2-Amino-7,7-dimethyl-5-oxo-4-(p-tol­yl)-5,6,7,8-tetra­hydro-4H-chromene-3-carbonitrile

Sumati Anthal; Goutam Brahmachari; Sujay Laskar; Bubun Banerjee; Rajni Kant; Vivek K Gupta

doi:10.1107/S1600536812033570

. 2012 Jul 28;68(Pt 8):o2592–o2593. doi: 10.1107/S1600536812033570

2-Amino-7,7-dimethyl-5-oxo-4-(p-tolyl)-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile

Sumati Anthal ^a, Goutam Brahmachari ^b, Sujay Laskar ^b, Bubun Banerjee ^b, Rajni Kant ^a, Vivek K Gupta ^a,^*

PMCID: PMC3415029 PMID: 22905016

Abstract

In the title molecule, C₁₉H₂₀N₂O₂, the cyclohexene ring adopts a sofa conformation, while the pyran ring adopts a flattened boat conformation. In the crystal, molecules are linked by N—H⋯N and N—H⋯O hydrogen bonds, forming a two-dimensional network parallel to (010).

Related literature

For background to compounds containing the 4H-pyran unit, see: Brahmachari (2010 ▶); Hatakeyama et al. (1988 ▶). For the biological activity of compounds containing a tetrahydrobenzo[b]pyran ring system, see: Andreani & Lapi (1960 ▶); Bonsignore et al. (1993 ▶); Brahmachari (2011 ▶); Konkoy et al. (2001 ▶). For 2-amino-4H-pyrans as photoactive materials, see: Armetso et al. (1989 ▶). For the synthesis of related compounds, see: Jin et al. (2004 ▶); Balalaie et al. (2007 ▶). For related structures, see: Tu et al. (2001 ▶); Wang (2011 ▶). For ring conformations, see: Duax et al. (1975 ▶).

Experimental

Crystal data

C₁₉H₂₀N₂O₂
M _r = 308.37
Monoclinic,
a = 9.4622 (3) Å
b = 16.8820 (5) Å
c = 10.8301 (4) Å
β = 111.842 (4)°
V = 1605.82 (9) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 293 K
0.30 × 0.20 × 0.20 mm

Data collection

Oxford Diffraction Xcalibur Sapphire3 diffractometer
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2010 ▶) T _min = 0.862, T _max = 1.000
18449 measured reflections
3149 independent reflections
2428 reflections with I > 2σ(I)
R _int = 0.037

Refinement

R[F ² > 2σ(F ²)] = 0.046
wR(F ²) = 0.115
S = 1.05
3149 reflections
219 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.20 e Å⁻³
Δρ_min = −0.22 e Å⁻³

Data collection: CrysAlis PRO (Oxford Diffraction, 2010 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶); software used to prepare material for publication: PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812033570/lh5503sup1.cif

e-68-o2592-sup1.cif^{(25.6KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812033570/lh5503Isup2.hkl

e-68-o2592-Isup2.hkl^{(151.4KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536812033570/lh5503Isup3.cml

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

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N13—H131⋯O5ⁱ	0.89 (2)	2.06 (2)	2.913 (2)	161 (2)
N13—H132⋯N15ⁱⁱ	0.87 (2)	2.35 (2)	3.168 (2)	156 (2)

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

Acknowledgments

SL is grateful to the CSIR, New Delhi, for the award of a Senior Research Fellowship. BB is grateful to the UGC, New Delhi, for the awarding of a Junior Research Fellowship. RK acknowledges the Department of Science & Technology for the single-crystal X-ray diffractometer sanctioned as a National Facility under project No. SR/S2/CMP-47/2003.

supplementary crystallographic information

Comment

4H-Pyran units constitute structural features of a broad range of bioactive natural products (Brahmachari, 2010; Hatakeyama et al., 1988). The tetrahydrobenzo[b]pyran ring is of particular interest because compounds bearing this structural motif exhibit diverse biological activities such as spasmolytic, anticancer and anti-anaphylactin agents (Andreani et al., 1960; Bonsignore et al., 1993), anti-Alzheimer's disease (Brahmachari, 2011), anti-Huntington's disease, anti-Parkinson's disease and anti-HIV (Konkoy et al., 2001). 2-Amino-4H-pyrans have also been found to be useful as photoactive materials (Armetso et al., 1989). Hence, investigation of the structural features of biologically relevant tetrahydrobenzo[b]pyran derivatives is of both scientific and practical interest. In continuation of our efforts to develop useful synthetic protocols for biologically significant molecules, we herein report an efficient and environmentally benign synthesis and the crystal structure of the title compound. The bond lengths and angles of the title compound are normal and correspond to those observed in related structures (Tu et al., 2001; Wang, 2011). The cyclohexene ring adopts a sofa conformation while the pyran ring adopts a flattened boat conformation with asymmetry parameters [ΔCs(C7) = 5.71] and [ΔCs (O1—C4) = 0.08; ΔCs (C2—C3) = 9.8)] respectively (Duax et al., 1975). In the crystal structure, intermolecular N—H···N and N—H···O hydrogen bonds link the molecules into a two-dimensional network parallel to (010) (Fig.2).

Experimental

The synthesis of the title compounds was carried out via one-pot multi-component reaction in aqueous ethanol using low-cost and environmentally benign sodium formate as catalyst at room temperature. An oven-dried screw cap test tube was charged with a magnetic stir bar, p-methylbenzaldehyde (0.12 g, 1 mmol), malononitrile (0.066 g, 1 mmol) and sodium formate (0.136 g, 20 mol %) in 5 ml aqueous ethanol. The reaction mixture was then started to stir vigorously and after 20 min 1 mmol of dimedone (0.14 g) was added, and continued to stir. After completion of the overall reaction (2 h) as monitored by TLC, a white solid was precipitated out, filtered off, and washed with aqueous ethanol. Recrystallization from ethanol afforded the title compound as white block-shaped crystals (252 mg, yield 82%) with the m.p. 492–494 K (lit. 492–495 K) (Balalaie et al., 2007). Rf 0.82 (EtOAc). White solid; FT—IR (KBr) νmax 3375, 3256, 3180, 2961, 2920, 2885, 2187, 1677, 1637, 1607, 1512, 1460, 1414, 1366, 1215, 1137, 1030, 825, 764, 565 cm-1; 1H-NMR (DMSO-d6, 400 MHz) & 13 C-NMR (DMSO-d6; 100 MHz) data are in excellent agreement with literature values (Jin et al., 2004; Balalaie et al., 2007); TOF-MS: calculated for C₁₉H₂₀N₂O₂Na 331.1422 [M + Na]+; found 331.1426. For crystallization 60 mg of the compound was dissolved in 20 ml mixture of ethanol and water (5:1) and left for several days at ambient temperature which yielded white block-shaped crystals.