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Acta Crystallogr Sect E Struct Rep Online. 2010 March 1; 66(Pt 3): o710.
Published online 2010 February 27. doi:  10.1107/S1600536810006744
PMCID: PMC2983581

8H-Chromeno[2′,3′:4,5]imidazo[2,1-a]isoquinoline

Abstract

The title compound, C18H12N2O, comprises two aromatic fragments, viz., imidazo[2,1-a]isoquinoline and benzene, linked by oxygen and methyl­ene bridges. Despite the absence of a common conjugative system within the mol­ecule, it adopts an essentially planar conformation with an r.m.s. deviation of 0. 036 Å. In the crystal, due to this structure, mol­ecules form stacks along the b axis by π(...)π stacking inter­actions, with shortest C(...)C distances in the range 3.340 (4)–3.510 (4) Å. The mol­ecules are bound by inter­molecular C—H(...)O inter­actions within the stacks and C—H(...)π inter­actions between the stacks.

Related literature

For background to cascade reactions, see: Bunce (1995 [triangle]); Tietze (1996 [triangle]); Parsons et al. (1996 [triangle]); Nicolaou et al. (2003 [triangle], 2006 [triangle]); Wasilke et al. (2005 [triangle]); Pellissier (2006a [triangle],b [triangle]); Parenty & Cronin (2008 [triangle]). For related compounds, see: Yadav et al. (2007 [triangle]); Kianmehr et al. (2009 [triangle]); Surpur et al. (2009 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-66-0o710-scheme1.jpg

Experimental

Crystal data

  • C18H12N2O
  • M r = 272.30
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-0o710-efi1.jpg
  • a = 11.9717 (15) Å
  • b = 6.0580 (8) Å
  • c = 17.948 (2) Å
  • β = 102.682 (3)°
  • V = 1269.9 (3) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.09 mm−1
  • T = 100 K
  • 0.40 × 0.12 × 0.02 mm

Data collection

  • Bruker APEXII CCD diffractometer
  • Absorption correction: multi-scan (SADABS; Sheldrick, 2003 [triangle]) T min = 0.965, T max = 0.998
  • 12413 measured reflections
  • 2734 independent reflections
  • 1821 reflections with I > 2σ(I)
  • R int = 0.056

Refinement

  • R[F 2 > 2σ(F 2)] = 0.066
  • wR(F 2) = 0.182
  • S = 1.00
  • 2734 reflections
  • 190 parameters
  • H-atom parameters constrained
  • Δρmax = 0.45 e Å−3
  • Δρmin = −0.23 e Å−3

Data collection: APEX2 (Bruker, 2005 [triangle]); cell refinement: SAINT-Plus (Bruker, 2001 [triangle]); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: SHELXTL (Sheldrick, 2008 [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/S1600536810006744/rk2193sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810006744/rk2193Isup2.hkl

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

supplementary crystallographic information

Comment

Cascade reactions have emerged as powerful tools to allow rapidly increasing molecular complexity (Tietze, 1996; Parsons et al., 1996; Wasilke et al., 2005). These processes avoid the excessive handling and isolation of synthetic intermediates generating less waste and thus contribute towards "Green Chemistry". Cascade reactions, in which multiple reactions are combined into one synthetic operation, have been reported extensively in the literature and have already become "state–of–the–art" in synthetic organic chemistry (Bunce, 1995; Nicolaou et al., 2003, 2006; Pellissier, 2006a, 2006b; Parenty & Cronin, 2008).

The title compound I, C18H12N2O, is the product of a novel cascade reaction (Fig. 1) (Yadav et al., 2007; Kianmehr et al., 2009; Surpur et al., 2009) starting with the Kroehnke condensation of salicylic aldehyde and isoquinolinium salt to afford the styryl derivative A, which forms zwitterion B upon thermally–induced cleavage of acetyl chloride. Then zwitterion B undergoes two consecutive nucleophilic cyclizations followed by [1,4]–proton shift to give the pentacycle I (Fig. 2). The single crystals of I suitable for X–ray diffraction analysis were obtained by slow crystallization from ethyl acetate solution.

Compound I comprises two aromatic fragments - imidazo[2,1–a]isoquinoline and benzene linked by the oxygen and methylene bridges (Fig. 3). Despite the absence of common conjugative system within the molecule, it adopts practically planar conformation, with the r.m.s. deviation of 0.036Å. In the crystal, due to this structure, molecules form stacks along the b axis by the stacking interactions [C1···C7Ai = 3.340 (4)Å, C2···C8i = 3.510Å, C2···C8Ai = 3.451 (4)Å, C3···C12Ai = 3.394 (4)Å, C13A···C14Bi = 3.496 (4)Å and C14A···C14Ai = 3.426 (4)Å] (Fig. 4). The molecules are also bound by the C8—H8A···O13ii [H···O = 2.71Å, C—H···O 157°] interactions within the stacks and the C8—H8B···π (C12Aiii—O13iii—C13Aiii) [H···C12A = 2.94Å, H···O13 = 2.80Å and H···C13A 2.81Å, C—H···O 175°] interactions between the stacks. Symmetry codes: (i) 1-x, 1-y, z; (ii) x, 1+y, z; (iii) 1.5-x, 0.5+y, 0.5-z.

Experimental

A water solution of K2CO3 (0.4 g in 1 ml of H2O) was added to a solution of freshly distilled salicylic aldehyde (0.18 g, 1.47 mmol) and 2–(cyanomethyl)isoquinolinium chloride (0.30 g, 1.47 mmol) in H2O (5 ml). The resulting mixture was stirred for 3 hours at 293 K. The precipitate formed was filtered–off and recrystallized from ethyl acetate / hexane mixture to give product I as colourless needles. Yield is 32%. M.p. = 444 K. Found (%): C 79.13, H4.58, N 10.53. Calcd. for C18H12N2O (%): C79.39, H 4.44, N 10.29. 1H NMR (400 MHz, CDCl3): δ = 4.25 (s, 2H, CH2), 6.98 (dd, 1H, H12, J11,12 = 8.1, J10,12 = 1.2), 7.01 (d, 1H, H5, J5,6 = 7.5), 7.07–7.12 (m, 2H, H9+H10), 7.16 (dd, 1H, H11, J11,12 = 8.1, J9,11 = 1.2), 7.40–7.45 (m, 1H, H3), 7.48–7.53 (m, 1H, H2), 7.55 (d, 1H, H4, J3,4 = 7.5), 7.58 (d, 1H, H6, J5,6 = 7.5), 8.47(d, 1H, H1, J1,2 = 8.1). 13C NMR (100 MHz, CDCl3): δ = 23.2 (CH2), 112.9 (CH), 117.8 (Cq), 118.1 (Cq), 118.3 (CH), 120.3 (CH), 123.1 (CH), 123.2 (Cq), 123.5 (CH), 127.1 (CH), 127.8 (CH), 128.2 (2xCH), 129.1 (Cq), 130.3 (CH), 138.0 (Cq), 152.0 (Cq), 161.1 (Cq). Mass spectrum (EI MS), m/z (Ir, %): 272 (70) [M+.], 136 (11), 128 (10).

Refinement

The hydrogen atoms were placed in calculated positions with C—H = 0.95–0.99Å and refined in the riding model with fixed isotropic displacement parameters [Uiso(H) = 1.2Ueq(C)].

Figures

Fig. 1.
Synthesis of compound I.
Fig. 2.
The plausible formation mechanism of I.
Fig. 3.
Molecular structure of Iwith the atom numbering scheme. Displacement ellipsoids are shown atthe 50% probability level. H atoms are presented as a small spheres of arbitrary radius.
Fig. 4.
Crystal packing of I viewed down the b axis. Dashed lines indicate the C—H···O and C—H···π interactions.

Crystal data

C18H12N2OF(000) = 568
Mr = 272.30Dx = 1.424 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ynCell parameters from 1700 reflections
a = 11.9717 (15) Åθ = 2.3–26.3°
b = 6.0580 (8) ŵ = 0.09 mm1
c = 17.948 (2) ÅT = 100 K
β = 102.682 (3)°Needle, colourless
V = 1269.9 (3) Å30.40 × 0.12 × 0.02 mm
Z = 4

Data collection

Bruker APEXII CCD diffractometer2734 independent reflections
Radiation source: fine–focus sealed tube1821 reflections with I > 2σ(I)
graphiteRint = 0.056
[var phi] and ω scansθmax = 27.0°, θmin = 1.9°
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)h = −15→15
Tmin = 0.965, Tmax = 0.998k = −7→7
12413 measured reflectionsl = −22→22

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)] = 0.066Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.182H-atom parameters constrained
S = 1.00w = 1/[σ2(Fo2) + (0.077P)2 + 1.7P] where P = (Fo2 + 2Fc2)/3
2734 reflections(Δ/σ)max < 0.001
190 parametersΔρmax = 0.45 e Å3
0 restraintsΔρmin = −0.23 e Å3

Special details

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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
C10.6165 (2)0.1766 (5)−0.07577 (16)0.0290 (6)
H10.57190.0665−0.05830.035*
C20.6436 (2)0.1563 (5)−0.14599 (17)0.0349 (7)
H20.61850.0302−0.17660.042*
C30.7068 (2)0.3167 (6)−0.17271 (17)0.0372 (7)
H30.72370.3008−0.22170.045*
C40.7447 (2)0.4957 (5)−0.12988 (17)0.0349 (7)
H40.78850.6033−0.14940.042*
C4A0.7213 (2)0.5276 (5)−0.05755 (16)0.0309 (6)
C50.7591 (2)0.7182 (5)−0.01180 (16)0.0332 (7)
H50.80520.8253−0.02950.040*
C60.7306 (2)0.7478 (5)0.05559 (16)0.0310 (6)
H60.75380.87770.08450.037*
N70.66701 (19)0.5884 (4)0.08314 (13)0.0269 (5)
C7A0.6332 (2)0.5823 (4)0.15238 (15)0.0251 (6)
C80.6498 (2)0.7432 (5)0.21381 (16)0.0326 (7)
H8A0.61410.88580.19500.039*
H8B0.73250.76760.23490.039*
C8A0.5921 (2)0.6458 (5)0.27520 (16)0.0301 (6)
C90.5902 (2)0.7644 (5)0.34032 (18)0.0347 (7)
H90.62610.90500.34660.042*
C100.5385 (3)0.6886 (5)0.39654 (18)0.0382 (7)
H100.53900.77520.44070.046*
C110.4851 (2)0.4809 (6)0.38774 (18)0.0387 (8)
H110.44830.42610.42580.046*
C120.4864 (2)0.3558 (5)0.32275 (16)0.0304 (6)
H120.45160.21410.31630.037*
C12A0.5393 (2)0.4417 (5)0.26757 (15)0.0264 (6)
O130.53167 (16)0.2981 (3)0.20489 (11)0.0319 (5)
C13A0.5786 (2)0.3795 (5)0.14856 (15)0.0297 (6)
N140.57698 (19)0.2676 (4)0.08385 (13)0.0297 (5)
C14A0.6311 (2)0.3960 (5)0.04379 (16)0.0291 (6)
C14B0.6554 (2)0.3618 (5)−0.02983 (14)0.0278 (6)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
C10.0230 (13)0.0287 (15)0.0340 (15)−0.0002 (11)0.0032 (11)0.0065 (12)
C20.0304 (15)0.0366 (16)0.0339 (16)0.0086 (13)−0.0012 (12)−0.0084 (13)
C30.0285 (15)0.056 (2)0.0270 (15)0.0063 (14)0.0051 (12)0.0020 (14)
C40.0300 (15)0.0386 (17)0.0360 (17)0.0009 (13)0.0072 (12)0.0117 (13)
C4A0.0256 (13)0.0281 (15)0.0354 (16)0.0053 (11)−0.0012 (12)−0.0019 (12)
C50.0312 (15)0.0325 (15)0.0360 (16)−0.0054 (12)0.0080 (12)0.0073 (13)
C60.0333 (15)0.0264 (14)0.0335 (15)0.0002 (12)0.0078 (12)0.0053 (12)
N70.0261 (11)0.0246 (12)0.0282 (12)0.0025 (9)0.0021 (9)0.0000 (10)
C7A0.0187 (12)0.0265 (14)0.0297 (14)−0.0019 (10)0.0045 (10)0.0056 (11)
C80.0258 (14)0.0372 (16)0.0350 (16)−0.0040 (12)0.0072 (12)−0.0058 (13)
C8A0.0209 (13)0.0325 (15)0.0350 (15)0.0021 (11)0.0020 (11)0.0023 (13)
C90.0278 (14)0.0313 (15)0.0440 (17)0.0019 (12)0.0055 (12)0.0008 (13)
C100.0365 (16)0.0407 (18)0.0362 (16)0.0091 (14)0.0054 (13)−0.0132 (14)
C110.0304 (15)0.051 (2)0.0388 (17)0.0089 (14)0.0175 (13)0.0082 (15)
C120.0239 (13)0.0275 (14)0.0397 (16)0.0001 (11)0.0067 (12)0.0026 (13)
C12A0.0214 (12)0.0294 (14)0.0283 (14)0.0068 (11)0.0055 (11)−0.0016 (11)
O130.0344 (11)0.0285 (10)0.0352 (11)−0.0058 (8)0.0130 (9)−0.0022 (9)
C13A0.0256 (14)0.0345 (15)0.0290 (14)0.0048 (12)0.0059 (11)0.0012 (12)
N140.0254 (11)0.0327 (13)0.0314 (13)0.0016 (10)0.0070 (9)0.0015 (10)
C14A0.0252 (13)0.0257 (14)0.0347 (15)0.0004 (11)0.0029 (11)−0.0018 (12)
C14B0.0227 (13)0.0376 (16)0.0214 (13)0.0105 (11)0.0014 (10)0.0021 (12)

Geometric parameters (Å, °)

C1—C21.374 (4)C8—C8A1.540 (4)
C1—C14B1.410 (4)C8—H8A0.9900
C1—H10.9500C8—H8B0.9900
C2—C31.380 (5)C8A—C91.377 (4)
C2—H20.9500C8A—C12A1.382 (4)
C3—C41.349 (5)C9—C101.373 (4)
C3—H30.9500C9—H90.9500
C4—C4A1.400 (4)C10—C111.405 (5)
C4—H40.9500C10—H100.9500
C4A—C51.432 (4)C11—C121.394 (4)
C4A—C14B1.432 (4)C11—H110.9500
C5—C61.339 (4)C12—C12A1.389 (4)
C5—H50.9500C12—H120.9500
C6—N71.386 (4)C12A—O131.409 (3)
C6—H60.9500O13—C13A1.353 (3)
N7—C14A1.382 (4)C13A—N141.341 (4)
N7—C7A1.390 (4)N14—C14A1.321 (4)
C7A—C13A1.386 (4)C14A—C14B1.429 (4)
C7A—C81.452 (4)
C2—C1—C14B119.6 (3)C8A—C8—H8B110.5
C2—C1—H1120.2H8A—C8—H8B108.7
C14B—C1—H1120.2C9—C8A—C12A117.3 (3)
C1—C2—C3120.9 (3)C9—C8A—C8120.1 (3)
C1—C2—H2119.6C12A—C8A—C8122.6 (3)
C3—C2—H2119.6C10—C9—C8A122.9 (3)
C4—C3—C2120.6 (3)C10—C9—H9118.5
C4—C3—H3119.7C8A—C9—H9118.5
C2—C3—H3119.7C9—C10—C11119.0 (3)
C3—C4—C4A121.9 (3)C9—C10—H10120.5
C3—C4—H4119.0C11—C10—H10120.5
C4A—C4—H4119.0C12—C11—C10119.5 (3)
C4—C4A—C5122.7 (3)C12—C11—H11120.2
C4—C4A—C14B117.6 (3)C10—C11—H11120.2
C5—C4A—C14B119.7 (3)C12A—C12—C11118.9 (3)
C6—C5—C4A121.0 (3)C12A—C12—H12120.5
C6—C5—H5119.5C11—C12—H12120.5
C4A—C5—H5119.5C8A—C12A—C12122.4 (3)
C5—C6—N7119.9 (3)C8A—C12A—O13125.4 (2)
C5—C6—H6120.1C12—C12A—O13112.2 (2)
N7—C6—H6120.1C13A—O13—C12A114.0 (2)
C14A—N7—C6122.6 (2)N14—C13A—O13122.2 (3)
C14A—N7—C7A108.4 (2)N14—C13A—C7A114.1 (2)
C6—N7—C7A129.0 (2)O13—C13A—C7A123.7 (2)
C13A—C7A—N7101.9 (2)C14A—N14—C13A104.9 (2)
C13A—C7A—C8128.1 (2)N14—C14A—N7110.7 (2)
N7—C7A—C8130.0 (2)N14—C14A—C14B129.9 (3)
C7A—C8—C8A106.1 (2)N7—C14A—C14B119.4 (3)
C7A—C8—H8A110.5C1—C14B—C14A123.3 (3)
C8A—C8—H8A110.5C1—C14B—C4A119.4 (2)
C7A—C8—H8B110.5C14A—C14B—C4A117.3 (3)
C14B—C1—C2—C3−1.1 (4)C11—C12—C12A—O13−178.9 (2)
C1—C2—C3—C40.9 (4)C8A—C12A—O13—C13A−2.1 (4)
C2—C3—C4—C4A−0.5 (4)C12—C12A—O13—C13A177.7 (2)
C3—C4—C4A—C5−178.9 (3)C12A—O13—C13A—N14−178.5 (2)
C3—C4—C4A—C14B0.2 (4)C12A—O13—C13A—C7A2.1 (4)
C4—C4A—C5—C6176.9 (3)N7—C7A—C13A—N14−0.3 (3)
C14B—C4A—C5—C6−2.3 (4)C8—C7A—C13A—N14180.0 (3)
C4A—C5—C6—N72.4 (4)N7—C7A—C13A—O13179.1 (2)
C5—C6—N7—C14A0.2 (4)C8—C7A—C13A—O13−0.6 (4)
C5—C6—N7—C7A176.8 (3)O13—C13A—N14—C14A−179.3 (2)
C14A—N7—C7A—C13A0.3 (3)C7A—C13A—N14—C14A0.1 (3)
C6—N7—C7A—C13A−176.7 (3)C13A—N14—C14A—N70.1 (3)
C14A—N7—C7A—C8−179.9 (3)C13A—N14—C14A—C14B179.9 (3)
C6—N7—C7A—C83.1 (5)C6—N7—C14A—N14177.0 (2)
C13A—C7A—C8—C8A−1.0 (4)C7A—N7—C14A—N14−0.3 (3)
N7—C7A—C8—C8A179.3 (2)C6—N7—C14A—C14B−2.8 (4)
C7A—C8—C8A—C9−177.9 (2)C7A—N7—C14A—C14B179.9 (2)
C7A—C8—C8A—C12A1.0 (4)C2—C1—C14B—C14A179.9 (3)
C12A—C8A—C9—C10−0.1 (4)C2—C1—C14B—C4A0.8 (4)
C8—C8A—C9—C10178.9 (3)N14—C14A—C14B—C13.9 (4)
C8A—C9—C10—C110.0 (4)N7—C14A—C14B—C1−176.3 (2)
C9—C10—C11—C120.6 (4)N14—C14A—C14B—C4A−176.9 (3)
C10—C11—C12—C12A−1.0 (4)N7—C14A—C14B—C4A2.8 (4)
C9—C8A—C12A—C12−0.4 (4)C4—C4A—C14B—C1−0.4 (4)
C8—C8A—C12A—C12−179.3 (2)C5—C4A—C14B—C1178.8 (2)
C9—C8A—C12A—O13179.4 (2)C4—C4A—C14B—C14A−179.5 (2)
C8—C8A—C12A—O130.5 (4)C5—C4A—C14B—C14A−0.4 (4)
C11—C12—C12A—C8A0.9 (4)

Hydrogen-bond geometry (Å, °)

Cg2 is the centroid of the O13,C12A,C8A,C8,C7A,C13A ring.
D—H···AD—HH···AD···AD—H···A
C8—H8A···O13i0.992.713.637 (4)157
C8—H8B···Cgii0.992.633.547 (3)154

Symmetry codes: (i) x, y+1, z; (ii) −x+3/2, y+1/2, −z+1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: RK2193).

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