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organic compounds
(4aR*,8aS*)-2,3-Diphenyl-4a,5,6,7,8,8a-hexahydroquinoxaline
aDepartment of Chemistry, Tongji University, Shanghai 200092, People's Republic of China
*Correspondence e-mail: fanly@tongji.edu.cn
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
|
Data collection: APEX2 (Bruker, 2004); cell 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
https://doi.org/10.1107/S1600536812028061/hb6855sup1.cif
contains datablocks I, global. DOI: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
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
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.Hydrogen atoms were positioned geometrically and allowed to ride on their parent atoms, with C–H = 0.93–0.98 Å, and with Uiso(H) values set to 1.2Ueq(C).
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
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).
For background to dihydropyrazine derivatives, see: Raw et al. (2003). For related structures, see: Reich et al. (2004); Wang et al. (2008).
Data collection: APEX2 (Bruker, 2004); cell
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). ![]() | Fig. 1. The molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level. |
C20H20N2 | F(000) = 616 |
Mr = 288.38 | Dx = 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 |
Bruker SMART APEX CCD diffractometer | 2739 independent reflections |
Radiation source: fine-focus sealed tube | 2703 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.010 |
phi and ω scans | θmax = 72.6°, θmin = 5.7° |
Absorption correction: multi-scan (SADABS; Bruker, 2004) | h = −7→5 |
Tmin = 0.902, Tmax = 0.949 | k = −15→16 |
4074 measured reflections | l = −17→23 |
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(Fo2) + (0.0617P)2 + 0.1364P] where P = (Fo2 + 2Fc2)/3 |
S = 1.05 | (Δ/σ)max < 0.001 |
2739 reflections | Δρmax = 0.14 e Å−3 |
199 parameters | Δρmin = −0.14 e Å−3 |
0 restraints | Absolute structure: unk |
Primary atom site location: structure-invariant direct methods |
C20H20N2 | V = 1645.14 (4) Å3 |
Mr = 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 |
Bruker SMART APEX CCD diffractometer | 2739 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2004) | 2703 reflections with I > 2σ(I) |
Tmin = 0.902, Tmax = 0.949 | Rint = 0.010 |
4074 measured reflections |
R[F2 > 2σ(F2)] = 0.036 | 0 restraints |
wR(F2) = 0.099 | H-atom parameters constrained |
S = 1.05 | Δρmax = 0.14 e Å−3 |
2739 reflections | Δρmin = −0.14 e Å−3 |
199 parameters | Absolute structure: unk |
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. |
x | y | z | Uiso*/Ueq | ||
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* |
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) |
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 |
Mr | 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) |
Tmin, Tmax | 0.902, 0.949 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 4074, 2739, 2703 |
Rint | 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 |
Δρmax, Δρmin (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
Bruker (20004). APEX2, SAINT-Plus and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Raw, S. A., Wilfred, C. D. & Taylor, R. J. K. (2003). Chem. Commun. pp. 2286–2287. Web of Science CrossRef Google Scholar
Reich, B. J. E., Justice, A. K., Beckstead, B. T., Reibenspies, J. H. & Miller, S. A. (2004). J. Org. Chem. 69, 1357–1359. Web of Science CSD CrossRef PubMed CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
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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).