2-Methyl-3,5,6-triphenyl-2,3-dihydro­pyrazine

N Anuradha; A Thiruvalluvar; K Pandiarajan; S Chitra; R J Butcher

doi:10.1107/S1600536809005042

. 2009 Feb 18;65(Pt 3):o546. doi: 10.1107/S1600536809005042

2-Methyl-3,5,6-triphenyl-2,3-dihydropyrazine

N Anuradha ^a, A Thiruvalluvar ^a,^*, K Pandiarajan ^b, S Chitra ^b, R J Butcher ^c

PMCID: PMC2968533 PMID: 21582205

Abstract

In the title molecule, C₂₃H₂₀N₂, the heterocyclic ring adopts a screw-boat conformation, with all substituents equatorial. The phenyl ring at position 3 makes dihedral angles of 78.12 (15) and 72.67 (15)°, respectively, with the phenyl rings at positions 5 and 6; the dihedral angle between the phenyl rings at positions 5 and 6 is 67.32 (14)°. A C—H⋯π interaction is present in the crystal structure.

Related literature

Some 2-alkyl-3,5,6-triphenyl-2,3-dihydropyrazines have been reported to exhibit fluorescence in the solid-state, see: Baliah & Pandiarajan (1978 ▶). For the use of dihydropyrazines in medicine, in particular with reference to DNA breakage activity, see: Yamaguchi et al. (2003 ▶). For their biological activity, see: Takechi et al. (2004 ▶) and their cyclooxygenase inhibitory activity, see: Singh et al. (2004 ▶).

Experimental

Crystal data

C₂₃H₂₀N₂
M _r = 324.41
Triclinic,
a = 10.4406 (10) Å
b = 10.5753 (7) Å
c = 11.0810 (13) Å
α = 93.439 (8)°
β = 114.161 (10)°
γ = 118.343 (9)°
V = 931.9 (2) Å³
Z = 2
Cu Kα radiation
μ = 0.52 mm⁻¹
T = 295 K
0.41 × 0.36 × 0.28 mm

Data collection

Oxford Diffraction Gemini R diffractometer
Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2008 ▶) T _min = 0.831, T _max = 0.885
8513 measured reflections
3852 independent reflections
3195 reflections with I > 2σ(I)
R _int = 0.045

Refinement

R[F ² > 2σ(F ²)] = 0.086
wR(F ²) = 0.270
S = 1.09
3852 reflections
227 parameters
H-atom parameters constrained
Δρ_max = 0.47 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Data collection: CrysAlis CCD (Oxford Diffraction, 2008 ▶); cell refinement: CrysAlis RED (Oxford Diffraction, 2008 ▶); data reduction: CrysAlis RED; program(s) used to solve structure: SIR2004 (Burla et al., 2005 ▶); 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 datablocks global, I. DOI: 10.1107/S1600536809005042/tk2373sup1.cif

e-65-0o546-sup1.cif^{(22.9KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809005042/tk2373Isup2.hkl

e-65-0o546-Isup2.hkl^{(185KB, hkl)}

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

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

Cg is the centroid of the C31–C36 ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C65—H65⋯Cgⁱ	0.93	2.97	3.834 (3)	156

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Symmetry code: (i) Inline graphic .

Acknowledgments

AT thanks the UGC, India, for the award of a Minor Research Project [File No. MRP-2355/06 (UGC-SERO), Link No. 2355, 10/01/2007]. RJB acknowledges the NSF MRI programme (grant No. CHE-0619278) for funds to purchase the X-ray diffractometer.

supplementary crystallographic information

Comment

Some 2-alkyl-3,5,6-triphenyl-2,3-dihydropyrazines have been reported to exhibit fluorescence in the solid-state (Baliah & Pandiarajan, 1978). Dihydropyrazines are used in medicine, in particular with reference to DNA breakage activity (Yamaguchi et al., 2003). They also exhibit biological effects (Takechi et al., 2004) such as growth inhibition of Escherichia coli and cyclooxygenase inhibitory activity (Singh et al., 2004).

In the title molecule (I), Fig. 1, the heterocyclic ring adopts a screw-boat conformation, with all substituents equatorial. The phenyl ring at position 3 forms dihedral angles of 78.12 (15)° and 72.67 (15)° with the phenyl rings at positions 5 and 6, respectively. The dihedral angle between the phenyl rings at positions 5 and 6 is 67.32 (14)°. The most prominent intermolecular interaction in the crystal structure is a C65—H65···π contact involving the C31–C36 phenyl ring (Table 1).

Experimental

To a homogeneous solution of benzil (1.05 g, 0.005 mol) and 1-methyl-2-phenyl-1,2-ethanediamine dihydrochloride (1.11 g, 0.005 mol) in ethanol (20 ml), sodium acetate trihydrate (2.04 g, 0.015 mol) was added. The precipitated sodium chloride was filtered off and the filtrate was refluxed for 2 h. On completion of the reaction, as indicated by TLC, the reaction mixture was poured into crushed ice and the resulting solid was filtered and purified by column chromatography on silica gel. Elution with benzene–petroleum ether 333–353 K (4:1 v/v) gave the pure product in 1.72 g (80%) yield. .