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

Saifidin Safarov; Leonid G Voskressensky; Oksana V Bizhko; Larisa N Kulikova; Victor N Khrustalev

doi:10.1107/S1600536810006744

. 2010 Feb 27;66(Pt 3):o710. doi: 10.1107/S1600536810006744

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

Saifidin Safarov ^a,^*, Leonid G Voskressensky ^b, Oksana V Bizhko ^b, Larisa N Kulikova ^b, Victor N Khrustalev ^c

PMCID: PMC2983581 PMID: 21580448

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 ▶); Tietze (1996 ▶); Parsons et al. (1996 ▶); Nicolaou et al. (2003 ▶, 2006 ▶); Wasilke et al. (2005 ▶); Pellissier (2006a ▶,b ▶); Parenty & Cronin (2008 ▶). For related compounds, see: Yadav et al. (2007 ▶); Kianmehr et al. (2009 ▶); Surpur et al. (2009 ▶).

Experimental

Crystal data

C₁₈H₁₂N₂O
M _r = 272.30
Monoclinic,
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 ▶) 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
Δρ_max = 0.45 e Å⁻³
Δρ_min = −0.23 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: SAINT-Plus (Bruker, 2001 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810006744/rk2193sup1.cif

e-66-0o710-sup1.cif^{(19.1KB, cif)}

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

e-66-0o710-Isup2.hkl^{(134.3KB, hkl)}

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

Table 1. Hydrogen-bond geometry (Å, °).

Cg2 is the centroid of the O13,C12A,C8A,C8,C7A,C13A ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C8—H8A⋯O13ⁱ	0.99	2.71	3.637 (4)	157
C8—H8B⋯Cgⁱⁱ	0.99	2.63	3.547 (3)	154

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Symmetry codes: (i) Inline graphic ; (ii) .

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, J_11,12 = 8.1, J_10,12 = 1.2), 7.01 (d, 1H, H5, J_5,6 = 7.5), 7.07–7.12 (m, 2H, H9+H10), 7.16 (dd, 1H, H11, J_11,12 = 8.1, J_9,11 = 1.2), 7.40–7.45 (m, 1H, H3), 7.48–7.53 (m, 1H, H2), 7.55 (d, 1H, H4, J_3,4 = 7.5), 7.58 (d, 1H, H6, J_5,6 = 7.5), 8.47(d, 1H, H1, J_1,2 = 8.1). ¹³C NMR (100 MHz, CDCl₃): δ = 23.2 (CH₂), 112.9 (CH), 117.8 (C_q), 118.1 (C_q), 118.3 (CH), 120.3 (CH), 123.1 (CH), 123.2 (C_q), 123.5 (CH), 127.1 (CH), 127.8 (CH), 128.2 (2xCH), 129.1 (C_q), 130.3 (CH), 138.0 (C_q), 152.0 (C_q), 161.1 (C_q). Mass spectrum (EI MS), m/z (I_r, %): 272 (70) [M^+.], 136 (11), 128 (10).