(4aR*,8aS*)-2,3-Diphenyl-4a,5,6,7,8,8a-hexa­hydro­quinoxaline

Chen, W.; Tang, K.-S.; Fan, L.-Y.

doi:10.1107/S1600536812028061

organic compounds

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ISSN: 2056-9890

Volume 68| Part 7| July 2012| Page o2212

https://doi.org/10.1107/S1600536812028061

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(4aR,8aS)-2,3-Diphenyl-4a,5,6,7,8,8a-hexahydroquinoxaline

W. Chen,^a K.-S. Tang ^a and L.-Y. Fan ^a ^*

^aDepartment of Chemistry, Tongji University, Shanghai 200092, People's Republic of China
^*Correspondence e-mail: fanly@tongji.edu.cn

(Received 15 June 2012; accepted 20 June 2012; online 27 June 2012)

In the title compound, C₂₀H₂₀N₂, the quinoxaline ring adopts a very distorted half-chair conformation [N=C—C=N = 22.7 (2)° for the nominally coplanar atoms] and the cyclohexane ring adopts a chair conformation. The quinoxaline and cyclohexane rings are cis-fused. The two phenyl rings form a dihedral angle of 63.88 (7)°.

Related literature

For background to dihydropyrazine derivatives, see: Raw et al. (2003 ). For related structures, see: Reich et al. (2004 ); Wang et al. (2008).

Experimental

Crystal data

C₂₀H₂₀N₂
M_r = 288.38
Orthorhombic, P 2₁ 2₁ 2₁
a = 6.3546 (1) Å
b = 13.4894 (2) Å
c = 19.1921 (3) Å
V = 1645.14 (4) Å³
Z = 4
Cu Kα radiation
μ = 0.52 mm⁻¹
T = 293 K
0.20 × 0.20 × 0.10 mm

Data collection

Bruker SMART APEX CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2004) T_min = 0.902, T_max = 0.949
4074 measured reflections
2739 independent reflections
2703 reflections with I > 2σ(I)
R_int = 0.010

Refinement

R[F² > 2σ(F²)] = 0.036
wR(F²) = 0.099
S = 1.05
2739 reflections
199 parameters
H-atom parameters constrained
Δρ_max = 0.14 e Å⁻³
Δρ_min = −0.14 e Å⁻³

Data collection: APEX2 (Bruker, 2004); 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: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S1600536812028061/hb6855sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536812028061/hb6855Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S1600536812028061/hb6855Isup3.cml

checkCIF report

Comment top

Dihydropyrazine ring systems are found as a key unit in natural products and biochemical materials (Raw et al., 2003). Therefore, the synthesis of dihydropyrazine derivatives attract much interest in organic chemistry. In this respect, we report herein the crystal structure of the title compound.

In the title compound, Fig. 1, the quinoxaline ring has a very distorted half-chair conformation and the cyclohexane ring has a chair conformation. The dihedral angle between the two benzene rings is 63.88 (7)°. The lengths of the C═N bonds [1.2678 (18)Å] are comparable to those in similar compounds (Wang et al., 2008; Reich et al., 2004).

Related literature top

For background to dihydropyrazine derivatives, see: Raw et al. (2003). For related structures, see: Reich et al. (2004); Wang et al. (2008).

Experimental top

2-hydroxy-1,2-diphenylethanone (0.212 g, 1 mmol) and YbCl₃ (0.028 g, 0.1 mmol) were dissolved in 5 ml EtOH and stirred until the solid dissolved completely in refluxing, then (1R,2S)-cyclohexane-1,2-diamine (0.171 g, 1.5 mmol) and H₂O₂ (0.022 g, 0.2 mmol) were added into the mixture. After 30 min, TLC showed the reaction to be complete. The reaction mixture was cooled to room temperature. The solvent was evaporated in vacuum and the product purified by column chromatography on neutral alumina deactivated with H₂O (6 wt%) (PE-EtOAc = 5:1) to give the title compound. The compound was recrystallized from methanol to give yellow blocks.

Structure description top

For background to dihydropyrazine derivatives, see: Raw et al. (2003). For related structures, see: Reich et al. (2004); Wang et al. (2008).

Computing details top

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); 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: SHELXL97 (Sheldrick, 2008).

Figures top

Fig. 1. The molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level.

(4aR*,8aS*)-2,3-Diphenyl-4a,5,6,7,8,8a-hexahydroquinoxaline top

Crystal data top

C₂₀H₂₀N₂	F(000) = 616
M_r = 288.38	D_x = 1.164 Mg m⁻³
Orthorhombic, P2₁2₁2₁	Cu Kα radiation, λ = 1.54178 Å
Hall symbol: P 2ac 2ab	Cell parameters from 2779 reflections
a = 6.3546 (1) Å	θ = 3.3–72.4°
b = 13.4894 (2) Å	µ = 0.52 mm⁻¹
c = 19.1921 (3) Å	T = 293 K
V = 1645.14 (4) Å³	Block, yellow
Z = 4	0.20 × 0.20 × 0.10 mm

Data collection top

Bruker SMART APEX CCD diffractometer	2739 independent reflections
Radiation source: fine-focus sealed tube	2703 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.010
phi and ω scans	θ_max = 72.6°, θ_min = 5.7°
Absorption correction: multi-scan (SADABS; Bruker, 2004)	h = −7→5
T_min = 0.902, T_max = 0.949	k = −15→16
4074 measured reflections	l = −17→23

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F² > 2σ(F²)] = 0.036	H-atom parameters constrained
wR(F²) = 0.099	w = 1/[σ²(F_o²) + (0.0617P)² + 0.1364P] where P = (F_o² + 2F_c²)/3
S = 1.05	(Δ/σ)_max < 0.001
2739 reflections	Δρ_max = 0.14 e Å⁻³
199 parameters	Δρ_min = −0.14 e Å⁻³
0 restraints	Absolute structure: unk
Primary atom site location: structure-invariant direct methods

Crystal data top

C₂₀H₂₀N₂	V = 1645.14 (4) Å³
M_r = 288.38	Z = 4
Orthorhombic, P2₁2₁2₁	Cu Kα radiation
a = 6.3546 (1) Å	µ = 0.52 mm⁻¹
b = 13.4894 (2) Å	T = 293 K
c = 19.1921 (3) Å	0.20 × 0.20 × 0.10 mm

Data collection top

Bruker SMART APEX CCD diffractometer	2739 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2004)	2703 reflections with I > 2σ(I)
T_min = 0.902, T_max = 0.949	R_int = 0.010
4074 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.036	0 restraints
wR(F²) = 0.099	H-atom parameters constrained
S = 1.05	Δρ_max = 0.14 e Å⁻³
2739 reflections	Δρ_min = −0.14 e Å⁻³
199 parameters	Absolute structure: unk

Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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) top

	x	y	z	U_iso*/U_eq
N1	0.18801 (18)	0.39372 (8)	0.62663 (6)	0.0410 (3)
N2	−0.0579 (2)	0.33893 (9)	0.50829 (6)	0.0492 (3)
C1	0.1165 (2)	0.29069 (10)	0.61739 (7)	0.0419 (3)
H1B	0.2255	0.2542	0.5920	0.050*
C2	0.0862 (3)	0.24167 (12)	0.68822 (8)	0.0544 (4)
H2B	0.0632	0.1712	0.6818	0.065*
H2C	0.2128	0.2501	0.7158	0.065*
C3	−0.0991 (3)	0.28592 (15)	0.72680 (8)	0.0654 (5)
H3A	−0.0700	0.3549	0.7372	0.079*
H3B	−0.1183	0.2512	0.7706	0.079*
C4	−0.2993 (3)	0.27893 (16)	0.68428 (11)	0.0674 (5)
H4A	−0.4138	0.3100	0.7096	0.081*
H4B	−0.3353	0.2098	0.6772	0.081*
C5	−0.2729 (2)	0.32958 (14)	0.61387 (10)	0.0605 (4)
H5A	−0.3992	0.3200	0.5863	0.073*
H5B	−0.2536	0.4002	0.6208	0.073*
C6	−0.0850 (2)	0.28777 (10)	0.57496 (7)	0.0453 (3)
H6A	−0.1155	0.2181	0.5647	0.054*
C7	0.1606 (2)	0.45124 (10)	0.57517 (7)	0.0388 (3)
C8	0.0606 (2)	0.41514 (9)	0.50853 (7)	0.0414 (3)
C9	0.2231 (3)	0.55791 (10)	0.58259 (7)	0.0442 (3)
C10	0.4058 (3)	0.58177 (13)	0.61799 (9)	0.0591 (4)
H10A	0.4885	0.5318	0.6371	0.071*
C11	0.4658 (4)	0.68056 (16)	0.62502 (11)	0.0769 (6)
H11A	0.5903	0.6965	0.6479	0.092*
C12	0.3419 (5)	0.75417 (13)	0.59834 (10)	0.0843 (8)
H12A	0.3823	0.8201	0.6031	0.101*
C13	0.1589 (5)	0.73123 (13)	0.56464 (10)	0.0803 (7)
H13A	0.0740	0.7816	0.5472	0.096*
C14	0.0993 (4)	0.63297 (11)	0.55626 (9)	0.0614 (4)
H14A	−0.0247	0.6177	0.5328	0.074*
C15	0.1024 (3)	0.46329 (10)	0.43996 (7)	0.0444 (3)
C16	0.2983 (3)	0.50275 (13)	0.42434 (8)	0.0535 (4)
H16A	0.4023	0.5054	0.4584	0.064*
C17	0.3394 (3)	0.53842 (14)	0.35770 (9)	0.0631 (4)
H17A	0.4713	0.5644	0.3473	0.076*
C18	0.1862 (4)	0.53548 (13)	0.30698 (9)	0.0634 (5)
H18A	0.2147	0.5590	0.2624	0.076*
C19	−0.0101 (3)	0.49741 (13)	0.32258 (8)	0.0605 (4)
H19A	−0.1142	0.4958	0.2886	0.073*
C20	−0.0522 (3)	0.46158 (11)	0.38877 (8)	0.0514 (4)
H20A	−0.1848	0.4362	0.3990	0.062*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0362 (5)	0.0423 (6)	0.0445 (6)	−0.0035 (5)	0.0028 (5)	−0.0021 (5)
N2	0.0577 (7)	0.0453 (6)	0.0446 (6)	−0.0099 (6)	−0.0039 (6)	−0.0055 (5)
C1	0.0413 (7)	0.0367 (6)	0.0476 (7)	0.0000 (6)	0.0081 (6)	−0.0014 (6)
C2	0.0568 (9)	0.0541 (8)	0.0523 (8)	−0.0089 (7)	0.0006 (7)	0.0092 (7)
C3	0.0728 (11)	0.0777 (11)	0.0458 (8)	−0.0250 (10)	0.0162 (8)	−0.0067 (8)
C4	0.0529 (9)	0.0777 (11)	0.0716 (10)	−0.0188 (9)	0.0248 (8)	−0.0114 (10)
C5	0.0380 (7)	0.0664 (10)	0.0771 (11)	−0.0071 (7)	0.0026 (7)	−0.0018 (9)
C6	0.0510 (7)	0.0387 (6)	0.0462 (7)	−0.0117 (6)	0.0013 (6)	−0.0057 (6)
C7	0.0368 (6)	0.0378 (6)	0.0419 (6)	−0.0007 (5)	0.0043 (5)	−0.0047 (5)
C8	0.0455 (7)	0.0360 (6)	0.0427 (6)	0.0001 (6)	0.0007 (6)	−0.0060 (5)
C9	0.0560 (8)	0.0390 (7)	0.0376 (6)	−0.0067 (6)	0.0075 (6)	−0.0065 (5)
C10	0.0606 (9)	0.0534 (8)	0.0632 (9)	−0.0126 (8)	0.0026 (8)	−0.0113 (7)
C11	0.0866 (13)	0.0702 (12)	0.0738 (12)	−0.0356 (11)	0.0105 (11)	−0.0232 (10)
C12	0.148 (2)	0.0435 (9)	0.0617 (10)	−0.0306 (12)	0.0243 (14)	−0.0141 (8)
C13	0.142 (2)	0.0406 (8)	0.0581 (9)	0.0044 (11)	0.0039 (13)	−0.0052 (7)
C14	0.0894 (12)	0.0426 (7)	0.0522 (8)	0.0040 (8)	−0.0030 (9)	−0.0040 (6)
C15	0.0567 (8)	0.0340 (6)	0.0425 (7)	0.0010 (6)	0.0005 (6)	−0.0050 (5)
C16	0.0607 (9)	0.0529 (8)	0.0469 (7)	−0.0056 (8)	0.0019 (7)	−0.0016 (7)
C17	0.0737 (11)	0.0616 (9)	0.0539 (8)	−0.0074 (9)	0.0126 (8)	0.0062 (7)
C18	0.0919 (13)	0.0539 (8)	0.0443 (8)	0.0018 (9)	0.0072 (8)	0.0071 (7)
C19	0.0833 (12)	0.0513 (8)	0.0469 (8)	0.0057 (9)	−0.0121 (8)	0.0012 (7)
C20	0.0616 (9)	0.0428 (7)	0.0496 (8)	−0.0009 (7)	−0.0029 (7)	−0.0028 (6)

Geometric parameters (Å, º) top

N1—C7	1.2680 (18)	C9—C14	1.378 (2)
N1—C1	1.4728 (17)	C9—C10	1.383 (2)
N2—C8	1.2745 (19)	C10—C11	1.393 (3)
N2—C6	1.4638 (19)	C10—H10A	0.9300
C1—C6	1.518 (2)	C11—C12	1.367 (4)
C1—C2	1.524 (2)	C11—H11A	0.9300
C1—H1B	0.9800	C12—C13	1.366 (4)
C2—C3	1.513 (2)	C12—H12A	0.9300
C2—H2B	0.9700	C13—C14	1.388 (3)
C2—H2C	0.9700	C13—H13A	0.9300
C3—C4	1.515 (3)	C14—H14A	0.9300
C3—H3A	0.9700	C15—C16	1.387 (2)
C3—H3B	0.9700	C15—C20	1.390 (2)
C4—C5	1.523 (3)	C16—C17	1.391 (2)
C4—H4A	0.9700	C16—H16A	0.9300
C4—H4B	0.9700	C17—C18	1.377 (3)
C5—C6	1.517 (2)	C17—H17A	0.9300
C5—H5A	0.9700	C18—C19	1.381 (3)
C5—H5B	0.9700	C18—H18A	0.9300
C6—H6A	0.9800	C19—C20	1.385 (2)
C7—C9	1.4996 (18)	C19—H19A	0.9300
C7—C8	1.5087 (18)	C20—H20A	0.9300
C8—C15	1.4914 (19)

C7—N1—C1	116.18 (11)	C9—C7—C8	120.12 (12)
C8—N2—C6	116.52 (12)	N2—C8—C15	116.95 (12)
N1—C1—C6	110.45 (11)	N2—C8—C7	120.82 (12)
N1—C1—C2	109.94 (12)	C15—C8—C7	122.18 (11)
C6—C1—C2	111.15 (12)	C14—C9—C10	119.24 (15)
N1—C1—H1B	108.4	C14—C9—C7	121.25 (14)
C6—C1—H1B	108.4	C10—C9—C7	119.49 (14)
C2—C1—H1B	108.4	C9—C10—C11	120.01 (19)
C3—C2—C1	111.32 (14)	C9—C10—H10A	120.0
C3—C2—H2B	109.4	C11—C10—H10A	120.0
C1—C2—H2B	109.4	C12—C11—C10	120.1 (2)
C3—C2—H2C	109.4	C12—C11—H11A	120.0
C1—C2—H2C	109.4	C10—C11—H11A	120.0
H2B—C2—H2C	108.0	C13—C12—C11	120.20 (17)
C2—C3—C4	111.43 (13)	C13—C12—H12A	119.9
C2—C3—H3A	109.3	C11—C12—H12A	119.9
C4—C3—H3A	109.3	C12—C13—C14	120.2 (2)
C2—C3—H3B	109.3	C12—C13—H13A	119.9
C4—C3—H3B	109.3	C14—C13—H13A	119.9
H3A—C3—H3B	108.0	C9—C14—C13	120.2 (2)
C3—C4—C5	110.93 (13)	C9—C14—H14A	119.9
C3—C4—H4A	109.5	C13—C14—H14A	119.9
C5—C4—H4A	109.5	C16—C15—C20	119.22 (14)
C3—C4—H4B	109.5	C16—C15—C8	121.16 (14)
C5—C4—H4B	109.5	C20—C15—C8	119.41 (14)
H4A—C4—H4B	108.0	C15—C16—C17	119.99 (16)
C6—C5—C4	110.90 (15)	C15—C16—H16A	120.0
C6—C5—H5A	109.5	C17—C16—H16A	120.0
C4—C5—H5A	109.5	C18—C17—C16	120.46 (18)
C6—C5—H5B	109.5	C18—C17—H17A	119.8
C4—C5—H5B	109.5	C16—C17—H17A	119.8
H5A—C5—H5B	108.0	C17—C18—C19	119.72 (15)
N2—C6—C5	110.33 (13)	C17—C18—H18A	120.1
N2—C6—C1	110.95 (11)	C19—C18—H18A	120.1
C5—C6—C1	112.96 (12)	C18—C19—C20	120.20 (17)
N2—C6—H6A	107.4	C18—C19—H19A	119.9
C5—C6—H6A	107.4	C20—C19—H19A	119.9
C1—C6—H6A	107.4	C19—C20—C15	120.39 (17)
N1—C7—C9	118.48 (12)	C19—C20—H20A	119.8
N1—C7—C8	121.37 (12)	C15—C20—H20A	119.8

Experimental details

Crystal data
Chemical formula	C₂₀H₂₀N₂
M_r	288.38
Crystal system, space group	Orthorhombic, P2₁2₁2₁
Temperature (K)	293
a, b, c (Å)	6.3546 (1), 13.4894 (2), 19.1921 (3)
V (Å³)	1645.14 (4)
Z	4
Radiation type	Cu Kα
µ (mm⁻¹)	0.52
Crystal size (mm)	0.20 × 0.20 × 0.10

Data collection
Diffractometer	Bruker SMART APEX CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2004)
T_min, T_max	0.902, 0.949
No. of measured, independent and observed [I > 2σ(I)] reflections	4074, 2739, 2703
R_int	0.010
(sin θ/λ)_max (Å⁻¹)	0.619

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.036, 0.099, 1.05
No. of reflections	2739
No. of parameters	199
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.14, −0.14
Absolute structure	Unk

Computer programs: APEX2 (Bruker, 2004), SAINT-Plus (Bruker, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Acknowledgements

This work was supported by the National Natural Scientific Foundation of China (No. 1380234048).

References

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