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Acta Crystallogr Sect E Struct Rep Online. 2008 November 1; 64(Pt 11): o2156.
Published online 2008 October 22. doi:  10.1107/S1600536808033850
PMCID: PMC2959763

2,2,9-Trimethyl-2,3-dihydro­pyrano[2,3-a]carbazol-4-(11H)-one

Abstract

The title compound, C18H17NO2, was prepared from 1-hydr­oxy-7-methyl­carbazole and 3,3-dimethyl­acrylic acid with trifluoro­acetic acid as the cyclization catalyst. The mol­ecules contain an essentially planar 6-methyl­indole unit. The second aromatic ring is significantly bent away from the plane of this unit, with maximum deviations of 0.171 (1) and 0.185 (1) Å for two of the C atoms. In the crystal structure, there are neither N—H(...)O hydrogen bonds nor π–π stacking between the aromatic sections of neighboring mol­ecules. There is only one weak C—H(...)O hydrogen bond and a number of weak C—H(...)π inter­actions.

Related literature

Knölker & Reddy (2002 [triangle]) report on the isolation of pyran­o­carbazoles from various plant species. Sridharan et al. (2007 [triangle]) describe the synthesis of compounds related to the title compound. Sridharan et al. (2008a [triangle],b [triangle]) report the structures of the 9-H and 10-methyl derivatives of the title compound.

An external file that holds a picture, illustration, etc.
Object name is e-64-o2156-scheme1.jpg

Experimental

Crystal data

  • C18H17NO2
  • M r = 279.33
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-64-o2156-efi1.jpg
  • a = 8.6702 (7) Å
  • b = 6.1647 (5) Å
  • c = 26.617 (2) Å
  • β = 99.100 (1)°
  • V = 1404.7 (2) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.09 mm−1
  • T = 100 (2) K
  • 0.57 × 0.48 × 0.24 mm

Data collection

  • Bruker APEXII CCD diffractometer
  • Absorption correction: multi-scan (SADABS; Bruker, 2007 [triangle]) T min = 0.883, T max = 0.980
  • 12327 measured reflections
  • 3044 independent reflections
  • 2708 reflections with I > 2σ(I)
  • R int = 0.031

Refinement

  • R[F 2 > 2σ(F 2)] = 0.039
  • wR(F 2) = 0.098
  • S = 1.04
  • 3044 reflections
  • 193 parameters
  • H-atom parameters constrained
  • Δρmax = 0.27 e Å−3
  • Δρmin = −0.21 e Å−3

Data collection: APEX2 (Bruker, 2007 [triangle]); cell refinement: SAINT (Bruker, 2007 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXTL; molecular graphics: Mercury (Macrae et al., 2006 [triangle]); software used to prepare material for publication: SHELXTL.

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808033850/hb2804sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808033850/hb2804Isup2.hkl

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

Acknowledgments

The authors acknowledge UGC, New Delhi, India, for the award of Major Research Project (grant No. F31-122/2005). MS thanks UGC, New Delhi, India, for the award of a research fellowship. The diffractometer was funded by the NSF (grant No. 0087210), the Ohio Board of Regents (grant No. CAP-491) and by YSU.

supplementary crystallographic information

Comment

Carbazole alkaloids have been isolated from the taxonomically related higher plants of the genus Murraya, Glycosmis, and Clausena from the family Rutaceae. Among the carbazole alkaloids pyranocarbazole alkaloids play a very important role. In this class girinimbine was the first member of the pyrano[3,2-a]carbazole alkaloid family to be isolated from M. Koenigii Spreng (Knölker & Reddy, 2002, and references therein). The isolation of these classes of compounds became an active area of study since these compounds possess high levels of biological and pharmacological activity. Hence we attempted to synthesize pyranocarbazoles by a simple and efficient route.

Using trifluoroacetic acid as the acylating agent we had been able to synthezize in high yields a range of pyranocarbazolones and we recently reported (Sridharan et al., 2007) the synthesis and crystallographic behaviour of 2,3-dihydro-2,2,8-trimethylpyrano[2,3-a]carbazol-4-(11H)-one. As an extension of this reasearch, and to further proof the credibility of trifluoroacetic acid as a good acylating agent, we further extended this synthetic route with a series of substituted 1-hydroxycarbazoles. The components thus synthesized were used as starting synthons to develop routes towards substituted pyranocarbazole derivatives. Herein we report the crystal structures of the title compound, (I).

The molecules in (I) consist of an essential planar 6-methyl-indole unit made up of the atoms C1 to C7, C12 and N1. Also in plane with this unit are the atoms C8, C11 and O1, and the overall r.m.s. deviation from planarity for these atoms is 0.0319 Å. In the structures of two related compounds (Sridharan et al., 2008a and 2008b) differentiated from the title compound only by the presence and/or position of one methyl group, the molecules were essentially planar with the only exception being the atoms of the C(CH3)2 unit of the pyranone rings. For the title compound, however, the remainder of the molecule, including the atoms C9 and C10 of the second aromatic six membered ring, are all deviating from the plane formed by the indole subunit. The aromatic ring is signifcantely bent away from this plane with C9 and C10 being displaced by 0.171 (1) and 0.185 (1) Å, respectively.

Differences between (I) and the two related structures (Sridharan et al., 2008a and 2008b) extend into the crystal packing as well. The other compounds are dominated by strong N—H···O hydrogen bonds and also exhibit a range of π–π stacking as well as weak C—H···O interactions. The title compound, however, while only being differentiated from the other two molecules by the presence and/or position of one methyl group, does not exhibit any strong N—H···O hydrogen bonds and it also does not exhibit any π–π stacking between the aromatic sections of neighboring molecules. There is only one weak C—H···O hydrogen bond (Table 1). Other intermolecular interactions are limited to even weaker C—H···π interactions (Table 1, Figure 3). Centroids given in Table 1 are defined as follows: Cg1: the pyrrol ring (N1, C1, C6, C7, C12); Cg2: C1 to C6; Cg3: C7 to C12

In the absence of stronger interactions the large number of these contacts dominates the packing forces. Molecules within the unit cell are rougly aligned along the long axis of the unit cell (the c axis) and neighboring molecules are twisted against each other so that their planes are approximately perpendicular to each other, thus allowing the C—H···π interactions to establish themselves as shown in Figure 3. Each molecule is both C—H donor towards two neighboring molecules and C—H acceptor for two other neighbors. In combination this creates layers of molecules connected by C—H···π interactions. Each layer is in turn connected with parallel layers by weak C—H···O hydrogen bonds as shown in Figure 4.

Experimental

1-hydroxy-7-methylcarbazole (0.001 mol) dissolved in 10 ml of trifluoroaceticacid was heated with 3,3-dimethylacrylicacid (0.001 mol) at 323 K for 5 h. The reaction was monitored by TLC. After completion of the reaction, the excess trifluroaceticacid was removed using rotary evaporation. The solid that precipitated out was poured onto ice water, then extracted using ethyl acetate and dried over anhydrous sodium sulfate and filtered. Then the solvent was removed under vacuum and the residue was purified by column chromatography on silica gel using petroleum ether/ ethyl acetate (95:5 v/v) as the eluant. Evaporation of solvent afforded yellow crystals which were recrystallized from ethanol to yield yellow blocks of (I) (0.262 g, 94%), m.p. 463–465 K.

Refinement

All hydrogen atoms were added in calculated positions with C—H bond distances of 0.99 (methylene), 0.95 (aromatic) and 0.98 Å (methyl) and an N—H distance of 0.88 Å. They were refined as riding with Uiso(H) = 1.2Ueq(C,N) or 1.5Ueq(methyl C).

Figures

Fig. 1.
Reaction sequence
Fig. 2.
The molecular structure of (I) showing xx% displacement ellipsoids. H atoms are represented in stick mode.
Fig. 3.
Packing view of (I) showing part of one of the layers held together by C—H···π interactions. Blue dashed lines indicate short N/C—H···C contacts, green dashed lines indicate N/C—H ...
Fig. 4.
Packing view showing two of the layers held together by C—H···π interactions and the C—H···O hydrogen bonds between the layers. Blue dashed lines indicate short C—H···O ...

Crystal data

C18H17NO2F(000) = 592
Mr = 279.33Dx = 1.321 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 5407 reflections
a = 8.6702 (7) Åθ = 2.4–27.0°
b = 6.1647 (5) ŵ = 0.09 mm1
c = 26.617 (2) ÅT = 100 K
β = 99.100 (1)°Block, yellow
V = 1404.7 (2) Å30.57 × 0.48 × 0.24 mm
Z = 4

Data collection

Bruker APEXII CCD diffractometer3044 independent reflections
Radiation source: fine-focus sealed tube2708 reflections with I > 2σ(I)
graphiteRint = 0.031
ω scansθmax = 27.0°, θmin = 2.4°
Absorption correction: multi-scan (SADABS; Bruker, 2007)h = −10→11
Tmin = 0.883, Tmax = 0.980k = −7→7
12327 measured reflectionsl = −33→33

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)] = 0.039Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.098H-atom parameters constrained
S = 1.04w = 1/[σ2(Fo2) + (0.0431P)2 + 0.5637P] where P = (Fo2 + 2Fc2)/3
3044 reflections(Δ/σ)max < 0.001
193 parametersΔρmax = 0.27 e Å3
0 restraintsΔρmin = −0.21 e Å3

Special details

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*/Ueq
C10.17131 (13)0.84678 (19)0.25979 (4)0.0187 (2)
C20.09703 (13)0.7573 (2)0.29780 (4)0.0211 (3)
H20.04870.61880.29340.025*
C30.09548 (13)0.8752 (2)0.34216 (4)0.0226 (3)
C40.16617 (13)1.0821 (2)0.34766 (4)0.0234 (3)
H40.16201.16280.37780.028*
C50.24143 (13)1.1703 (2)0.31029 (4)0.0214 (3)
H50.28941.30900.31480.026*
C60.24560 (12)1.05129 (18)0.26567 (4)0.0182 (2)
C70.31598 (12)1.08697 (18)0.22066 (4)0.0183 (2)
C80.41054 (13)1.25324 (19)0.20595 (4)0.0211 (3)
H80.43261.37960.22620.025*
C90.47011 (13)1.2281 (2)0.16144 (4)0.0224 (3)
H90.53741.33640.15160.027*
C100.43349 (13)1.04460 (19)0.12984 (4)0.0203 (2)
C110.33180 (13)0.88417 (18)0.14256 (4)0.0185 (2)
C120.27867 (12)0.90402 (18)0.18939 (4)0.0181 (2)
C130.01770 (15)0.7822 (2)0.38419 (5)0.0301 (3)
H13A−0.09330.82090.37840.045*
H13B0.06740.84130.41700.045*
H13C0.02840.62390.38460.045*
C140.50985 (13)1.0114 (2)0.08483 (4)0.0237 (3)
C150.47085 (14)0.7998 (2)0.05735 (4)0.0243 (3)
H15A0.54360.68610.07310.029*
H15B0.48570.81590.02140.029*
C160.30334 (14)0.72833 (19)0.05911 (4)0.0208 (2)
C170.27377 (17)0.5034 (2)0.03665 (5)0.0290 (3)
H17A0.34650.40030.05580.043*
H17B0.28950.50480.00100.043*
H17C0.16620.45980.03860.043*
C180.18336 (14)0.8888 (2)0.03275 (4)0.0229 (3)
H18A0.07790.83530.03450.034*
H18B0.19660.9043−0.00300.034*
H18C0.19831.03000.04970.034*
N10.19001 (11)0.76108 (16)0.21306 (4)0.0199 (2)
H10.15190.63660.20050.024*
O10.28283 (10)0.70934 (13)0.11287 (3)0.0218 (2)
O20.60210 (11)1.14169 (18)0.07137 (3)0.0341 (2)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
C10.0168 (5)0.0229 (6)0.0158 (5)0.0018 (4)0.0006 (4)−0.0007 (4)
C20.0178 (5)0.0256 (6)0.0194 (6)−0.0015 (4)0.0019 (4)0.0010 (5)
C30.0165 (5)0.0332 (7)0.0179 (6)0.0040 (5)0.0020 (4)0.0021 (5)
C40.0209 (6)0.0308 (7)0.0178 (6)0.0048 (5)0.0005 (4)−0.0051 (5)
C50.0198 (5)0.0224 (6)0.0208 (6)0.0029 (4)−0.0008 (4)−0.0027 (5)
C60.0156 (5)0.0204 (6)0.0176 (5)0.0021 (4)−0.0007 (4)0.0005 (4)
C70.0169 (5)0.0203 (6)0.0165 (5)0.0018 (4)−0.0008 (4)0.0001 (4)
C80.0214 (6)0.0205 (6)0.0197 (6)−0.0028 (4)−0.0018 (4)0.0002 (4)
C90.0203 (5)0.0247 (6)0.0210 (6)−0.0045 (5)−0.0009 (4)0.0041 (5)
C100.0180 (5)0.0246 (6)0.0175 (5)0.0004 (4)0.0006 (4)0.0031 (4)
C110.0200 (5)0.0183 (5)0.0166 (5)0.0019 (4)0.0011 (4)0.0008 (4)
C120.0171 (5)0.0189 (5)0.0177 (5)0.0003 (4)0.0008 (4)0.0018 (4)
C130.0265 (6)0.0436 (8)0.0214 (6)−0.0001 (6)0.0075 (5)0.0010 (5)
C140.0189 (5)0.0342 (7)0.0174 (6)0.0005 (5)0.0006 (4)0.0054 (5)
C150.0247 (6)0.0308 (7)0.0185 (6)0.0064 (5)0.0067 (5)0.0027 (5)
C160.0276 (6)0.0210 (6)0.0147 (5)0.0014 (5)0.0061 (4)−0.0001 (4)
C170.0454 (8)0.0219 (6)0.0214 (6)0.0018 (5)0.0107 (5)−0.0023 (5)
C180.0246 (6)0.0238 (6)0.0195 (6)0.0017 (5)0.0014 (4)−0.0012 (5)
N10.0239 (5)0.0189 (5)0.0170 (5)−0.0037 (4)0.0043 (4)−0.0015 (4)
O10.0317 (4)0.0192 (4)0.0156 (4)−0.0020 (3)0.0069 (3)−0.0008 (3)
O20.0287 (5)0.0506 (6)0.0240 (5)−0.0135 (4)0.0072 (4)0.0010 (4)

Geometric parameters (Å, °)

C1—N11.3845 (14)C11—C121.4010 (15)
C1—C21.3959 (16)C12—N11.3847 (14)
C1—C61.4132 (16)C13—H13A0.9800
C2—C31.3887 (17)C13—H13B0.9800
C2—H20.9500C13—H13C0.9800
C3—C41.4123 (18)C14—O21.2263 (15)
C3—C131.5079 (17)C14—C151.5078 (18)
C4—C51.3843 (17)C15—C161.5255 (17)
C4—H40.9500C15—H15A0.9900
C5—C61.4013 (16)C15—H15B0.9900
C5—H50.9500C16—O11.4744 (13)
C6—C71.4447 (15)C16—C171.5155 (17)
C7—C81.4064 (16)C16—C181.5239 (16)
C7—C121.4086 (16)C17—H17A0.9800
C8—C91.3739 (17)C17—H17B0.9800
C8—H80.9500C17—H17C0.9800
C9—C101.4156 (17)C18—H18A0.9800
C9—H90.9500C18—H18B0.9800
C10—C111.4016 (16)C18—H18C0.9800
C10—C141.4718 (16)N1—H10.8800
C11—O11.3638 (14)
N1—C1—C2129.29 (11)C3—C13—H13B109.5
N1—C1—C6108.89 (10)H13A—C13—H13B109.5
C2—C1—C6121.80 (10)C3—C13—H13C109.5
C3—C2—C1118.47 (11)H13A—C13—H13C109.5
C3—C2—H2120.8H13B—C13—H13C109.5
C1—C2—H2120.8O2—C14—C10123.03 (12)
C2—C3—C4119.90 (11)O2—C14—C15122.10 (11)
C2—C3—C13119.81 (12)C10—C14—C15114.83 (10)
C4—C3—C13120.28 (11)C14—C15—C16112.12 (10)
C5—C4—C3121.77 (11)C14—C15—H15A109.2
C5—C4—H4119.1C16—C15—H15A109.2
C3—C4—H4119.1C14—C15—H15B109.2
C4—C5—C6118.78 (11)C16—C15—H15B109.2
C4—C5—H5120.6H15A—C15—H15B107.9
C6—C5—H5120.6O1—C16—C17105.74 (9)
C5—C6—C1119.24 (11)O1—C16—C18108.67 (9)
C5—C6—C7133.95 (11)C17—C16—C18110.60 (10)
C1—C6—C7106.79 (10)O1—C16—C15108.32 (9)
C8—C7—C12120.57 (10)C17—C16—C15110.77 (10)
C8—C7—C6133.09 (11)C18—C16—C15112.48 (10)
C12—C7—C6106.29 (10)C16—C17—H17A109.5
C9—C8—C7118.24 (11)C16—C17—H17B109.5
C9—C8—H8120.9H17A—C17—H17B109.5
C7—C8—H8120.9C16—C17—H17C109.5
C8—C9—C10121.51 (11)H17A—C17—H17C109.5
C8—C9—H9119.2H17B—C17—H17C109.5
C10—C9—H9119.2C16—C18—H18A109.5
C11—C10—C9120.74 (11)C16—C18—H18B109.5
C11—C10—C14118.66 (11)H18A—C18—H18B109.5
C9—C10—C14120.47 (11)C16—C18—H18C109.5
O1—C11—C12117.93 (10)H18A—C18—H18C109.5
O1—C11—C10124.60 (10)H18B—C18—H18C109.5
C12—C11—C10117.46 (10)C1—N1—C12108.55 (9)
N1—C12—C11129.31 (10)C1—N1—H1125.7
N1—C12—C7109.45 (10)C12—N1—H1125.7
C11—C12—C7121.24 (10)C11—O1—C16115.16 (9)
C3—C13—H13A109.5
N1—C1—C2—C3179.15 (11)O1—C11—C12—N15.46 (17)
C6—C1—C2—C30.73 (17)C10—C11—C12—N1−173.73 (11)
C1—C2—C3—C40.88 (17)O1—C11—C12—C7−175.89 (10)
C1—C2—C3—C13−179.36 (10)C10—C11—C12—C74.92 (16)
C2—C3—C4—C5−1.64 (17)C8—C7—C12—N1177.69 (10)
C13—C3—C4—C5178.61 (11)C6—C7—C12—N10.03 (12)
C3—C4—C5—C60.72 (17)C8—C7—C12—C11−1.21 (16)
C4—C5—C6—C10.88 (16)C6—C7—C12—C11−178.86 (10)
C4—C5—C6—C7−177.44 (11)C11—C10—C14—O2−178.92 (11)
N1—C1—C6—C5179.66 (10)C9—C10—C14—O2−3.00 (18)
C2—C1—C6—C5−1.63 (16)C11—C10—C14—C15−1.16 (15)
N1—C1—C6—C7−1.60 (12)C9—C10—C14—C15174.76 (10)
C2—C1—C6—C7177.11 (10)O2—C14—C15—C16−148.09 (12)
C5—C6—C7—C82.2 (2)C10—C14—C15—C1634.13 (14)
C1—C6—C7—C8−176.28 (12)C14—C15—C16—O1−57.83 (12)
C5—C6—C7—C12179.42 (12)C14—C15—C16—C17−173.36 (10)
C1—C6—C7—C120.95 (12)C14—C15—C16—C1862.29 (13)
C12—C7—C8—C9−2.51 (16)C2—C1—N1—C12−176.93 (11)
C6—C7—C8—C9174.40 (11)C6—C1—N1—C121.64 (12)
C7—C8—C9—C102.39 (17)C11—C12—N1—C1177.74 (11)
C8—C9—C10—C111.44 (17)C7—C12—N1—C1−1.03 (12)
C8—C9—C10—C14−174.39 (11)C12—C11—O1—C16162.98 (10)
C9—C10—C11—O1175.84 (10)C10—C11—O1—C16−17.90 (15)
C14—C10—C11—O1−8.26 (17)C17—C16—O1—C11168.56 (10)
C9—C10—C11—C12−5.03 (16)C18—C16—O1—C11−72.69 (12)
C14—C10—C11—C12170.87 (10)C15—C16—O1—C1149.79 (12)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
C15—H15B···O2i0.992.483.4034 (13)155
N1—H1···Cg2ii0.882.973.5822 (11)128
C2—H2···Cg1ii0.952.743.5332 (13)141
C8—H8···Cg1iii0.952.913.4124 (12)114
C9—H9···Cg2iii0.952.743.4372 (13)130

Symmetry codes: (i) −x+1, −y+2, −z; (ii) −x, y−1/2, −z+1/2; (iii) −x+1, y+1/2, −z+1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HB2804).

References

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