hydrogen bonds. In the crystal, mol­ecules are linked into chains along [101] by N—H⋯O hydrogen bonds. C—H⋯π inter­actions are observed between the chains.

14-Methoxy-4,6-dimethyl-9-phenyl-8,12-dioxa-4,6-diazatetracyclo[8.8.0.02,7.013,18]octadeca-2(7),13,15,17-tetraene-3,5,11-trione

The title compound, C₂₃H₂₀N₂O₆, crystallizes with two mol­ecules in the asymmetric unit in which the dihedral angles between the mean planes of the pyran and phenyl rings are 66.6 (1) and 61.9 (1) °. The fused pyrone and pyran rings each adopts a sofa conformation. In the crystal, C—H⋯O hydrogen bonds link the mol­ecules, forming a two-dimensional network parallel to [001].

(E)-2-Bromo-methyl-3-(o-tol-yl)acrylo-nitrile

The title compound C11H10BrN, has an E conformation at the C=C bond of the acrylo-nitrile unit. The vinyl group makes a dihedral angle of 44.53 (12)° with the benzene ring. In the crystal, weak C-H⋯π inter-actions involving the benzene ring are observed.

(E)-2-[(2-Formyl-phen-oxy)meth-yl]-3-(4-iso-propyl-phen-yl)acrylo-nitrile

In the title compound, C20H19NO2, the dihedral angle between the benzene rings is 77.12 (8)°. The terminal isopropyl group is disordered over two orientations, with site occupancies of 0.720 (14) and 0.280 (14). In the crystal, mol-ecules are linked through a weak C-H⋯O inter-action, forming a zigzag chain along the c-axis direction.

Methyl 2-[(2-chloro-quinolin-3-yl)(hy-droxy)meth-yl]acrylate

There are two independent mol-ecules (A and B) in the asymmetric unit of the title compound, C14H12ClNO3. The mean planes of the methyl ester unit (Cmeth-yl-O-C=O; r.m.s. deviation = 0.051 Å for mol-ecule A and 0.016 Å for mol-ecule B) and the chloro-quilonine ring system (r.m.s. deviation = 0.023 Å for mol-ecule A and 0.014 Å for mol-ecule B) form dihedral angles of 63.5 (1)° in mol-ecule A and 78.1 (1)° in mol-ecule B. The main difference between the two independent mol-ecules is reflected in the (H)O-C-C=C(H2) torsion angle which is -109.7 (2)° in mol-ecule A and 10.6 (2)° in mol-ecule B. An intra-molecular O-H⋯O hydrogen bond is observed in mol-ecule A. In the crystal, mol-ecules A and B are linked into pairs via bifurcated O-H⋯(N,Cl) hydrogen bonds and a weak C-H⋯O hydrogen bond links pairs of mol-ecules into chains along [100].

rac-3-(4-Chlorophenyl)-3a,4-dihydro-3H-chromeno[4,3-c]isoxazole-3a-carbonitrile

The title compound, C₁₇H₁₁ClN₂O₂, which contains two stereogenic C atoms, crystallizes in a centrosymmetric space group as a racemate. The pyran ring and the isoxazole ring adopt sofa and twisted conformations, respectively. The dihedral angle between the benzene ring and the mean plane through the near coplanar atoms of the pyran ring is 4.17 (5)°. The mol­ecular conformation features a weak C—H⋯O contact. In the crystal, C—H⋯O hydrogen bonds link the mol­ecules, forming chains along the a-axis direction.

3-(4-Methoxybenzyl)-1,5-benzo-thiazepin-4(5H)-one

In the title compound, C17H15NO2S, the thia-zepine ring adopts a slightly distorted twist-boat conformation. The dihedral angle between the mean plane of the benzo-thia-zepin ring system and the benzene ring is 65.7 (1)°. In the crystal, pairs of N-H⋯O hydrogen bonds link inversion-related mol-ecules into dimers, generating R2 (2) (8) ring motifs. These dimers are further linked by C-H⋯π and π-π inter-actions [inter-centroid distance between the benzene rings of the benzo-thia-zepine unit = 3.656 (3) Å] into a three-dimensional supra-molecular network.

(Z)-3-(3,4-Di-meth-oxy-benz-yl)-1,5-benzo-thia-zepin-4(5H)-one

In the title compound, C₁₈H₁₇NO₃S, the thia­zepine ring adopts a slightly distorted twist-boat conformation. The dihedral angle between the mean plane of the benzo­thia­zepin ring system and the benzene ring is 60.3 (1)°. In the crystal, mol­ecules are linked by two pairs of inversion-related N—H⋯O and C—H⋯O hydrogen bonds, generating alternating R₂²(8) and R₂²(6) ring motifs, respectively, in a zigzag supra­molecular chain that runs along the c axis. These chains stack along the a axis via S⋯C [3.424 (2) Å] contacts. A three-dimensional supra­molecular network is consolidated by C—H⋯π and π–π inter­actions [inter-centroid distance between di­meth­oxy­benzene rings = 3.815 (1) Å]. The crystal studied was a non-merohedral twin, with a refined value of the minor twin fraction of 0.2477 (6) .

2-[(2-Chloro-quinolin-3-yl)(hy-droxy)meth-yl]acrylo-nitrile

In the title compound, C13H9ClN2O, the dihedral angle between the acrylo-nitrile C=C-CN plane and the quilonine ring system is 71.3 (2)°. In the crystal, mol-ecules are linked by O-H⋯N hydrogen bonds, forming chains along [01-1]. The chains are linked into a three-dimensional network through C-H⋯N inter-actions.

rac-Methyl 3-(2-meth-oxy-phen-yl)-3a,4-di-hydro-3H-chromeno[4,3-c]isoxazole-3a-carboxyl-ate

The title compound, C19H17NO5, comprising two stereogenic C atoms of the same configuration, crystallizes in a centrosymmetric space group as a racemate. The pyran ring adopts a half-chair conformation, while the isoxazole ring adopts an envelope conformation with the C atom bonded to the meth-oxy-phenyl group as the flap. The dihedral angle between the mean plane of the pyran ring and the adjacent benzene ring is 5.86 (5)°. In the crystal, mol-ecules are linked by a weak C-H⋯O hydrogen bond, forming a chain along the a axis.

(Z)-3-(2,4-Dichloro-benz-yl)-1,5-benzo-thia-zepin-4(5H)-one

In the title compound, C₁₆H₁₁Cl₂NOS, the seven-membered thia­zepine ring adopts a distorted twist-boat conformation. The dihedral angle between the mean plane of the benzothia­zepine ring system and the benzene ring is 78.6 (1)°. The mol­ecular conformation is stabilized by a weak intra­molecular C—H⋯Cl hydrogen bond, which generates an S(5) ring motif. In the crystal, pairs of N—H⋯O hydrogen bonds link inversion-related mol­ecules into dimers, generating R₂²(8) ring motifs. The crystal packing also features alternating π–π inter­actions between benzothia­zepine benzene rings [inter-centroid distance = 3.740 (3) Å] and dichloro­benzene rings [inter-centroid distance = 3.882 (3) Å] to consolidate a three-dimensional architecture.

(Z)-3-(3,4-Dimeth-oxy-benzyl-idene)-2,3-dihydro-1,5-benzothia-zepin-4(5H)-one

In the title compound, C₁₈H₁₇NO₃S, the seven-membered thia­zepine ring adopts a slightly distorted sofa conformation. The dihedral angle between the mean plane of the benzothia­zepine ring system and the benzene ring is 5.9 (1)°. The mol­ecular conformation is stabilized by an intra­molecular C—H⋯S hydrogen bond, which generates an S(7) ring motif. In the crystal, N—H⋯O and C—H⋯O hydrogen bonds link inversion-related mol­ecules into dimers, incorporating R₁²(6) and R₂²(8) ring motifs; the acceptor O atom is bifurcated. These dimers are further linked by C—H⋯O hydrogen bonds, forming supra­molecular tapes running along the a axis. These are connected into the three-dimensional architecture by C—H⋯π inter­actions.

[4-(4-Meth-oxy-phen-yl)-1-methyl-3-nitro-pyrrolidin-3-yl]methanol

In the title compound, C13H18N2O4, the dihedral angle between the benzene and pyrrolidine (all atoms) rings is 70.6 (1)°. The pyrrolidine ring adopts a half-chair conformation. In the crystal, mol-ecules form chains along the c-axis direction linked by O-H⋯N hydrogen bonds, which are then connected by C-H⋯O inter-actions, forming a sheet parallel to the bc plane.

Methyl 6-ethoxy-3-phenyl-3a,4-dihydro-3H-chromeno[4,3-c]isoxazole-3a-carboxylate

In the title compound, C₂₀H₁₉NO₅, the dihedral angle between the mean plane of the pyran ring (which has a half-chair conformation) and the benzene ring of the chromeno ring system is 7.21 (7)°. The dihedral angle between the mean plane of the chromeno ring system and the isoxazole ring is 21.78 (6)°, while the isoxazole ring forms a dihedral angle of 72.60 (8)° with the attached phenyl ring. In the crystal, mol­ecules are linked via pairs of C—H⋯O hydrogen bonds, forming inversion dimers with an R²₂(10) ring motif. These dimers are linked via C—H⋯N hydrogen bonds, forming chains along [001].

Methyl 4′-(4-fluorophenyl)-1′-methyl-3′-nitromethyl-2-oxospiro[indoline-3,2′-pyrrolidine]-3′-carboxylate

In the title compound, C₂₁H₂₀FN₃O₅, the the pyrrolidine ring makes dihedral angles of 84.91 (6) and 62.38 (7)° with the oxindole unit and the fluoro­phenyl ring, respectively. The pyrrolidine ring assumes an envelope conformation with the spiro C atom as the flap. The crystal packing features weak N—H⋯N and C—H⋯O hydrogen bonds.

(6bS*,14R*,14aR*)-Methyl 14-(4-methyl-phen-yl)-7-oxo-6b,6c,7,12b,14,14a-hexa-hydro-1H-pyrano[3,2-c:5,4-c']dichromene-14a-carboxyl-ate

In the title compound, C(28)H(22)O(6), the chromeno ring system is almost planar, with a dihedral angle between the mean planes of the pyran and benzene rings of 1.87 (8)°. The pyran ring bearing the methyl-phenyl substituent has a half-chair conformation while the other pyran ring has an envelope conformation with the tetra-substituted C atom as the flap. The benzene ring of the chromeno ring system is inclined to the benzene ring fused to the latter pyran ring by 74.66 (9)°. These aromatic rings are inclined to the 4-methyl-phenyl ring by 52.67 (9) and 66.63 (10)°, respectively. In the crystal, mol-ecules are linked via C-H⋯O hydrogen bonds, forming a two-dimensional network parallel to the bc plane.

14-Eth-oxy-4,6,9-trimethyl-8,12-dioxa-4,6-diaza-tetra-cyclo-[8.8.0.0(2,7).0(13,18)]octa-deca-2(7),13,15,17-tetra-ene-3,5,11-trione

In the title compound, C₁₉H₂₀N₂O₆, the pyrone and pyran rings adopt envelope conformations with the same common C atom as the flap, the dihedral angle between the planes of the remaining ring atoms being 68.27 (4)°. The planar atoms of the pyran ring and the diaza­cyclic ring are almost coplanar, the dihedral angle between their mean planes being 3.29 (7)°. Moreover, the planar atoms of the pyrone ring and benzene ring of the coumarin unit are also close to coplanar, the dihedral angle between their mean planes being 8.03 (9)°. The meth­oxy group lies in the plane of the benzene ring, with a dihedral angle between their mean planes of 9.4 (2)°. In the crystal, the molecules are linked by C—H⋯O hydrogen bonds resulting in sheets of mol­ecules in the ac plane.

8-Bromo-3-phenyl-3a,4-dihydro-3H-chromeno[4,3-c]isoxazole-3a-carbo-nitrile

In the title compound, C(17)H(11)BrN(2)O(2), the five-membered isoxazole ring has an envelope conformation with the C atom bearing the phenyl ring as the flap. The pyran ring has a half-chair conformation. In the chromeno ring system, the dihedral angle between the mean plane of the pyran ring and the benzene ring is 4.68 (2)°. The dihedral angle between the mean planes of the chromeno ring system and the isoxazole ring is 13.79 (15)°. The latter forms a dihedral angle of 34.10 (17)° with the phenyl ring. In the crystal, mol-ecules are linked by C-H⋯N hydrogen bonds, forming an undulating two-dimensional network parallel to the ab plane.

3-(2-Methyl-phen-yl)-3a,4-dihydro-3H-chromeno[4,3-c]isoxazole-3a-carbo-nitrile

In the title compound, C(18)H(14)N(2)O(2), the pyran ring of the chromeno ring system has a half-chair conformation, and the dihedral angle between its mean plane and the benzene ring is 5.3 (2)°. The isoxazole ring forms a dihedral angle of 74.6 (2)° with the attached benzene ring and is inclined to the mean plane of the chromeno ring system by 15.06 (19)°. In the crystal, there are no significant inter-molecular inter-actions.

14-Eth-oxy-4,6-dimethyl-9-phenyl-8,12-dioxa-4,6-diaza-tetra-cyclo-[8.8.0.0(2,7).0(13,18)]octa-deca-2(7),13,15,17-tetra-ene-3,5,11-trione

In the title compound, C₂₃H₂₀N₂O₆, the fused pyrone and pyran rings each adopt a sofa conformation. The dihedral angle between the mean planes of the pyran and phenyl rings is 61.9 (1)°. In the crystal, mol­ecules are linked by two pairs of C—H⋯O hydrogen bonds, forming dimers. These dimers are linked via a third C—H⋯O hydrogen bond, forming a two-dimensional network parallel to (10-2).

Methyl (E)-2-cyano-3-(6-nitro-1,3-benzodioxol-5-yl)acrylate

In the title compound, C₁₂H₈N₂O₆, the 1,3-benzodioxole ring system is essentially planar [maximum deviation = 0.036 (2) Å] and the nitro group is oriented at a dihedral angle of 15.4 (1)° with respect to its mean plane. In the crystal, moleucles are linked into C(8) [101] chains by C—H⋯O hydrogen bonds, and weak aromatic π–π stacking [centroid–centroid distance = 3.887 (1) Å] also occurs.

(E)-3-(1,3-Benzodioxol-5-yl)-2-{[N-(2-formylphenyl)-4-methylbenzenesulfon-amido]methyl}prop-2-enenitrile

In the title compound, C(25)H(20)N(2)O(5)S, the benzodioxole ring system is essentially planar [maximum deviation = 0.021 (2) Å] and forms dihedral angles of 85.2 (1) and 74.2 (1)°, respectively, with the formyl benzene and sulfonyl-bound benzene rings. In the crystal, C-H⋯O hydrogen bonds generate C(8) chains along [100] and R(3) (3)(19) ring motifs. In addition, a weak π-π inter-action [centroid-centroid distance = 3.937 (3) Å] is also observed.

(Z)-3-Benzyl-1,5-benzothia-zepin-4(5H)-one

In the crystal structure of the title compound, C(16)H(13)NOS, mol-ecules are linked into cyclic centrosymmetric R(2) (2)(8) dimers via pairs of N-H⋯O hydrogen bonds. The seven-membered ring adopts a boat conformation.

2-(2-Nitrophenyl)-1,3-benzothiazole

In the title compound, C₁₃H₈N₂O₂S, the essentially planar benzothia­zole system [maximum deviation = −0.012 (1) Å for the S atom] is oriented at a dihedral angle of 48.3 (1)° with respect to the benzene ring. The nitro group is substanti­ally twisted from the plane of its attached benzene ring [dihedral angle = 52.0 (1)°]. The crystal packing features C—H⋯O hydrogen bonds, which generate C(6) helical chains propagating along [010]. Weak C—H⋯π inter­actions also occur in the crystal.

2-[Hy-droxy(2-meth-oxy-phenyl)methyl]acrylonitrile

In the title compound, C₁₁H₁₁NO₂, the mean planes formed by the benzene ring and the C and N atoms of the acryl group are almost orthogonal to each other, with a dihedral angle of 85.7 (1)°. During the structure analysis, it was observed that the unit cell contains large accessible voids, with a volume of 186.9 ų, which may host disordered solvent mol­ecules. This affects the diffraction pattern, mostly at low scattering angles. Density identified in these solvent-accessible areas was calculated and corrected for using the SQUEEZE routine in PLATON [Spek (2009 ▶), Acta Cryst. D65, 148–155]. Despite the presence of the hy­droxy group in the mol­ecule, no classical or nonclassical hydrogen bonds are observed in the structure. This may reflect the fact that the O—H group points towards the solvent-accessible void.

2,2′-Diisopropoxy-5,5′-methylenedibenzaldehyde

Mol­ecules of the title compound, C₂₁H₂₄O₄, are located on a twofold rotation axis running through the central methyl­ene C atom. The aldehyde group is coplanar with the benzene ring [C—C—C—O = 175.7 (4) °].

(2E,2′E)-Dimethyl 2,2′-[(phenylazanediyl)bis(methylene)]bis(3-phenylacrylate)

The C=C double bonds in the title compound, C₂₈H₂₇NO₄, adopt an E conformation. In the crystal, pairs of C—H⋯O hydrogen bonds link the mol­ecules into inversion dimers.

(E)-Methyl 2-[(1,3-dioxoisoindolin-2-yl)methyl]-3-phenylacrylate

In the title compound, C₁₉H₁₅NO₄, the isoindole ring system is essentially planar [maximum deviation = 0.011 (1) Å] and is oriented at a dihedral angle of 75.7 (1)° with respect to the phenyl ring. The mol­ecular conformation is stabilized by an intra­molecular C—H⋯O hydrogen bond. The crystal packing is stabilized by C—H⋯O hydrogen bonds, which generate zigzag chains along the a axis. The crystal packing is further stabilized by a C—H⋯π inter­action.

(Z)-3-(2-Meth-oxy-benz-yl)-1,5-benzo-thia-zepin-4(5H)-one

In the title compound, C₁₇H₁₅NO₂S, the seven-membered thia­zepine ring adopts a distorted twist-boat conformation. The dihedral angle between the mean planes of the benzothia­zepin ring system and the attached benzene ring is 47.7 (1)°. In the crystal, pairs of N—H⋯O hydrogen bonds link inversion-related mol­ecules into dimers, generating R₂²(8) ring motifs. These dimers are further connected into a chain along the a axis by C—H⋯O hydrogen bonds, resulting in R₂²(14) ring motifs. The crystal packing also features C—H⋯π inter­actions.

(Z)-3-(4-Chloro-benz-yl)-1,5-benzothia-zepin-4(5H)-one

In the title compound, C(16)H(12)ClNOS, the seven-membered thia-zepine ring adopts a distorted twisted boat conformation. The dihedral angle between the least-squares planes of the 1,5-benzothia-zepine ring system and the benzene ring is 50.2 (1)°. In the crystal, pairs of N-H⋯O hydrogen bonds link centrosymmetrically related mol-ecules into dimers, generating R(2) (2)(8) ring motifs. The crystal packing is further stabilized by π-π inter-actions [centroid-centroid distance = 3.763 (2) Å].

2-Formyl-6-meth-oxy-phenyl cinnamate

In the title compound, C(17)H(14)O(4), the C=C bond adopts an E conformation and the dihedral angle between the benzene rings is 73.9 (1)°. The crystal packing features C-H⋯O hydrogen bonds, which generate C(4) chains propagating along the b-axis direction. Weak aromatic π-π stacking inter-actions [centroid-centroid distance = 3.703 (1) Å] are also observed.

(Z)-3-(2-Chloro-benz-yl)-1,5-benzothia-zepin-4(5H)-one

In the crystal structure of the title compound, C₁₆H₁₂ClNOS, the mol­ecules are linked into centrosymmetric R₂²(8) dimers via pairs of N—H⋯O hydrogen bonds. The seven-membered ring adopts a boat conformation.

rac-Methyl 3-(2-meth-oxy-phen-yl)-1-phenyl-3,3a,4,9b-tetra-hydro-1H-chromeno[4,3-c]isoxazole-3a-carboxyl-ate

The title compound, C₂₅H₂₃NO₅, comprising two stereogenic carbon atoms of the same configuration, crystallizes in a centrosymmetric space group as a racemate. The six-membered pyran ring and the five-membered isoxazole ring adopt sofa and twisted conformations, respectively. The dihedral angle between the benzene ring and the mean plane through the near coplanar atoms of the pyran ring is 10.73 (7)°. The crystal structure features C—H⋯O hydrogen bonds.

Methyl (E)-2-({2-[(E)-(hy-droxy-imino)-meth-yl]phen-oxy}meth-yl)-3-(4-methyl-phen-yl)acrylate

In the title compound, C(19)H(19)NO(4), the dihedral angle between the mean planes through the benzene rings is 82.18 (7)°. The C=N double bond is trans-configured. The mol-ecules are linked into centrosymmetric dimers via pairs of O-H⋯N hydrogen bonds with the motif R(2) (2)(6). The crystal packing also features C-H⋯O inter-actions. The methyl group attached to one of the aromatic rings is disordered over two almost equally occupied positions [occpancy ratio = 0.51 (4):0.49 (4)].

1-Methyl-3-(2-methyl-phen-yl)-3a-nitro-1,2,3,3a,4,9b-hexa-hydro-chromeno[4,3-b]pyrrole

The asymmetric unit of the title compound, C(19)H(20)N(2)O(3), contains two independent mol-ecules in both of which the pyrrolidine ring adopts an envelope conformation, but with a C atom as the flap in one mol-ecule and the N atom in the other. The pyran ring adopts a half-chair conformation in both mol-ecules. In the crystal, mol-ecules are linked via C-H⋯O hydrogen bonds and C-H⋯π inter-actions.

Methyl (E)-2-[(2-nitro-phen-oxy)meth-yl]-3-phenyl-acrylate

The title compound, C₁₇H₁₅NO₅, adopts an E conformation with respect to the C=C double bond of the phenyl­acrylate unit. The phenyl ring and methyl acrylate group of the phenyl­acrylate unit are disordered over two sets of sites with site-occupancy ratios of 0.705 (5):0.295 (5) and 0.683 (3):0.317 (3), respectively. The mean plane through the benzene ring of the phenyl acrylate makes dihedral angles of 88.4 (8) (major component) and 86.7 (8)° (minor component) with the nitro­phen­oxy ring; the dihedral angle between the two components is 3.64 (6)°. Intra­molecular C—H⋯O interactions stabilise the molecular structure. In the crystal, C—H⋯O inter­actions result in a chain of mol­ecules running along the b axis.

rac-6-Ethoxy-3,3a,4,9b-tetrahydro-1,3-diphenyl-1H-chromeno[4,3-c]isoxazole-3a-carbonitrile

The title compound, C₂₅H₂₂N₂O₃, with three stereogenic centres, crystallizes in a centrosymmetric space group as a racemate. The pyran ring adopts a sofa conformation and the five-membered isoxazole ring exhibits an envelope conformation. The dihedral angle between the benzene ring and the mean plane through the near coplanar atoms of the pyran ring is 10.54 (9)°. In the crystal, no significant intermolecular interactions are observed.

Methyl (2E)-2-({2-[(2E)-2-benzylidene-3-methoxy-3-oxopropyl]-1,3-dioxoindan-2-yl}methyl)-3-phenylprop-2-enoate

In the title compound, C₃₁H₂₆O₆, the five-membered ring of the indane unit adopts a slight envelope conformation with the flap atom displaced by 1.38 (14) Å. The mol­ecular conformation is stabilized by an intra­molecular C—H⋯O hydrogen bond, which generates an S(9) ring motif. In the crystal, pairs of C—H⋯O hydrogen bonds link centrosymmetrically related mol­ecules into dimers, generating R₂²(22) ring motifs. The crystal packing is further stabilized by C—H⋯π inter­actions.

(E)-Methyl 2-({2-eth-oxy-6-[(E)-(hy-droxy-imino)-meth-yl]phen-oxy}meth-yl)-3-phenyl-acrylate

In the title compound, C₂₀H₂₁NO₅, the dihedral angle between the mean planes through the two rings is 47.1 (8)°. The enoate group assumes an extended conformation. The hy­droxy­ethanimine group is essentially coplanar with the benzene ring, the largest deviation from the mean plane being 0.061 (1) Å for the O atom. In the crystal, mol­ecules are linked into cyclic centrosymmetric dimers with an R₂²(6) motif via pairs of O—H⋯N hydrogen bonds. Inter­molecular C—H⋯O hydrogen bonds form a C(8) chain along the b axis. The crystal packing is further stabilized by C—H⋯π inter­actions.

(E)-Methyl 3-(3,4-dimeth-oxy-phen-yl)-2-[(1,3-dioxoisoindolin-2-yl)meth-yl]acrylate

In the title compound, C(21)H(19)NO(6), the isoindole ring system is essentially planar [maximum deviation = 0.019 (2) Å for the N atom] and is oriented at a dihedral angle of 51.3 (1)° with respect to the benzene ring. The two meth-oxy groups are almost coplanar with the attached benzene ring [C-O-C-C = 3.7 (4) and 4.3 (4)°]. The mol-ecular conformation is stabilized by an intra-molecular C-H⋯O hydrogen bond, which generates an S(9) ring motif. In the crystal, mol-ecules are linked through bifurcated C-H⋯(O,O) hydrogen bonds having R(1) (2)(5) ring motifs, forming chains along the b-axis direction. The crystal packing is further stabilzed by π-π inter-actions [centriod-centroid distance = 3.463 (1) Å].

(E)-3-(2-Chlorophenyl)-2-[(2-formylphenoxy)methyl]prop-2-enenitrile

In the title compound, C17H12ClNO2, the dihedral angle between the two benzene rings is 42.9 (1)°. There are no sgnificant intermolecular interactions.

(2Z)-2-{[N-(2-Formylphenyl)-4-methylbenzenesulfonamido]methyl}-3-(4-methylphenyl)prop-2-enenitrile

In the title compound, C₂₅H₂₂N₂O₃S, the sulfonyl-bound benzene ring forms dihedral angles of 36.8 (2) and 81.4 (2)°, respectively, with the formyl­benzene and methyl­benzene rings. The mol­ecular conformation is stabilized by an intra­molecular C—H⋯O hydrogen bond, which generates an S(5) ring motif. The crystal packing is stabilized by C—H⋯O hydrogen bonds, which generate C(11) chains along the b axis. The crystal packing is further stabilized by π–π inter­actions [centroid–centroid distance = 3.927 (2) Å].

N-(2-Formyl-phen-yl)-4-toluene-sulfonamide: a second monoclinic polymorph

The title compound, C₁₄H₁₃NO₃S, (I), is a second monoclinic polymorph. The original polymorph, (II), was reported by Mahía et al. [Acta Cryst. (1999), C55, 2158–2160]. Polymorph (II) crystalllized in the space group P2₁/c (Z = 4), whereas the title polymorph (I) occurs in the space group P2₁/n (Z = 4). The dihedral angle between the two aromatic rings is 75.9 (1)° in (I) compared to 81.9 (1)° for (II). In both polymorphs, two S(6) rings are generated by intra­molecular N—H⋯O and C—H⋯O hydrogen bonds, resulting in similar mol­ecular geometries. However, the two polymorphs differ concerning their crystal packing. In (I), mol­ecules are linked into C(8) zigzag chains along the b axis by C—H⋯O hydrogen bonds, whereas in (II) mol­ecules are linked by C—H⋯O hydrogen bonds, forming C(7) chains along the b axis. The title polymorph is further stabilized by inter­molecular C—H⋯π and π–π inter­actions [centroid–centroid distance = 3.814 (1) Å]. These inter­actions are not evident in polymorph (II).