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Acta Crystallogr C. 2009 September 15; 65(Pt 9): o465–o469.
Published online 2009 August 19. doi:  10.1107/S0108270109030339
PMCID: PMC2737425

Four differently substituted 2-aryl-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepines: hydrogen-bonded structures in one, two and three dimensions

Abstract

In (2RS,4SR)-7-chloro-2-exo-(2-chloro-6-fluoro­phen­yl)-2,3,4,5-tetra­hydro-1H-1,4-epoxy-1-benzazepine, C16H12Cl2FNO, (I), mol­ecules are linked into chains by a single C—H(...)π(arene) hydrogen bond. (2RS,4SR)-2-exo-(2-Chloro-6-fluoro­phen­yl)-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepine, C16H13ClFNO, (II), is isomorphous with compound (I) but not strictly isostructural with it, as the hydrogen-bonded chains in (II) are linked into sheets by an aromatic π–π stacking inter­action. The mol­ecules of (2RS,4SR)-7-methyl-2-exo-(4-methyl­phenyl)-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepine, C18H19NO, (III), are linked into sheets by a combination of C—H(...)N and C—H(...)π(arene) hydrogen bonds. (2S,4R)-2-exo-(2-Chloro­phen­yl)-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepine, C16H14ClNO, (IV), crystallizes as a single enantiomer and the mol­ecules are linked into a three-dimensional framework structure by a combination of one C—H(...)O hydrogen bond and three C—H(...)π(arene) hydrogen bonds.

Comment

We report here the structures of four new substituted 2-aryl-1,4-epoxy­tetra­hydro-1-benzazepines, namely (2RS,4SR)-7-chloro-2-exo-(2-chloro-6-fluoro­phen­yl)-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepine, (I), (2RS,4SR)-2-exo-(2-chloro-6-fluoro­phen­yl)-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepine, (II), (2RS,4SR)-7-methyl-2-exo-(4-methyl­phen­yl)-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepine, (III), and (2S,4R)-2-exo-(2-chloro­phen­yl)-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepine, (IV) (Fig. 1 [triangle]). The work reported here is a continuation of our structural study (Acosta et al., 2008 [triangle]; Blanco et al., 2008 [triangle]; Gómez et al., 2008 [triangle]) of 2-substituted 1,4-epoxy­tetra­hydro-1-benzazepines, which included two close analogues of the present compounds, namely compounds (V) and (VI). Compounds (I)–(IV) were all synthesized using our previously reported synthetic approach (Gómez Ayala et al., 2006 [triangle]), with the eventual aim of identifying structurally novel anti­parasitic compounds which are active against Trypanosoma cruzi and Leishmania chagasi parasites (Palma et al., 2009 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-scheme1.jpg

Figure 1
The mol­ecular structures of (a) compound (I), (b) compound (II), (c) compound (III) and (d) compound (IV), shown as the (2S,4R) form in each case. Displacement ellipsoids are drawn at the 30% probability level.

Compounds (I)–(III) all crystallize as racemates, while the crystals of (IV) contain only a single enanti­omer, viz. (2S,4R), in the crystal selected for data collection. Given the racemic nature of (I)–(III) and the absence of any reagent in the synthetic procedure likely to be able to provide enanti­omeric selectivity, it seems probable that (IV) is, in fact, produced as a mixture of (2S,4R) and (2R,4S) enanti­omers, but that it happens to crystallize as a conglomerate rather than as a racemate. In this connection, it is inter­esting to note that, while (V) crystallizes as a racemate in the space group Pna21, (VI) crystallizes as a single enanti­omer in the space group P212121 (Gómez et al., 2008 [triangle]).

Compounds (I) and (II), which differ only in the presence of the 7-chloro substituent in (I), are isomorphous, with similar unit-cell dimensions and similar atomic coordinates for the corresponding atoms. However, they are not strictly isostructural (Acosta et al., 2009 [triangle]), as the direction-specific inter­molecular inter­actions in the two crystal structures are subtly different, as discussed below. Although pairs of analogous compounds carrying, respectively, a methyl or a chloro substituent at equivalent sites are not infrequently isomorphous, no such relationship is evident for (III) and (V), which crystallize, respectively, in the space groups P21/n and Pna21 and which exhibit entirely different modes of supra­molecular aggregation.

The ring-puckering parameters (Cremer & Pople, 1975 [triangle]) for (I)–(IV) are collected in Table 1 [triangle], along with those for (V) and (VI) (Gómez et al., 2008 [triangle]) for comparison. All six compounds exhibit very similar shapes for the fused heterocyclic ring system. The five-membered ring component in each of (I), (II), (V) and (VI) adopts a nearly perfect half-chair conformation, for which the idealized value of the puckering angle ϕ is (36k + 18)°, where k represents an integer; the conformations in (III) and (IV) are inter­mediate between half-chair and envelope forms, for which the idealized value of ϕ is 36k°. The six-membered ring components all adopt conformations closer to the half-chair form, for which the ideal values of the ring-puckering angles are θ = 50.8° and ϕ = (60k + 30)°, than to the envelope conformation, where the ideal values of the puckering angles are θ = 54.7° and ϕ = 60k°.

Table 1
Ring-puckering parameters (Å, °) for compounds (I)–(VI)

The supra­molecular aggregation in (I)–(IV) is dominated by C—H(...)O, C—H(...)N and C—H(...)π(arene) hydrogen bonds, augmented by aromatic π–π stacking inter­actions in (II) only. There are short inter­molecular C—H(...)F contacts in (I) and (II) and an inter­molecular C—H(...)Cl contact in (IV). None of these contacts is likely to be of structural significance, firstly because the C—H bonds involved are of low acidity, and secondly because it has been well established that F and Cl atoms when bound to C atoms are extremely poor acceptors of hydrogen bonds, even from donors such as O or N (Aakeröy et al., 1999 [triangle]; Brammer et al., 2001 [triangle]; Howard et al., 1996 [triangle]; Thallapally & Nangia, 2001 [triangle]). Similarly, in the inter­molecular C—H(...)N contacts in (I) and (II), involving a C—H bond of low acidity, the H(...)N distances are probably too long for these contacts to be of structural significance.

On this basis, the mol­ecules of (I) are linked by just a single C—H(...)π(arene) hydrogen bond (Table 2 [triangle]) to form a simple chain running parallel to the [10An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi1.jpg] direction (Fig. 2 [triangle]), with no direction-specific inter­actions between adjacent chains. Entirely analogous chains are formed in (II), but these chains are now linked into sheets by a π–π stacking inter­action. The fused aryl rings in the mol­ecules at (x, y, z) and (1 − x, 1 − y, −z) are strictly parallel, with an inter­planar spacing of 3.426 (2) Å, a ring-centroid separation of 3.810 (2) Å and a ring-centroid offset of 1.667 (2) Å. The effect of this inter­action is to link the chains parallel to [10An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi1.jpg] into a sheet lying parallel to (101) (Fig. 3 [triangle]).

Figure 2
A stereoview of part of the crystal structure of (I), showing the formation of a hydrogen-bonded chain running parallel to the [10An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi1.jpg] direction. For the sake of clarity, H atoms not involved in the motif shown have been omitted.
Figure 3
A stereoview of part of the crystal structure of (II), showing the formation of a sheet parallel to (101) built from the π-stacking of hydrogen-bonded chains parallel to [10An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi1.jpg]. For the sake of clarity, H atoms not involved in the motif shown have ...
Table 2
Hydrogen bonds and short intermolecular contacts (Å, °) for compounds (I)–(IV)

The crystal structure of (III) also contains sheets, but these are built solely from two hydrogen bonds, one each of the C—H(...)N and C—H(...)π(arene) types (Table 2 [triangle]). The C—H(...)π(arene) inter­action links a pair of mol­ecules into a cyclic centrosymmetric dimer centred at (An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi3.jpg, 1, 0), and this dimer can be regarded as the building block for the sheet formation. The C—H(...)N hydrogen bond links the reference dimer centred at (An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi3.jpg, 1, 0) directly to four other such dimers, viz. those centred at (0, An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi3.jpg, −An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi3.jpg), (0, An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi7.jpg, −An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi3.jpg), (1, An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi3.jpg, An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi3.jpg) and (1, An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi7.jpg, An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi3.jpg), and propagation of these two inter­actions then generates a hydrogen-bonded sheet lying parallel to (10An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi1.jpg) (Fig. 4 [triangle]).

Figure 4
A stereoview of part of the crystal structure of (III), showing the formation of a hydrogen-bonded sheet parallel to (10An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi1.jpg) built from C—H(...)N and C—H(...)π(arene) hydrogen bonds. For the sake of clarity, H atoms bonded ...

Four hydrogen bonds, one of the C—H(...)O type and three of the C—H(...)π(arene) type, combine to link the mol­ecules of (IV) into a single three-dimensional framework. The formation of the framework is most readily analysed in terms of two independent two-dimensional substructures. The three hydrogen bonds involving atoms C4, C6 and C8 as the donors combine to generate a sheet lying parallel to (001) (Fig. 5 [triangle]), while the two hydrogen bonds having C4 and C23 as the donors combine to form a sheet parallel to (100) (Fig. 6 [triangle]). The combination of the (100) and (001) sheets is sufficient to generate a three-dimensional structure.

Figure 5
A stereoview of part of the crystal structure of (IV), showing the formation of a hydrogen-bonded sheet parallel to (001) built from one C—H(...)O and two C—H(...)π(arene) hydrogen bonds. For the sake of clarity, H atoms ...
Figure 6
A stereoview of part of the crystal structure of (IV), showing the formation of a hydrogen-bonded sheet parallel to (100) built from one C—H(...)O and one C—H(...)π(arene) hydrogen bond. For the sake of clarity, H atoms ...

It is of inter­est briefly to compare the aggregation in (I)–(IV) with that in the related compounds (V) and (VI) (Gómez et al., 2008 [triangle]). In (V), the mol­ecules are linked by a combination of C—H(...)O and C—H(...)N hydrogen bonds to form a chain of edge-fused An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi14.jpg(12) (Bernstein et al., 1995 [triangle]) rings, while in (VI), a combination of two C—H(...)O hydrogen bonds and one C—H(...)π(arene) hydrogen bond generates a three-dimensional framework structure. In the course of the present work, we have also investigated (VII), which crystallizes in the space group P An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi1.jpg with Z′ = 2, but we have been unable to refine this below R = 0.11. However, it is clear that the two independent mol­ecules within the asymmetric unit are linked by one C—H(...)O hydrogen bond and one C—H(...)N hydrogen bond to form an An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi16.jpg(8) motif, but that there are no further direction-specific inter­actions between the mol­ecules. Thus, despite the very close constitutional, configurational and conformational similarity between the mol­ecules of compounds (I)–(VII), no two of these compounds exhibits the same pattern of supra­molecular aggregation.

Experimental

For the preparation of compounds (I)–(IV), sodium tungstate dihydrate, Na2WO4·2H2O (10 mol%), followed by 30% aqueous hydrogen peroxide solution (added dropwise, 0.30 mol) were added to a stirred solution of the appropriately substituted 2-allyl-N-benzyl­aniline (0.10 mol) in methanol (34 ml) for (I), (III) and (IV), or in a mixture of methanol (34 ml) and nitro­methane (3.4 ml) for (II). The resulting mixtures were then stirred at ambient temperature for periods ranging from 30 to 100 h. Each mixture was filtered and the solvent removed under reduced pressure. Toluene (40 ml) for compounds (I), (III) and (IV) or ethyl acetate (40 ml) for (II) was added to the solid residue and the resulting solution was heated to ca 353 K for periods ranging from 6 to 8 h. After cooling each solution to ambient temperature, the solvent was removed under reduced pressure and the crude products were purified by chromatography on silica gel using heptane–ethyl acetate (compositions ranged from 90:1 to 60:1 v/v) as eluant. Crystallization from heptane gave colourless crystals suitable for single-crystal X-ray diffraction. For (I), m.p. 429–430 K, yield 50%; MS (70 eV) m/z (%): 323 (M +, 35Cl, 17), 306 (3), 294 (1), 280 (1), 164 (3), 138 (100), 125 (6), 111 (4). For (II), m.p. 433–434 K, yield 65%; MS (70 eV) m/z (%): 289 (M +, 35Cl, 32), 272 (7), 260 (1), 246 (3), 130 (4), 104 (100), 91 (10), 77 (10). For (III), m.p. 374–376 K, yield 45%; MS (70 eV) m/z (%): 265 (M +, 35), 248 (18), 222 (10), 207 (5), 146 (7), 132 (23), 118 (100), 103 (12), 91 (30), 77 (18), 65 (9), 51 (5). For (IV), m.p. 385–387 K, yield 63%; MS (70 eV) m/z (%): 271 (M +, 35Cl, 50), 254 (19), 242 (2), 228 (2), 130 (4), 104 (100), 91 (25), 77 (26).

Compound (I)

Crystal data

  • C16H12Cl2FNO
  • M r = 324.17
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi17.jpg
  • a = 9.2907 (11) Å
  • b = 10.8720 (9) Å
  • c = 13.4523 (13) Å
  • β = 95.964 (8)°
  • V = 1351.4 (2) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.49 mm−1
  • T = 120 K
  • 0.35 × 0.06 × 0.06 mm

Data collection

  • Bruker–Nonius KappaCCD diffractometer
  • Absorption correction: multi-scan (SADABS; Sheldrick, 2003 [triangle]) T min = 0.868, T max = 0.971
  • 19650 measured reflections
  • 3105 independent reflections
  • 1774 reflections with I > 2σ(I)
  • R int = 0.103

Refinement

  • R[F 2 > 2σ(F 2)] = 0.049
  • wR(F 2) = 0.121
  • S = 1.07
  • 3105 reflections
  • 190 parameters
  • H-atom parameters constrained
  • Δρmax = 0.38 e Å−3
  • Δρmin = −0.44 e Å−3

Compound (II)

Crystal data

  • C16H13ClFNO
  • M r = 289.72
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi17.jpg
  • a = 9.0768 (13) Å
  • b = 10.9461 (9) Å
  • c = 12.9971 (18) Å
  • β = 99.768 (9)°
  • V = 1272.6 (3) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.31 mm−1
  • T = 120 K
  • 0.32 × 0.27 × 0.22 mm

Data collection

  • Bruker–Nonius KappaCCD diffractometer
  • Absorption correction: multi-scan (SADABS; Sheldrick, 2003 [triangle]) T min = 0.894, T max = 0.936
  • 18555 measured reflections
  • 2918 independent reflections
  • 2085 reflections with I > 2σ(I)
  • R int = 0.055

Refinement

  • R[F 2 > 2σ(F 2)] = 0.047
  • wR(F 2) = 0.137
  • S = 1.04
  • 2918 reflections
  • 181 parameters
  • H-atom parameters constrained
  • Δρmax = 0.29 e Å−3
  • Δρmin = −0.37 e Å−3

Compound (III)

Crystal data

  • C18H19NO
  • M r = 265.34
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi17.jpg
  • a = 9.7687 (9) Å
  • b = 10.3022 (17) Å
  • c = 14.239 (2) Å
  • β = 108.222 (10)°
  • V = 1361.1 (3) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.08 mm−1
  • T = 120 K
  • 0.33 × 0.27 × 0.12 mm

Data collection

  • Bruker–Nonius KappaCCD diffractometer
  • Absorption correction: multi-scan (SADABS; Sheldrick, 2003 [triangle]) T min = 0.962, T max = 0.991
  • 20555 measured reflections
  • 3133 independent reflections
  • 1788 reflections with I > 2σ(I)
  • R int = 0.096

Refinement

  • R[F 2 > 2σ(F 2)] = 0.063
  • wR(F 2) = 0.135
  • S = 1.08
  • 3133 reflections
  • 183 parameters
  • H-atom parameters constrained
  • Δρmax = 0.27 e Å−3
  • Δρmin = −0.26 e Å−3

Compound (IV)

Crystal data

  • C16H14ClNO
  • M r = 271.73
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is c-65-0o465-efi20.jpg
  • a = 8.8558 (19) Å
  • b = 7.3585 (13) Å
  • c = 9.9622 (18) Å
  • β = 101.622 (17)°
  • V = 635.9 (2) Å3
  • Z = 2
  • Mo Kα radiation
  • μ = 0.29 mm−1
  • T = 120 K
  • 0.25 × 0.15 × 0.07 mm

Data collection

  • Bruker–Nonius KappaCCD diffractometer
  • Absorption correction: multi-scan (SADABS; Sheldrick, 2003 [triangle]) T min = 0.919, T max = 0.980
  • 10226 measured reflections
  • 2889 independent reflections
  • 2400 reflections with I > 2σ(I)
  • R int = 0.048

Refinement

  • R[F 2 > 2σ(F 2)] = 0.038
  • wR(F 2) = 0.078
  • S = 1.08
  • 2889 reflections
  • 172 parameters
  • 1 restraint
  • H-atom parameters constrained
  • Δρmax = 0.23 e Å−3
  • Δρmin = −0.22 e Å−3
  • Absolute structure: Flack (1983 [triangle]), 1323 Bijvoet pairs
  • Flack parameter: 0.07 (6)

All H atoms were located in difference maps and then treated as riding atoms in geometrically idealized positions, with C—H distances of 0.95 (aromatic), 0.98 (CH3), 0.99 (CH2) or 1.00 Å (aliphatic CH), and with U iso(H) = kU eq(C), where k = 1.5 for the methyl groups, which were permitted to rotate but not to tilt, and k = 1.2 for all other H atoms. For (IV), the absolute configuration of the mol­ecules in the crystal selected for data collection was established as (2S,4R) by means of the Flack (1983 [triangle]) x parameter of 0.07 (6) and the Hooft y parameter (Hooft et al., 2008 [triangle]) of 0.03 (4). Accordingly, the configuration of the reference mol­ecules in the racemic compounds (I)–(III) was set to be S at C2, and on this basis all three compounds have configuration R at C4 for the reference mol­ecules, so that the overall configuration for each of (I)–(III) is (2SR,4RS).

For all compounds, data collection: COLLECT (Hooft, 1999 [triangle]); cell refinement: DIRAX/LSQ (Duisenberg et al., 2000 [triangle]); data reduction: EVALCCD (Duisenberg et al., 2003 [triangle]); program(s) used to solve structure: SIR2004 (Burla et al., 2005 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: PLATON (Spek, 2009 [triangle]); software used to prepare material for publication: SHELXL97 and PLATON.

Supplementary Material

Crystal structure: contains datablocks global, I, II, III, IV, VII. DOI: 10.1107/S0108270109030339/fa3200sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S0108270109030339/fa3200Isup2.hkl

Structure factors: contains datablocks II. DOI: 10.1107/S0108270109030339/fa3200IIsup3.hkl

Structure factors: contains datablocks III. DOI: 10.1107/S0108270109030339/fa3200IIIsup4.hkl

Structure factors: contains datablocks IV. DOI: 10.1107/S0108270109030339/fa3200IVsup5.hkl

Acknowledgments

The authors thank ‘Servicios Técnicos de Investigación of Universidad de Jaén’ and the staff for data collection. JC thanks the Consejería de Innovación, Ciencia y Empresa (Junta de Andalucía, Spain), the Universidad de Jaén (project reference UJA_07_16_33) and Ministerio de Ciencia e Innovación (project reference SAF2008-04685-C02-02) for financial support. AP, SLG and CMS thanks COLCIENCIAS for financial support (grant No. 1102-408-20563).

Footnotes

Supplementary data for this paper are available from the IUCr electronic archives (Reference: FA3200). Services for accessing these data are described at the back of the journal.

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Articles from Acta Crystallographica Section C: Crystal Structure Communications are provided here courtesy of International Union of Crystallography