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Acta Crystallogr Sect E Struct Rep Online. 2009 January 1; 65(Pt 1): o187.
Published online 2008 December 20. doi:  10.1107/S1600536808042967
PMCID: PMC2968095

Diethyl 6H,12H-5,11-methano­dibenzo[b,f][1,5]diazo­cine-1,7-dicarboxyl­ate

Abstract

In the mol­ecule of the title compound, C21H22N2O4, the 1,7-diethyl ester analogue of Tröger’s base, the dihedral angle between the two benzene rings is 93.16 (3)°; the mol­ecule is C 2 symmetric.

Related literature

For background to the synthesis of Tröger’s base products, see: Hansson et al. (2003 [triangle]); Solano et al. (2005 [triangle]); Bhuiyan et al. (2007 [triangle]); Didier & Sergeyev (2007 [triangle]); Zhu et al. (2008 [triangle]); Vande Velde et al. (2008 [triangle]). For related structures, see: Faroughi et al. (2006 [triangle]); Bhuiyan et al. (2006 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-65-0o187-scheme1.jpg

Experimental

Crystal data

  • C21H22N2O4
  • M r = 366.41
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-65-0o187-efi1.jpg
  • a = 14.306 (3) Å
  • b = 9.251 (2) Å
  • c = 15.081 (4) Å
  • β = 118.149 (4)°
  • V = 1759.8 (7) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.10 mm−1
  • T = 150 (2) K
  • 0.47 × 0.30 × 0.19 mm

Data collection

  • Bruker SMART 1000 CCD diffractometer
  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996 [triangle]) T min = 0.856, T max = 0.980
  • 8475 measured reflections
  • 2135 independent reflections
  • 1925 reflections with I > 2σ(I)
  • R int = 0.020

Refinement

  • R[F 2 > 2σ(F 2)] = 0.036
  • wR(F 2) = 0.099
  • S = 1.04
  • 2135 reflections
  • 124 parameters
  • H-atom parameters constrained
  • Δρmax = 0.33 e Å−3
  • Δρmin = −0.19 e Å−3

Data collection: SMART (Siemens, 1995 [triangle]); cell refinement: SAINT (Siemens, 1995 [triangle]); data reduction: SAINT and XPREP (Siemens, 1995 [triangle]); program(s) used to solve structure: SIR97 (Altomare et al. 1999 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: ORTEP-3 (Farrugia, 1997 [triangle]) and WinGX32 (Farrugia, 1999 [triangle]); software used to prepare material for publication: enCIFer (Allen et al., 2004 [triangle]).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808042967/zl2169sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808042967/zl2169Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

The authors thank the Australian Research Council for a Discovery Project grant to ACT (DP0345180) and Macquarie University for the award of a Macquarie University Research Development grant to ACT and the award of an iMURS grant to MDHB.

supplementary crystallographic information

Comment

Dibenzo Tröger's base analogues are formed from the acid catalysed condensation of an aniline with either formaldehyde or formaldehyde equivalents. It was a long-held belief that a para-substituent was required on the aniline to prevent polymerization during the Tröger's base reaction and that the presence of an electron-withdrawing group would result in neglible yields of Tröger's base products. These beliefs have been proved to be incorrect, with the synthesis of tetranitro- (Bhuiyan et al., 2007) and octafluoro- (Vande Velde et al., 2008) analogues (in yields of 11% and 37%, respectively), and the synthesis of Tröger's base analogues from 2- and 3-substituted anilines lacking a substitutent in the para-position (Hansson et al., 2003), and even from aniline itself (Didier & Sergeyev, 2007). The title compound is another example of a Tröger's base analogue unsubstituted in the 2,8-positions. An important feature of all Tröger's base analogues is the V-shaped structure of the compounds. The dihedral angle between the aromatic rings has been measured for over 25 simple dibenzo Tröger's base analogues and has been found to lie between 82° (Solano et al., 2005) and 110° (Zhu et al., 2008). The X-ray structures of two related Tröger's base esters have also been reported (Faroughi et al., 2006; Bhuiyan et al., 2006). It is noteworthy that the title compound was the sole Tröger's base analogue isolated from the reaction and results from carbon-carbon bond formation at the more hindered ortho-site, relative to the aniline amino group.

The title compound, Fig. 1, crystallizes in space group C2/c and it was prepared as outlined in Fig. 2.

Experimental

Ethyl 3-aminobenzoate (2.0 g, 12.1 mmol) and paraformaldehyde (582 mg, 19.38 mmol) were dissolved in trifluoroacetic acid (75 ml) and the mixture was stirred under an argon atmosphere in the dark 7 days. The reaction mixture was then basified with a solution of concentrated ammonia (80 ml) in water (120 ml). A saturated sodium hydrogen carbonate solution (100 ml) was added and the crude material was extracted into ethyl acetate (3 × 75 ml). The combined organic layers were washed with brine (100 ml), dried over anhydrous sodium sulfate, filtered and evaporated to dryness to yield an orange solid. The crude material was purified by recrystallization from hexane to afford the title compound (760 mg, 34%) as a white solid and a racemic mixture, m.p. 441–443 K.

Single crystals of the title compound were produced by slow evaporation of a dichloromethane solution.

Refinement

C-bound H atoms were included in idealized positions and refined using a riding model. Methylene, aromatic and methyl C—H bond lengths were fixed at 0.99, 0.95 and 0.98 Å, respectively. Uiso(H) values were fixed at 1.2Ueq(C) for methylene and aromatic H atoms, and at 1.5Ueq(C) for methyl H atoms.

Figures

Fig. 1.
View of the title compound, showing the atomic numbering scheme. Displacement ellipsoids are shown at the 50% probability level. Symmetry code used to generate equivalent atoms: 2-x, y, 1.5-z.
Fig. 2.
Synthetic scheme for the synthesis of the title compound showing the numbering system used in naming the compound.

Crystal data

C21H22N2O4F(000) = 776
Mr = 366.41Dx = 1.383 Mg m3
Monoclinic, C2/cMelting point: 441 K
Hall symbol: -C 2ycMo Kα radiation, λ = 0.71073 Å
a = 14.306 (3) ÅCell parameters from 5209 reflections
b = 9.251 (2) Åθ = 2.7–28.5°
c = 15.081 (4) ŵ = 0.10 mm1
β = 118.149 (4)°T = 150 K
V = 1759.8 (7) Å3Shard, colourless
Z = 40.47 × 0.30 × 0.19 mm

Data collection

Bruker SMART 1000 CCD diffractometer2135 independent reflections
Radiation source: sealed tube1925 reflections with I > 2σ(I)
graphiteRint = 0.020
ω scansθmax = 28.5°, θmin = 2.7°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)h = −19→19
Tmin = 0.856, Tmax = 0.980k = −12→11
8475 measured reflectionsl = −20→20

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.036Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.099H-atom parameters constrained
S = 1.04w = 1/[σ2(Fo2) + (0.0513P)2 + 1.146P] where P = (Fo2 + 2Fc2)/3
2135 reflections(Δ/σ)max = 0.001
124 parametersΔρmax = 0.33 e Å3
0 restraintsΔρmin = −0.18 e Å3

Special details

Experimental. The crystal was coated in Exxon Paratone N hydrocarbon oil and mounted on a thin mohair fibre attached to a copper pin. Upon mounting on the diffractometer, the crystal was quenched to 150(K) under a cold nitrogen gas stream supplied by an Oxford Cryosystems Cryostream and data were collected at this temperature.
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

xyzUiso*/UeqOcc. (<1)
C10.83967 (10)0.37215 (14)1.11492 (10)0.0346 (3)
H1A0.76690.40241.06920.052*
H1B0.85630.39441.18440.052*
H1C0.84650.26791.10810.052*
C20.91539 (9)0.45165 (12)1.08889 (8)0.0291 (2)
H2A0.91250.55641.10070.035*
H2B0.98860.41771.13280.035*
C30.92507 (8)0.30443 (11)0.96454 (8)0.0217 (2)
C40.88028 (8)0.27735 (11)0.85453 (8)0.0205 (2)
C50.92893 (8)0.17644 (10)0.81900 (8)0.0194 (2)
C60.87857 (8)0.14597 (11)0.71558 (8)0.0201 (2)
C70.78414 (8)0.21655 (12)0.65048 (8)0.0238 (2)
H70.75030.19410.58080.029*
C80.73945 (8)0.31834 (12)0.68617 (8)0.0262 (2)
H80.67640.36730.64110.031*
C90.78727 (8)0.34861 (12)0.78832 (8)0.0242 (2)
H90.75660.41800.81330.029*
C101.03523 (8)0.10512 (11)0.88716 (8)0.0211 (2)
H10A1.08460.17830.93350.025*
H10B1.02500.02940.92820.025*
C111.0000−0.05009 (15)0.75000.0236 (3)
H11A0.9674−0.11290.78100.028*0.50
H11B1.0326−0.11290.71900.028*0.50
N10.91816 (7)0.03970 (9)0.67236 (6)0.0214 (2)
O10.88792 (6)0.42718 (8)0.98415 (6)0.02669 (19)
O20.98621 (6)0.22448 (9)1.02960 (6)0.0285 (2)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
C10.0422 (7)0.0347 (6)0.0350 (6)−0.0024 (5)0.0249 (5)−0.0045 (5)
C20.0339 (6)0.0266 (5)0.0284 (5)−0.0023 (4)0.0161 (5)−0.0066 (4)
C30.0205 (5)0.0209 (5)0.0272 (5)−0.0007 (4)0.0142 (4)0.0015 (4)
C40.0195 (5)0.0198 (5)0.0247 (5)−0.0003 (4)0.0124 (4)0.0025 (4)
C50.0178 (4)0.0174 (4)0.0246 (5)−0.0002 (3)0.0113 (4)0.0032 (4)
C60.0186 (4)0.0182 (4)0.0256 (5)−0.0032 (4)0.0121 (4)0.0005 (4)
C70.0192 (5)0.0274 (5)0.0234 (5)−0.0028 (4)0.0090 (4)0.0014 (4)
C80.0182 (5)0.0294 (5)0.0293 (5)0.0037 (4)0.0097 (4)0.0062 (4)
C90.0210 (5)0.0240 (5)0.0305 (5)0.0039 (4)0.0146 (4)0.0033 (4)
C100.0208 (5)0.0206 (5)0.0230 (5)0.0031 (4)0.0113 (4)0.0027 (4)
C110.0254 (7)0.0177 (6)0.0296 (7)0.0000.0145 (6)0.000
N10.0215 (4)0.0191 (4)0.0257 (4)−0.0021 (3)0.0128 (4)−0.0009 (3)
O10.0322 (4)0.0230 (4)0.0277 (4)0.0043 (3)0.0165 (3)0.0007 (3)
O20.0307 (4)0.0292 (4)0.0258 (4)0.0078 (3)0.0135 (3)0.0048 (3)

Geometric parameters (Å, °)

C1—C21.5065 (17)C6—C71.4014 (14)
C1—H1A0.9800C6—N11.4354 (13)
C1—H1B0.9800C7—C81.3820 (16)
C1—H1C0.9800C7—H70.9500
C2—O11.4544 (13)C8—C91.3876 (16)
C2—H2A0.9900C8—H80.9500
C2—H2B0.9900C9—H90.9500
C3—O21.2103 (13)C10—N1i1.4770 (13)
C3—O11.3445 (13)C10—H10A0.9900
C3—C41.4909 (15)C10—H10B0.9900
C4—C91.3959 (14)C11—N11.4623 (12)
C4—C51.4124 (14)C11—H11A0.9900
C5—C61.4039 (15)C11—H11B0.9900
C5—C101.5262 (13)
C2—C1—H1A109.5C8—C7—H7119.5
C2—C1—H1B109.5C6—C7—H7119.5
H1A—C1—H1B109.5C7—C8—C9119.58 (10)
C2—C1—H1C109.5C7—C8—H8120.2
H1A—C1—H1C109.5C9—C8—H8120.2
H1B—C1—H1C109.5C8—C9—C4120.20 (10)
O1—C2—C1110.36 (9)C8—C9—H9119.9
O1—C2—H2A109.6C4—C9—H9119.9
C1—C2—H2A109.6N1i—C10—C5111.09 (8)
O1—C2—H2B109.6N1i—C10—H10A109.4
C1—C2—H2B109.6C5—C10—H10A109.4
H2A—C2—H2B108.1N1i—C10—H10B109.4
O2—C3—O1123.18 (10)C5—C10—H10B109.4
O2—C3—C4124.49 (10)H10A—C10—H10B108.0
O1—C3—C4112.31 (9)N1i—C11—N1110.77 (11)
C9—C4—C5120.99 (10)N1i—C11—H11A109.5
C9—C4—C3118.74 (9)N1—C11—H11A109.5
C5—C4—C3120.21 (9)N1i—C11—H11B109.5
C6—C5—C4117.88 (9)N1—C11—H11B109.5
C6—C5—C10119.18 (9)H11A—C11—H11B108.1
C4—C5—C10122.88 (9)C6—N1—C11111.33 (8)
C7—C6—C5120.31 (9)C6—N1—C10i112.54 (8)
C7—C6—N1117.22 (9)C11—N1—C10i107.39 (7)
C5—C6—N1122.43 (9)C3—O1—C2115.98 (8)
C8—C7—C6120.98 (10)
O2—C3—C4—C9159.42 (10)C7—C8—C9—C40.40 (16)
O1—C3—C4—C9−19.11 (13)C5—C4—C9—C81.66 (16)
O2—C3—C4—C5−17.78 (16)C3—C4—C9—C8−175.52 (10)
O1—C3—C4—C5163.70 (9)C6—C5—C10—N1i13.93 (12)
C9—C4—C5—C6−2.43 (14)C4—C5—C10—N1i−163.33 (9)
C3—C4—C5—C6174.70 (9)C7—C6—N1—C11−165.60 (8)
C9—C4—C5—C10174.85 (9)C5—C6—N1—C1112.31 (12)
C3—C4—C5—C10−8.01 (14)C7—C6—N1—C10i73.76 (11)
C4—C5—C6—C71.21 (14)C5—C6—N1—C10i−108.32 (10)
C10—C5—C6—C7−176.18 (9)N1i—C11—N1—C6−51.41 (6)
C4—C5—C6—N1−176.64 (8)N1i—C11—N1—C10i72.21 (6)
C10—C5—C6—N15.97 (14)O2—C3—O1—C2−7.03 (15)
C5—C6—C7—C80.80 (15)C4—C3—O1—C2171.51 (8)
N1—C6—C7—C8178.76 (9)C1—C2—O1—C3−83.19 (12)
C6—C7—C8—C9−1.62 (16)

Symmetry codes: (i) −x+2, y, −z+3/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: ZL2169).

References

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