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Acta Cryst. (2009). E65, o546    [ doi:10.1107/S1600536809005042 ]

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

N. Anuradha, A. Thiruvalluvar, K. Pandiarajan, S. Chitra and R. J. Butcher

Abstract top

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...[pi] interaction is present in the crystal structure.

Comment top

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).

Related literature top

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: Singh et al. (2004) and their cyclooxygenase inhibitory activity, see: Takechi et al. (2004).

Experimental top

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. .

Refinement top

H atoms were positioned geometrically and allowed to ride on their parent atom with C—H = 0.93 to 0.98 Å, and with Uiso(H) = 1.2 to 1.5 times Ueq(C).

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2008); cell refinement: CrysAlis RED (Oxford Diffraction, 2008); data reduction: CrysAlis RED (Oxford Diffraction, 2008); 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).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I), showing the atom-numbering scheme and displacement ellipsoids drawn at the 30% probability level. H atoms are shown as small spheres of arbitrary radius.
2-Methyl-3,5,6-triphenyl-2,3-dihydropyrazine top
Crystal data top
C23H20N2Z = 2
Mr = 324.41F(000) = 344
Triclinic, P1Dx = 1.156 Mg m−3
Hall symbol: -P 1Melting point: 460 K
a = 10.4406 (10) ÅCu Kα radiation, λ = 1.54184 Å
b = 10.5753 (7) ÅCell parameters from 5680 reflections
c = 11.0810 (13) Åθ = 5.2–77.4°
α = 93.439 (8)°µ = 0.52 mm−1
β = 114.161 (10)°T = 295 K
γ = 118.343 (9)°Prism, pale yellow
V = 931.9 (2) Å30.41 × 0.36 × 0.28 mm
Data collection top
Oxford Diffraction Gemini R
diffractometer		3852 independent reflections
Radiation source: fine-focus sealed tube3195 reflections with I > 2σ(I)
graphiteRint = 0.045
Detector resolution: 10.5081 pixels mm-1θmax = 77.5°, θmin = 5.2°
φ and ω scansh = −13→13
Absorption correction: analytical
(CrysAlis RED; Oxford Diffraction, 2008)		k = −13→10
Tmin = 0.831, Tmax = 0.885l = −13→13
8513 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.086Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.270H-atom parameters constrained
S = 1.09 w = 1/[σ2(Fo2) + (0.1784P)2 + 0.1376P]
where P = (Fo2 + 2Fc2)/3
3852 reflections(Δ/σ)max = 0.001
227 parametersΔρmax = 0.47 e Å−3
0 restraintsΔρmin = −0.27 e Å−3
Crystal data top
C23H20N2γ = 118.343 (9)°
Mr = 324.41V = 931.9 (2) Å3
Triclinic, P1Z = 2
a = 10.4406 (10) ÅCu Kα radiation
b = 10.5753 (7) ŵ = 0.52 mm−1
c = 11.0810 (13) ÅT = 295 K
α = 93.439 (8)°0.41 × 0.36 × 0.28 mm
β = 114.161 (10)°
Data collection top
Oxford Diffraction Gemini R
diffractometer		3852 independent reflections
Absorption correction: analytical
(CrysAlis RED; Oxford Diffraction, 2008)		3195 reflections with I > 2σ(I)
Tmin = 0.831, Tmax = 0.885Rint = 0.045
8513 measured reflectionsθmax = 77.5°
Refinement top
R[F2 > 2σ(F2)] = 0.086H-atom parameters constrained
wR(F2) = 0.270Δρmax = 0.47 e Å−3
S = 1.09Δρmin = −0.27 e Å−3
3852 reflectionsAbsolute structure: ?
227 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
Special details top

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles

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 > 2σ(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) top
xyzUiso*/Ueq
N10.0780 (2)0.1850 (2)−0.0471 (2)0.0633 (6)
N40.39318 (19)0.25469 (17)−0.01087 (17)0.0512 (5)
C20.0900 (3)0.0714 (2)−0.1158 (3)0.0613 (7)
C30.2375 (3)0.1513 (2)−0.1432 (2)0.0551 (6)
C50.3812 (2)0.3247 (2)0.0777 (2)0.0491 (5)
C60.2163 (2)0.3057 (2)0.0441 (2)0.0536 (6)
C21−0.0774 (3)−0.0383 (3)−0.2471 (3)0.0824 (9)
C310.2605 (3)0.0442 (2)−0.2156 (2)0.0587 (6)
C320.3089 (3)−0.0438 (3)−0.1466 (3)0.0712 (8)
C330.3318 (4)−0.1415 (3)−0.2108 (3)0.0873 (10)
C340.3090 (4)−0.1517 (3)−0.3418 (3)0.0930 (10)
C350.2604 (4)−0.0662 (4)−0.4115 (3)0.0901 (10)
C360.2364 (3)0.0324 (3)−0.3491 (3)0.0732 (8)
C510.5327 (2)0.4176 (2)0.2180 (2)0.0498 (6)
C520.5222 (3)0.4188 (3)0.3387 (3)0.0634 (7)
C530.6663 (3)0.4975 (3)0.4688 (3)0.0739 (9)
C540.8218 (3)0.5780 (3)0.4792 (3)0.0725 (8)
C550.8337 (3)0.5780 (3)0.3593 (3)0.0658 (7)
C560.6909 (2)0.4972 (2)0.2294 (2)0.0539 (6)
C610.2079 (3)0.4259 (2)0.1105 (2)0.0537 (6)
C620.0694 (3)0.3844 (3)0.1264 (3)0.0638 (7)
C630.0531 (3)0.4931 (3)0.1805 (3)0.0762 (10)
C640.1712 (4)0.6439 (3)0.2153 (3)0.0806 (10)
C650.3098 (3)0.6872 (3)0.1991 (3)0.0750 (9)
C660.3283 (3)0.5782 (3)0.1468 (3)0.0630 (7)
H20.112720.01451−0.052490.0736*
H30.216960.21204−0.202810.0661*
H21A−0.16525−0.07906−0.224110.1236*
H21B−0.07434−0.11930−0.287020.1236*
H21C−0.098240.01403−0.313080.1236*
H320.32603−0.03712−0.056630.0854*
H330.36313−0.20078−0.163770.1046*
H340.32629−0.21646−0.383720.1115*
H350.24329−0.07406−0.501590.1078*
H360.204070.09047−0.397210.0879*
H520.417480.366260.332460.0761*
H530.657830.495900.549110.0886*
H540.918240.632050.566370.0869*
H550.938640.632790.366180.0790*
H560.700220.495940.149490.0647*
H62−0.012990.282420.100220.0765*
H63−0.038350.464140.193380.0914*
H640.158480.716990.249760.0967*
H650.390290.789410.223420.0900*
H660.421240.607290.136140.0757*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0477 (9)0.0567 (10)0.0707 (12)0.0264 (8)0.0224 (8)0.0037 (8)
N40.0459 (8)0.0449 (8)0.0534 (9)0.0233 (7)0.0207 (7)0.0036 (6)
C20.0515 (11)0.0536 (11)0.0620 (12)0.0248 (9)0.0216 (9)0.0032 (9)
C30.0529 (10)0.0477 (10)0.0524 (11)0.0283 (8)0.0171 (9)0.0030 (8)
C50.0431 (9)0.0440 (9)0.0542 (10)0.0234 (7)0.0211 (8)0.0071 (7)
C60.0453 (9)0.0514 (10)0.0587 (11)0.0266 (8)0.0229 (8)0.0072 (8)
C210.0577 (13)0.0709 (15)0.0799 (17)0.0244 (11)0.0199 (12)−0.0044 (12)
C310.0504 (10)0.0485 (10)0.0551 (11)0.0260 (8)0.0127 (8)−0.0046 (8)
C320.0698 (14)0.0611 (12)0.0694 (14)0.0411 (11)0.0196 (11)0.0067 (10)
C330.0798 (17)0.0651 (14)0.092 (2)0.0482 (13)0.0160 (14)−0.0018 (13)
C340.0795 (17)0.0765 (17)0.093 (2)0.0488 (14)0.0179 (15)−0.0205 (15)
C350.0881 (19)0.094 (2)0.0633 (15)0.0484 (16)0.0244 (14)−0.0110 (14)
C360.0730 (14)0.0702 (14)0.0593 (13)0.0419 (12)0.0185 (11)0.0014 (10)
C510.0462 (9)0.0463 (9)0.0546 (11)0.0275 (8)0.0221 (8)0.0048 (7)
C520.0570 (11)0.0717 (13)0.0623 (12)0.0368 (10)0.0303 (10)0.0081 (10)
C530.0755 (15)0.0947 (17)0.0516 (12)0.0510 (14)0.0290 (11)0.0056 (11)
C540.0594 (12)0.0782 (15)0.0551 (12)0.0384 (11)0.0115 (10)−0.0064 (10)
C550.0464 (10)0.0626 (12)0.0670 (13)0.0249 (9)0.0197 (10)−0.0003 (10)
C560.0481 (10)0.0512 (10)0.0552 (11)0.0256 (8)0.0233 (8)0.0057 (8)
C610.0484 (10)0.0577 (10)0.0552 (11)0.0330 (9)0.0224 (8)0.0101 (8)
C620.0544 (11)0.0722 (13)0.0677 (13)0.0380 (10)0.0296 (10)0.0164 (10)
C630.0703 (14)0.1005 (19)0.0767 (16)0.0583 (15)0.0393 (12)0.0184 (14)
C640.0844 (17)0.0880 (17)0.0815 (17)0.0620 (15)0.0363 (14)0.0059 (13)
C650.0728 (14)0.0619 (13)0.0844 (17)0.0404 (12)0.0326 (13)0.0053 (11)
C660.0554 (11)0.0586 (12)0.0741 (14)0.0331 (10)0.0309 (10)0.0084 (10)
Geometric parameters (Å, °) top
N1—C21.466 (4)C62—C631.377 (5)
N1—C61.279 (3)C63—C641.372 (4)
N4—C31.469 (3)C64—C651.389 (6)
N4—C51.276 (3)C65—C661.387 (5)
C2—C31.535 (4)C2—H20.9800
C2—C211.519 (4)C3—H30.9800
C3—C311.514 (4)C21—H21A0.9600
C5—C61.510 (3)C21—H21B0.9600
C5—C511.487 (3)C21—H21C0.9600
C6—C611.487 (3)C32—H320.9300
C31—C321.386 (4)C33—H330.9300
C31—C361.382 (4)C34—H340.9300
C32—C331.384 (5)C35—H350.9300
C33—C341.360 (4)C36—H360.9300
C34—C351.368 (5)C52—H520.9300
C35—C361.390 (5)C53—H530.9300
C51—C521.386 (4)C54—H540.9300
C51—C561.396 (3)C55—H550.9300
C52—C531.388 (4)C56—H560.9300
C53—C541.377 (5)C62—H620.9300
C54—C551.384 (4)C63—H630.9300
C55—C561.382 (4)C64—H640.9300
C61—C621.389 (5)C65—H650.9300
C61—C661.386 (4)C66—H660.9300
N1···N42.848 (3)H2···C52.8400
N4···N12.848 (3)H2···C322.9200
N1···H622.5700H2···H322.5500
N1···H2i2.7800H2···N1i2.7800
N4···H322.7800H3···C62.8600
N4···H562.6400H3···H21C2.5600
N4···H33ii2.8300H3···H362.3600
N4···H66iii2.7500H3···C55iii3.0100
C32···C32ii3.585 (5)H3···C56iii2.8300
C51···C663.207 (4)H21B···C312.7700
C52···C663.407 (5)H21C···H32.5600
C52···C613.261 (4)H21C···C35v3.0600
C61···C523.261 (4)H21C···H35v2.3300
C62···C64iv3.479 (4)H32···N42.7800
C64···C62iv3.479 (4)H32···C23.0500
C66···C513.207 (4)H32···H22.5500
C66···C523.407 (5)H32···C33ii3.0600
C2···H323.0500H33···N4ii2.8300
C5···H22.8400H33···C51ii3.0900
C5···H662.8100H33···C56ii2.9000
C6···H522.8300H35···H21Cv2.3300
C6···H32.8600H36···H32.3600
C31···H21B2.7700H52···C62.8300
C32···H22.9200H52···C612.8900
C33···H32ii3.0600H52···H53vi2.4800
C35···H65iii3.0200H53···C52vi3.0500
C35···H21Cv3.0600H53···H52vi2.4800
C36···H65iii2.9900H56···N42.6400
C51···H662.7900H62···N12.5700
C51···H33ii3.0900H65···C35iii3.0200
C52···H53vi3.0500H65···C36iii2.9900
C55···H3iii3.0100H66···C52.8100
C56···H33ii2.9000H66···C512.7900
C56···H3iii2.8300H66···N4iii2.7500
C61···H522.8900
C2—N1—C6116.8 (2)C21—C2—H2108.00
C3—N4—C5116.3 (2)N4—C3—H3108.00
N1—C2—C3109.45 (18)C2—C3—H3108.00
N1—C2—C21109.0 (3)C31—C3—H3108.00
C3—C2—C21113.5 (2)C2—C21—H21A109.00
N4—C3—C2109.53 (19)C2—C21—H21B109.00
N4—C3—C31109.3 (2)C2—C21—H21C109.00
C2—C3—C31113.97 (18)H21A—C21—H21B109.00
N4—C5—C6121.10 (19)H21A—C21—H21C110.00
N4—C5—C51117.5 (2)H21B—C21—H21C109.00
C6—C5—C51121.34 (19)C31—C32—H32120.00
N1—C6—C5120.0 (2)C33—C32—H32120.00
N1—C6—C61117.9 (2)C32—C33—H33120.00
C5—C6—C61122.14 (19)C34—C33—H33120.00
C3—C31—C32119.6 (2)C33—C34—H34120.00
C3—C31—C36121.8 (2)C35—C34—H34120.00
C32—C31—C36118.5 (3)C34—C35—H35120.00
C31—C32—C33120.4 (3)C36—C35—H35120.00
C32—C33—C34120.7 (3)C31—C36—H36120.00
C33—C34—C35119.6 (4)C35—C36—H36120.00
C34—C35—C36120.7 (3)C51—C52—H52120.00
C31—C36—C35120.1 (3)C53—C52—H52120.00
C5—C51—C52121.7 (2)C52—C53—H53120.00
C5—C51—C56119.25 (19)C54—C53—H53120.00
C52—C51—C56118.9 (2)C53—C54—H54120.00
C51—C52—C53120.7 (3)C55—C54—H54120.00
C52—C53—C54120.1 (3)C54—C55—H55120.00
C53—C54—C55119.7 (3)C56—C55—H55120.00
C54—C55—C56120.5 (3)C51—C56—H56120.00
C51—C56—C55120.1 (2)C55—C56—H56120.00
C6—C61—C62119.0 (2)C61—C62—H62120.00
C6—C61—C66121.5 (3)C63—C62—H62120.00
C62—C61—C66119.4 (3)C62—C63—H63120.00
C61—C62—C63120.5 (3)C64—C63—H63120.00
C62—C63—C64120.2 (4)C63—C64—H64120.00
C63—C64—C65119.9 (3)C65—C64—H64120.00
C64—C65—C66120.1 (3)C64—C65—H65120.00
C61—C66—C65119.8 (3)C66—C65—H65120.00
N1—C2—H2108.00C61—C66—H66120.00
C3—C2—H2108.00C65—C66—H66120.00
C6—N1—C2—C3−38.6 (3)C5—C6—C61—C62−151.9 (2)
C6—N1—C2—C21−163.2 (2)C5—C6—C61—C6633.1 (3)
C2—N1—C6—C5−0.8 (3)C3—C31—C32—C33−179.5 (3)
C2—N1—C6—C61177.16 (19)C36—C31—C32—C33−0.2 (5)
C5—N4—C3—C2−37.2 (3)C3—C31—C36—C35179.4 (3)
C5—N4—C3—C31−162.71 (18)C32—C31—C36—C350.1 (5)
C3—N4—C5—C6−2.4 (3)C31—C32—C33—C340.7 (5)
C3—N4—C5—C51173.76 (17)C32—C33—C34—C35−1.0 (6)
N1—C2—C3—N457.9 (3)C33—C34—C35—C360.9 (6)
N1—C2—C3—C31−179.37 (19)C34—C35—C36—C31−0.4 (6)
C21—C2—C3—N4179.9 (2)C5—C51—C52—C53175.2 (3)
C21—C2—C3—C31−57.3 (3)C56—C51—C52—C53−0.1 (4)
N4—C3—C31—C3256.1 (3)C5—C51—C56—C55−176.7 (2)
N4—C3—C31—C36−123.2 (3)C52—C51—C56—C55−1.3 (4)
C2—C3—C31—C32−66.8 (3)C51—C52—C53—C541.3 (5)
C2—C3—C31—C36113.9 (3)C52—C53—C54—C55−1.0 (5)
N4—C5—C6—N125.0 (3)C53—C54—C55—C56−0.4 (5)
N4—C5—C6—C61−152.88 (19)C54—C55—C56—C511.6 (4)
C51—C5—C6—N1−151.0 (2)C6—C61—C62—C63−176.5 (2)
C51—C5—C6—C6131.1 (3)C66—C61—C62—C63−1.4 (4)
N4—C5—C51—C52−138.4 (2)C6—C61—C66—C65175.3 (2)
N4—C5—C51—C5636.9 (3)C62—C61—C66—C650.3 (4)
C6—C5—C51—C5237.7 (3)C61—C62—C63—C642.0 (4)
C6—C5—C51—C56−147.0 (2)C62—C63—C64—C65−1.6 (4)
N1—C6—C61—C6230.2 (3)C63—C64—C65—C660.5 (4)
N1—C6—C61—C66−144.8 (2)C64—C65—C66—C610.1 (4)
Symmetry codes: (i) −x, −y, −z; (ii) −x+1, −y, −z; (iii) −x+1, −y+1, −z; (iv) −x, −y+1, −z; (v) −x, −y, −z−1; (vi) −x+1, −y+1, −z+1.
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
C65—H65···Cg(C31–C36)iii0.932.973.834 (3)156
Symmetry codes: (iii) −x+1, −y+1, −z.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
C65—H65···Cg(C31–C36)i0.932.973.834 (3)156
Symmetry codes: (i) −x+1, −y+1, −z.
Acknowledgements top

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 program (grant No. CHE-0619278) for funds to purchase an X-ray diffractometer.

references
References top

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