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Acta Cryst. (2008). E64, o1977    [ doi:10.1107/S1600536808029905 ]

1,2,3-Triphenyl-1,2-dihydroquinoxaline

F. T. Edelmann, S. Blaurock, V. Lorenz and A. Fischer

Abstract top

The title compound, C26H20N2, first reported in 1891, was obtained as a by-product in the preparation of benzildianil from benzil and excess aniline. The dihedral angles between the fused benzene ring and the pendant phenyl rings are 17.93 (11), 53.18 (10) and 89.08 (12)°.

Comment top

The title compound, 1,2,4-triphenyl-1,2-dihydroquinoxaline (1), was first reported as early as 1891 by Kehrmann & Messinger. In the original paper the compound was named `quinoxaline base from benzoin and phenylphenylenediamine' and was already assigned the correct structure. It was described as `magnificent uranium-yellow crystals' showing a bright blue–green fluorescence in solution (alcohols, ether, benzene) (Kehrmann & Messinger, 1891). In 1960, Bodforss used 1 and substituted derivatives thereof to prepare cationic quinoxalinium salts which in many respects resembled the well known triphenylmethane dyes (Bodforss, 1960). For example, the dimethylamino derivatives were found to give blue solutions, while the dihydroxyphenyl derivative was orange–red. The only other report on 1 found in the literature is a paper by Sannicolò entitled `New Heterocyclic Syntheses from Benzil Dianils' (Sannicolò , 1983). In this paper it was reported that 1 is formed as a by-product in the preparation of benzildianil from benzil and excess aniline in the presence of 4-toluenesulfonic acid as catalyst. Under suitable reaction conditions the isolated yield of 1 can be as high as 31% (Sannicolò, 1983). We obtained the beautiful yellow crystals of the title compound by chance in minor amounts as a by-product in the preparation of benzildianil according to the literature procedure (Siegfied et al., 1892; Lorenz et al., 1994). A crystal structure determination of revealed the presence of 1,2,4-triphenyl-1,2-dihydroquinoxaline (1) containing three adjacent phenyl substituents attached to the 1,2-dihydroquinoxaline core. With a short distance of 1.282 (3) Å the C2—N2 bond is clearly a double bond. Thus this study confirmed that Kehrmann & Messinger had assigned the correct structure of the title compound almost 120 years ago (Kehrmann & Messinger, 1891).

Related literature top

For related literature, see: Bodforss (1960); Kehrmann & Messinger (1891); Sannicolò (1983); Lorenz et al. (1994); Siegfied et al. (1892).

Experimental top

Well formed, bright yellow single crystals of the title compound were obtained as a minor by-product (less than 5% isolated yield) during a preparation of benzildianil from benzil and excess aniline according to the literature (Lorenz et al., 1994).

Refinement top

H atoms were refined using a riding model, with aromatic C—H = 0.95 Å, tertiary C—H = 0.99 Å and Uiso(H) = 1.2Ueq(C).

Computing details top

Data collection: DIF4 (Stoe & Cie, 1992); cell refinement: DIF4 (Stoe & Cie, 1992); data reduction: REDU4 (Stoe & Cie, 1992); program(s) used to solve structure: SHELXS86 (Sheldrick, 2008); program(s) used to refine structure: SHELXL96 (Sheldrick, 2008); molecular graphics: XP5 in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL96 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecule of the title compound in the crystal. Displacement ellipsoids represent 50% probability levels. H-Atom radii are arbitrary.
1,2,3-Triphenyl-1,2-dihydroquinoxaline top
Crystal data top
C26H20N2F(000) = 760
Mr = 360.44Dx = 1.236 Mg m−3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P2ynCell parameters from 58 reflections
a = 10.121 (2) Åθ = 10–11.5°
b = 10.374 (2) ŵ = 0.07 mm−1
c = 18.572 (4) ÅT = 143 K
β = 96.49 (3)°Prism, yellow
V = 1937.4 (7) Å30.40 × 0.25 × 0.20 mm
Z = 4
Data collection top
Stoe STADI4
diffractometer		Rint = 0.038
Radiation source: fine-focus sealed tubeθmax = 25.0°, θmin = 3.1°
graphiteh = −11→12
ω/θ scansk = −12→6
5587 measured reflectionsl = −22→0
3413 independent reflections3 standard reflections every 90 min
2249 reflections with I > 2σ(I) intensity decay: none
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)] = 0.053Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.120H-atom parameters constrained
S = 1.06 w = 1/[σ2(Fo2) + (0.0357P)2 + 0.6314P]
where P = (Fo2 + 2Fc2)/3
3413 reflections(Δ/σ)max < 0.001
253 parametersΔρmax = 0.17 e Å−3
0 restraintsΔρmin = −0.20 e Å−3
Crystal data top
C26H20N2V = 1937.4 (7) Å3
Mr = 360.44Z = 4
Monoclinic, P21/nMo Kα radiation
a = 10.121 (2) ŵ = 0.07 mm−1
b = 10.374 (2) ÅT = 143 K
c = 18.572 (4) Å0.40 × 0.25 × 0.20 mm
β = 96.49 (3)°
Data collection top
Stoe STADI4
diffractometer		Rint = 0.038
5587 measured reflectionsθmax = 25.0°
3413 independent reflections3 standard reflections every 90 min
2249 reflections with I > 2σ(I) intensity decay: none
Refinement top
R[F2 > 2σ(F2)] = 0.053H-atom parameters constrained
wR(F2) = 0.120Δρmax = 0.17 e Å−3
S = 1.06Δρmin = −0.20 e Å−3
3413 reflectionsAbsolute structure: ?
253 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
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. Weighted R-factors wR and all goodnesses of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The observed criterion of F2 > σ(F2) is used only for calculating _R_factor_obs 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
N10.03731 (18)0.21070 (18)0.24908 (10)0.0289 (5)
C1−0.0288 (2)0.3104 (2)0.28694 (12)0.0288 (5)
H1−0.06010.37830.25080.035*
C20.0724 (2)0.3722 (2)0.34379 (12)0.0284 (5)
N20.16822 (18)0.30815 (19)0.37782 (10)0.0330 (5)
C30.1878 (2)0.1800 (2)0.35655 (13)0.0314 (6)
C40.2750 (2)0.1022 (2)0.40081 (14)0.0403 (6)
H40.31310.13380.44650.048*
C50.3068 (2)−0.0197 (3)0.37920 (14)0.0429 (7)
H50.3662−0.07220.40970.052*
C60.2513 (2)−0.0648 (3)0.31256 (13)0.0389 (6)
H60.2745−0.14830.29710.047*
C70.1631 (2)0.0087 (2)0.26827 (13)0.0339 (6)
H70.1251−0.02460.22290.041*
C80.1293 (2)0.1322 (2)0.28974 (12)0.0290 (5)
C11−0.0053 (2)0.1892 (2)0.17475 (12)0.0275 (5)
C120.0861 (2)0.1544 (2)0.12738 (12)0.0311 (5)
H120.17690.14230.14520.037*
C130.0448 (2)0.1374 (2)0.05486 (12)0.0325 (6)
H130.10780.11400.02290.039*
C14−0.0871 (2)0.1540 (2)0.02785 (13)0.0378 (6)
H14−0.11510.1413−0.02220.045*
C15−0.1772 (2)0.1891 (2)0.07428 (13)0.0375 (6)
H15−0.26770.20170.05600.045*
C16−0.1375 (2)0.2062 (2)0.14755 (13)0.0333 (6)
H16−0.20100.22970.17920.040*
C21−0.1490 (2)0.2648 (2)0.32301 (12)0.0325 (6)
C22−0.1641 (3)0.1378 (3)0.34323 (14)0.0440 (7)
H22−0.09930.07560.33380.053*
C23−0.2732 (3)0.1008 (3)0.37709 (16)0.0583 (8)
H23−0.28230.01360.39140.070*
C24−0.3685 (3)0.1902 (4)0.39001 (15)0.0589 (9)
H24−0.44380.16440.41280.071*
C25−0.3549 (3)0.3163 (3)0.37011 (14)0.0514 (8)
H25−0.42020.37810.37930.062*
C26−0.2458 (2)0.3532 (3)0.33650 (13)0.0405 (6)
H26−0.23700.44060.32250.049*
C310.0561 (2)0.5091 (2)0.36335 (12)0.0288 (5)
C320.0050 (2)0.6012 (2)0.31318 (14)0.0368 (6)
H32−0.02290.57590.26470.044*
C340.0335 (2)0.7668 (3)0.40346 (15)0.0429 (7)
H340.02590.85440.41710.052*
C350.0839 (2)0.6766 (3)0.45398 (14)0.0403 (6)
H350.11060.70230.50250.048*
C360.0956 (2)0.5495 (2)0.43407 (13)0.0339 (6)
H360.13120.48840.46910.041*
C33−0.0058 (3)0.7291 (2)0.33302 (15)0.0426 (7)
H33−0.04020.79100.29810.051*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0282 (10)0.0312 (12)0.0270 (10)0.0036 (9)0.0016 (8)−0.0023 (9)
C10.0295 (12)0.0277 (13)0.0289 (12)0.0019 (10)0.0021 (10)−0.0023 (11)
C20.0275 (12)0.0320 (14)0.0261 (12)−0.0033 (11)0.0044 (9)0.0001 (11)
N20.0305 (11)0.0336 (12)0.0338 (11)0.0007 (9)−0.0008 (9)−0.0005 (9)
C30.0278 (12)0.0299 (14)0.0354 (13)−0.0002 (10)−0.0006 (10)0.0024 (11)
C40.0389 (14)0.0384 (16)0.0410 (15)0.0018 (12)−0.0073 (12)−0.0018 (12)
C50.0398 (15)0.0372 (16)0.0492 (16)0.0059 (12)−0.0068 (12)0.0047 (13)
C60.0391 (14)0.0346 (15)0.0436 (15)0.0050 (12)0.0079 (12)0.0024 (12)
C70.0338 (13)0.0328 (15)0.0356 (13)0.0022 (11)0.0066 (11)−0.0026 (11)
C80.0247 (12)0.0319 (14)0.0308 (12)0.0004 (10)0.0051 (10)0.0036 (11)
C110.0306 (12)0.0236 (13)0.0281 (12)−0.0026 (10)0.0028 (10)−0.0018 (10)
C120.0299 (12)0.0309 (14)0.0321 (13)−0.0014 (11)0.0017 (10)−0.0013 (11)
C130.0397 (14)0.0280 (14)0.0306 (13)0.0011 (11)0.0069 (11)−0.0031 (11)
C140.0478 (15)0.0353 (15)0.0289 (13)0.0001 (12)−0.0009 (11)−0.0026 (11)
C150.0337 (14)0.0410 (16)0.0355 (14)0.0014 (12)−0.0058 (11)−0.0034 (12)
C160.0288 (13)0.0361 (15)0.0353 (13)0.0014 (11)0.0054 (10)−0.0035 (11)
C210.0271 (12)0.0416 (16)0.0282 (13)−0.0030 (11)0.0011 (10)−0.0096 (11)
C220.0421 (15)0.0428 (17)0.0489 (16)−0.0065 (13)0.0137 (13)−0.0051 (14)
C230.0592 (19)0.058 (2)0.0613 (19)−0.0188 (16)0.0202 (16)−0.0030 (16)
C240.0383 (16)0.089 (3)0.0526 (18)−0.0173 (17)0.0193 (14)−0.0163 (18)
C250.0333 (15)0.076 (2)0.0463 (17)0.0024 (15)0.0094 (12)−0.0148 (16)
C260.0342 (14)0.0492 (18)0.0378 (14)0.0043 (12)0.0031 (11)−0.0073 (13)
C310.0245 (12)0.0293 (14)0.0326 (13)−0.0010 (10)0.0033 (10)−0.0023 (11)
C320.0372 (14)0.0348 (15)0.0374 (14)−0.0026 (11)−0.0008 (11)−0.0002 (12)
C340.0413 (16)0.0297 (15)0.0584 (18)−0.0026 (12)0.0084 (13)−0.0072 (13)
C350.0400 (14)0.0418 (17)0.0399 (15)−0.0037 (12)0.0080 (11)−0.0116 (13)
C360.0315 (13)0.0366 (15)0.0338 (13)0.0006 (11)0.0043 (11)−0.0009 (12)
C330.0441 (16)0.0301 (15)0.0523 (17)0.0003 (12)−0.0003 (13)0.0049 (13)
Geometric parameters (Å, °) top
N1—C81.394 (3)C14—H140.9500
N1—C111.417 (3)C15—C161.386 (3)
N1—C11.455 (3)C15—H150.9500
C1—C21.527 (3)C16—H160.9500
C1—C211.529 (3)C21—C221.383 (3)
C1—H11.0000C21—C261.385 (3)
C2—N21.282 (3)C22—C231.385 (4)
C2—C311.480 (3)C22—H220.9500
N2—C31.408 (3)C23—C241.379 (4)
C3—C41.394 (3)C23—H230.9500
C3—C81.404 (3)C24—C251.370 (4)
C4—C51.376 (3)C24—H240.9500
C4—H40.9500C25—C261.383 (4)
C5—C61.382 (3)C25—H250.9500
C5—H50.9500C26—H260.9500
C6—C71.375 (3)C31—C321.392 (3)
C6—H60.9500C31—C361.393 (3)
C7—C81.395 (3)C32—C331.385 (3)
C7—H70.9500C32—H320.9500
C11—C161.387 (3)C34—C331.380 (4)
C11—C121.394 (3)C34—C351.381 (4)
C12—C131.376 (3)C34—H340.9500
C12—H120.9500C35—C361.379 (3)
C13—C141.383 (3)C35—H350.9500
C13—H130.9500C36—H360.9500
C14—C151.372 (3)C33—H330.9500
C8—N1—C11123.18 (19)C14—C15—C16120.8 (2)
C8—N1—C1117.98 (18)C14—C15—H15119.6
C11—N1—C1118.46 (18)C16—C15—H15119.6
N1—C1—C2108.88 (18)C15—C16—C11120.1 (2)
N1—C1—C21115.09 (19)C15—C16—H16119.9
C2—C1—C21109.38 (18)C11—C16—H16119.9
N1—C1—H1107.7C22—C21—C26118.7 (2)
C2—C1—H1107.7C22—C21—C1122.1 (2)
C21—C1—H1107.7C26—C21—C1119.2 (2)
N2—C2—C31118.4 (2)C21—C22—C23120.4 (3)
N2—C2—C1122.3 (2)C21—C22—H22119.8
C31—C2—C1119.24 (19)C23—C22—H22119.8
C2—N2—C3118.30 (19)C24—C23—C22120.1 (3)
C4—C3—C8119.5 (2)C24—C23—H23119.9
C4—C3—N2118.8 (2)C22—C23—H23119.9
C8—C3—N2121.5 (2)C25—C24—C23120.1 (3)
C5—C4—C3120.9 (2)C25—C24—H24119.9
C5—C4—H4119.6C23—C24—H24119.9
C3—C4—H4119.6C24—C25—C26119.7 (3)
C4—C5—C6119.2 (2)C24—C25—H25120.1
C4—C5—H5120.4C26—C25—H25120.1
C6—C5—H5120.4C25—C26—C21121.0 (3)
C7—C6—C5121.3 (2)C25—C26—H26119.5
C7—C6—H6119.4C21—C26—H26119.5
C5—C6—H6119.4C32—C31—C36118.0 (2)
C6—C7—C8120.1 (2)C32—C31—C2122.5 (2)
C6—C7—H7119.9C36—C31—C2119.5 (2)
C8—C7—H7119.9C33—C32—C31120.9 (2)
N1—C8—C7123.5 (2)C33—C32—H32119.6
N1—C8—C3117.5 (2)C31—C32—H32119.6
C7—C8—C3119.0 (2)C33—C34—C35119.8 (2)
C16—C11—C12119.0 (2)C33—C34—H34120.1
C16—C11—N1120.7 (2)C35—C34—H34120.1
C12—C11—N1120.3 (2)C36—C35—C34120.1 (2)
C13—C12—C11120.1 (2)C36—C35—H35119.9
C13—C12—H12120.0C34—C35—H35119.9
C11—C12—H12120.0C35—C36—C31121.1 (2)
C12—C13—C14120.8 (2)C35—C36—H36119.5
C12—C13—H13119.6C31—C36—H36119.5
C14—C13—H13119.6C34—C33—C32120.0 (2)
C15—C14—C13119.2 (2)C34—C33—H33120.0
C15—C14—H14120.4C32—C33—H33120.0
C13—C14—H14120.4
C8—N1—C1—C240.5 (3)N1—C11—C12—C13−178.0 (2)
C11—N1—C1—C2−146.37 (19)C11—C12—C13—C14−0.2 (4)
C8—N1—C1—C21−82.7 (2)C12—C13—C14—C150.6 (4)
C11—N1—C1—C2190.5 (2)C13—C14—C15—C16−0.8 (4)
N1—C1—C2—N2−33.5 (3)C14—C15—C16—C110.6 (4)
C21—C1—C2—N293.0 (3)C12—C11—C16—C15−0.2 (4)
N1—C1—C2—C31149.66 (19)N1—C11—C16—C15177.9 (2)
C21—C1—C2—C31−83.8 (2)N1—C1—C21—C2224.1 (3)
C31—C2—N2—C3−176.7 (2)C2—C1—C21—C22−98.8 (3)
C1—C2—N2—C36.5 (3)N1—C1—C21—C26−156.4 (2)
C2—N2—C3—C4−168.5 (2)C2—C1—C21—C2680.7 (3)
C2—N2—C3—C816.2 (3)C26—C21—C22—C23−0.8 (4)
C8—C3—C4—C51.4 (4)C1—C21—C22—C23178.7 (2)
N2—C3—C4—C5−174.0 (2)C21—C22—C23—C240.9 (4)
C3—C4—C5—C60.1 (4)C22—C23—C24—C25−0.7 (4)
C4—C5—C6—C7−1.3 (4)C23—C24—C25—C260.5 (4)
C5—C6—C7—C80.9 (4)C24—C25—C26—C21−0.5 (4)
C11—N1—C8—C7−16.9 (3)C22—C21—C26—C250.6 (4)
C1—N1—C8—C7155.9 (2)C1—C21—C26—C25−178.9 (2)
C11—N1—C8—C3164.7 (2)N2—C2—C31—C32148.6 (2)
C1—N1—C8—C3−22.5 (3)C1—C2—C31—C32−34.5 (3)
C6—C7—C8—N1−177.7 (2)N2—C2—C31—C36−30.0 (3)
C6—C7—C8—C30.7 (3)C1—C2—C31—C36146.9 (2)
C4—C3—C8—N1176.6 (2)C36—C31—C32—C330.2 (3)
N2—C3—C8—N1−8.1 (3)C2—C31—C32—C33−178.4 (2)
C4—C3—C8—C7−1.8 (3)C33—C34—C35—C360.3 (4)
N2—C3—C8—C7173.5 (2)C34—C35—C36—C31−0.6 (4)
C8—N1—C11—C16139.9 (2)C32—C31—C36—C350.3 (3)
C1—N1—C11—C16−32.9 (3)C2—C31—C36—C35179.0 (2)
C8—N1—C11—C12−42.1 (3)C35—C34—C33—C320.2 (4)
C1—N1—C11—C12145.1 (2)C31—C32—C33—C34−0.5 (4)
C16—C11—C12—C130.0 (3)
Acknowledgements top

Financial support of this work by the Otto-von-Guericke-Universität Magdeburg is gratefully acknowledged.

references
References top

Bodforss, S. (1960). Liebigs Ann. Chem. 633, 66–77.

Kehrmann, F. & Messinger, J. (1891). Chem. Ber. 24, 1874–1876.

Lorenz, V., Thiele, K.-H. & Neumüller, B. (1994). Z. Anorg. Allg. Chem. 620, 691–696.

Sannicolò, F. (1983). J. Org. Chem. 48, 2924–2925.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.

Siegfied et al. (1892). [Please give full details for missing reference]

Stoe & Cie (1992). DIF4 and REDU4. Stoe & Cie, Darmstadt, Germany.