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Oxidative cyclization of 5-ethyl-3-(4-methoxy­benzyl­idene)­hydrazino-1,2,4-triazino­[5,6-b]­indole gave the linearly annel­ated title compound, C19H16N6O. The skeleton is approx­imately planar, except for the ethyl group.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S010827010001194X/qd0026sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S010827010001194X/qd0026Isup2.hkl
Contains datablock I

CCDC reference: 152674

Comment top

Vauable medicinal applications and biological activities are known to be associated with the 1,2,4-triazolo-1,2,4-triazino[5,6-b]indole structure (Katz & Margalith, 1984). One of the synthetic pathways to obtain the 10-substituted derivatives of these compounds is the oxidative cyclization of 5-substituted-3-alkylidene- and 3-arylidenehydrazino-1,2,4-triazino[5,6-b]indoles (Shaban et al., 1993, 1999, 2000; Rashed et al., 1998). Assignment of structures to the obtained products was inconclusive whether they are the linearly annelated 1,2,4-triazolo[4',3':2,3]1,2,4-triazino[5,6-b]indoles such as the title compound, (I), (Shaban et al., 1993, 1999, 2000) or the angular-annelated 1,2,4-triazolo[3',4':3,4]-1,2,4-triazino[5,6-b]indole regioisomers, (II) (Holla & Udupa, 1990; Rashed et al., 1998). The present work has been initiated to settle this contradiction. The title compound, (I), was prepared by oxidative cyclization of 3-(4-methoxybenzylidene)hydrazino-1,2,4-triazino[5,6-b]indole with 10% ethanolic iron(III) chloride, thionyl chloride or 30% aqueous sodium hypochlorite in dioxane. The determined molecular structure revealed that the four-ring system corresponds to the linearly annelated structure (I) and not the angularly annelated structure (II). The skeleton is approximately planar except for the ethyl group. Bond distances showed localization of the N2—C8 and N3—C7 π bonds of the 1,2,4-trizole ring as well as N5—C9 and N6—C10 π bonds of the 1,2,4-triazine ring.

Experimental top

The title compound can be synthesized in three different ways (a-c): (a) a suspension of 5-ethyl-3-(4-methoxybenzylidene)hydrazino-1,2,4-triazino[5,6-b]indole (0.664 g, 2 mmol) in toluene (30 ml) was treated with 10% ethanolic iron(III) chloride solution (20 ml) and heated at reflux for 3 h. The mixture was evaporated to dryness and the obtained orange residue was triturated with water, filtered, washed with water, dried and crystallized from ethanol (yield 39%, m.p. 585 K). (b) A mixture of the aforementioned hydrazone (0,664 g, 2 mmol) and thionyl chloride (25 ml) was heated at reflux for 5 h. The mixture was evaporated and the obtained residue was crystallized from ethanol (yield 45%, m.p. 585 K). (c) A suspension of the same aforementioned hydrazone (0.664 g, 2 mmol) in dioxane (5 ml) was treated with 30% aqueous sodium hypochlorite solution (15 ml) and heated at 373 K for 10 min. After attaining ambient temperature, the product was filtered, washed with water, dried, and crystallized from ethanol (yield 52%, m.p. 585 K).

Refinement top

The low fraction of observed reflections with I > 2σ(I) to the total number of measured reflections, 1005/2935 for 2θmax = 50°, was due to the weak high-order reflections. If the original data is cut off at 2θ = 45°, the ratio of observed/total improves to 953/2171.

Computing details top

Data collection: CAD-4-PC Software (Enraf-Nonius, 1989); cell refinement: CAD-4-PC; data reduction: NRCVAX DATRD2 (Le Page & Gabe, 1979); program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: SHELXL93 (Sheldrick, 1993).

10-Ethyl-3-(4-methoxyphenyl)-1,2,4-triazolo[4'3':2,3]1,2,4- triazino[5,6-b]indole top
Crystal data top
C19H16N6OZ = 2
Mr = 344.38F(000) = 360
Triclinic, P1Dx = 1.371 Mg m3
a = 9.420 (3) ÅMo Kα radiation, λ = 0.71073 Å
b = 9.805 (4) ÅCell parameters from 25 reflections
c = 11.228 (6) Åθ = 3.0–16.5°
α = 114.55 (4)°µ = 0.09 mm1
β = 114.67 (4)°T = 293 K
γ = 91.03 (3)°Plate, orange
V = 834.0 (8) Å30.50 × 0.31 × 0.07 mm
Data collection top
Enraf-Nonius CAD-4
diffractometer
Rint = 0.000
ω–2θ scansθmax = 25.0°
Absorption correction: ψ scan
(NRCVAX ABSORP; Gabe et al., 1989)
h = 1111
Tmin = 0.777, Tmax = 0.996k = 011
2935 measured reflectionsl = 1313
2935 independent reflections3 standard reflections every 240 min
1005 reflections with I > 2σ(I) intensity decay: 1.3%
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) = 0.115H-atom parameters constrained
S = 0.83 w = 1/[σ2(Fo2) + (0.0706P)2]
where P = (Fo2 + 2Fc2)/3
2935 reflections(Δ/σ)max = 0.005
235 parametersΔρmax = 0.19 e Å3
0 restraintsΔρmin = 0.24 e Å3
Crystal data top
C19H16N6Oγ = 91.03 (3)°
Mr = 344.38V = 834.0 (8) Å3
Triclinic, P1Z = 2
a = 9.420 (3) ÅMo Kα radiation
b = 9.805 (4) ŵ = 0.09 mm1
c = 11.228 (6) ÅT = 293 K
α = 114.55 (4)°0.50 × 0.31 × 0.07 mm
β = 114.67 (4)°
Data collection top
Enraf-Nonius CAD-4
diffractometer
1005 reflections with I > 2σ(I)
Absorption correction: ψ scan
(NRCVAX ABSORP; Gabe et al., 1989)
Rint = 0.000
Tmin = 0.777, Tmax = 0.9963 standard reflections every 240 min
2935 measured reflections intensity decay: 1.3%
2935 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0530 restraints
wR(F2) = 0.115H-atom parameters constrained
S = 0.83Δρmax = 0.19 e Å3
2935 reflectionsΔρmin = 0.24 e Å3
235 parameters
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 on F2 for ALL reflections except for 0 with very negative F2 or flagged by the user for potential systematic errors. 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
O10.2446 (4)0.3329 (3)0.3136 (3)0.0725 (9)
N10.1436 (3)0.6069 (3)0.1793 (3)0.0524 (9)
N20.3057 (3)0.3585 (3)0.0108 (3)0.0503 (9)
N30.0058 (3)0.2897 (3)0.0251 (3)0.0418 (8)
N40.1388 (3)0.1865 (3)0.0751 (3)0.0417 (8)
N50.4024 (4)0.0917 (4)0.1913 (4)0.0606 (10)
N60.3248 (4)0.0222 (3)0.2422 (3)0.0564 (10)
C10.0214 (4)0.6701 (4)0.2675 (4)0.0471 (11)
C20.0996 (5)0.8177 (4)0.3845 (4)0.0609 (12)
H20.04290.89030.41360.073*
C30.2644 (5)0.8511 (5)0.4547 (4)0.0660 (13)
H30.31980.94900.53310.079*
C40.3526 (5)0.7435 (5)0.4132 (4)0.0644 (13)
H40.46430.77060.46430.077*
C50.2740 (4)0.5973 (4)0.2964 (4)0.0534 (11)
H50.33110.52510.26760.064*
C60.1075 (4)0.5617 (4)0.2236 (4)0.0403 (10)
C70.0119 (4)0.4235 (4)0.1048 (4)0.0389 (10)
C80.1666 (4)0.4570 (4)0.0838 (4)0.0426 (10)
C90.2880 (4)0.2163 (4)0.0908 (4)0.0493 (11)
C100.1707 (4)0.0326 (4)0.1744 (4)0.0462 (11)
C110.0529 (4)0.0537 (4)0.2007 (4)0.0444 (10)
C120.1101 (4)0.0048 (4)0.1304 (4)0.0566 (12)
H120.15180.10700.05730.068*
C130.2153 (5)0.0829 (4)0.1643 (4)0.0621 (12)
H130.32500.03990.11510.074*
C140.1534 (5)0.2355 (4)0.2728 (4)0.0543 (12)
C150.0082 (5)0.2966 (4)0.3430 (4)0.0634 (13)
H150.04950.39920.41510.076*
C160.1107 (5)0.2080 (4)0.3080 (4)0.0551 (12)
H160.22010.25180.35690.066*
C170.4115 (5)0.2754 (5)0.2433 (6)0.091 (2)
H17A0.46050.35570.28250.136*
H17B0.45420.23980.13880.136*
H17C0.43380.19140.26060.136*
C180.2738 (5)0.6873 (5)0.1877 (5)0.0790 (15)
H18A0.24210.79150.20550.095*
H18B0.36960.63490.09270.095*
C190.3139 (6)0.6951 (6)0.3044 (5)0.103 (2)
H19A0.39860.74840.30300.154*
H19B0.22070.74930.39940.154*
H19C0.34830.59260.28640.154*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.082 (2)0.049 (2)0.094 (2)0.021 (2)0.055 (2)0.026 (2)
N10.041 (2)0.043 (2)0.063 (2)0.017 (2)0.027 (2)0.012 (2)
N20.045 (2)0.042 (2)0.050 (2)0.008 (2)0.017 (2)0.013 (2)
N30.039 (2)0.041 (2)0.038 (2)0.007 (2)0.013 (2)0.017 (2)
N40.035 (2)0.035 (2)0.038 (2)0.000 (2)0.008 (2)0.012 (2)
N50.048 (2)0.050 (2)0.062 (2)0.002 (2)0.016 (2)0.017 (2)
N60.047 (2)0.041 (2)0.056 (2)0.001 (2)0.014 (2)0.011 (2)
C10.044 (2)0.043 (3)0.045 (3)0.003 (2)0.022 (2)0.013 (2)
C20.062 (3)0.043 (3)0.059 (3)0.012 (2)0.025 (2)0.011 (2)
C30.066 (3)0.051 (3)0.045 (3)0.005 (2)0.017 (2)0.001 (2)
C40.051 (3)0.064 (3)0.051 (3)0.003 (2)0.013 (2)0.014 (3)
C50.054 (3)0.040 (3)0.047 (3)0.006 (2)0.016 (2)0.011 (2)
C60.038 (2)0.038 (2)0.030 (2)0.002 (2)0.010 (2)0.009 (2)
C70.034 (2)0.041 (3)0.038 (2)0.008 (2)0.016 (2)0.016 (2)
C80.045 (3)0.038 (2)0.042 (3)0.010 (2)0.021 (2)0.015 (2)
C90.041 (2)0.050 (3)0.040 (3)0.001 (2)0.011 (2)0.014 (2)
C100.051 (3)0.032 (2)0.042 (3)0.003 (2)0.014 (2)0.014 (2)
C110.049 (2)0.035 (2)0.038 (2)0.004 (2)0.015 (2)0.013 (2)
C120.055 (3)0.029 (2)0.058 (3)0.003 (2)0.014 (2)0.009 (2)
C130.058 (3)0.045 (3)0.069 (3)0.011 (2)0.026 (2)0.018 (3)
C140.065 (3)0.041 (3)0.058 (3)0.014 (2)0.031 (2)0.022 (2)
C150.079 (3)0.032 (2)0.057 (3)0.006 (2)0.033 (3)0.002 (2)
C160.058 (3)0.049 (3)0.044 (3)0.002 (2)0.019 (2)0.015 (2)
C170.089 (4)0.065 (3)0.148 (5)0.029 (3)0.079 (4)0.051 (3)
C180.079 (3)0.067 (3)0.075 (4)0.018 (2)0.027 (3)0.029 (3)
C190.109 (4)0.127 (5)0.104 (5)0.039 (3)0.075 (4)0.054 (4)
Geometric parameters (Å, º) top
O1—C141.363 (4)C1—C61.401 (4)
O1—C171.405 (4)C2—C31.373 (5)
N1—C81.357 (4)C3—C41.402 (5)
N1—C11.396 (4)C4—C51.383 (5)
N1—C181.485 (4)C5—C61.386 (4)
N2—C81.311 (4)C6—C71.439 (4)
N2—C91.368 (4)C7—C81.442 (4)
N3—C71.307 (4)C10—C111.461 (5)
N3—N41.368 (4)C11—C121.375 (5)
N4—C101.384 (4)C11—C161.394 (4)
N4—C91.394 (4)C12—C131.392 (5)
N5—C91.311 (4)C13—C141.387 (5)
N5—N61.398 (4)C14—C151.368 (5)
N6—C101.298 (4)C15—C161.380 (5)
C1—C21.392 (5)C18—C191.482 (5)
C14—O1—C17118.3 (3)N3—C7—C8123.2 (3)
C8—N1—C1108.5 (3)C6—C7—C8107.0 (3)
C8—N1—C18125.0 (3)N2—C8—N1125.9 (3)
C1—N1—C18126.6 (3)N2—C8—C7125.6 (3)
C8—N2—C9111.6 (3)N1—C8—C7108.5 (3)
C7—N3—N4111.6 (3)N5—C9—N2127.0 (4)
N3—N4—C10129.3 (3)N5—C9—N4110.4 (3)
N3—N4—C9125.3 (3)N2—C9—N4122.6 (3)
C10—N4—C9105.3 (3)N6—C10—N4108.0 (3)
C9—N5—N6105.5 (3)N6—C10—C11125.6 (3)
C10—N6—N5110.8 (3)N4—C10—C11126.4 (3)
C2—C1—N1128.3 (4)C12—C11—C16117.1 (3)
C2—C1—C6121.3 (3)C12—C11—C10125.6 (3)
N1—C1—C6110.5 (3)C16—C11—C10117.3 (3)
C3—C2—C1116.8 (4)C11—C12—C13122.6 (3)
C2—C3—C4122.7 (4)C14—C13—C12118.8 (4)
C5—C4—C3120.1 (4)O1—C14—C15116.3 (4)
C4—C5—C6118.1 (3)O1—C14—C13124.0 (4)
C5—C6—C1121.0 (3)C15—C14—C13119.6 (4)
C5—C6—C7133.5 (3)C14—C15—C16120.8 (4)
C1—C6—C7105.4 (3)C15—C16—C11121.1 (4)
N3—C7—C6129.7 (3)C19—C18—N1114.4 (4)

Experimental details

Crystal data
Chemical formulaC19H16N6O
Mr344.38
Crystal system, space groupTriclinic, P1
Temperature (K)293
a, b, c (Å)9.420 (3), 9.805 (4), 11.228 (6)
α, β, γ (°)114.55 (4), 114.67 (4), 91.03 (3)
V3)834.0 (8)
Z2
Radiation typeMo Kα
µ (mm1)0.09
Crystal size (mm)0.50 × 0.31 × 0.07
Data collection
DiffractometerEnraf-Nonius CAD-4
diffractometer
Absorption correctionψ scan
(NRCVAX ABSORP; Gabe et al., 1989)
Tmin, Tmax0.777, 0.996
No. of measured, independent and
observed [I > 2σ(I)] reflections
2935, 2935, 1005
Rint0.000
(sin θ/λ)max1)0.594
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.053, 0.115, 0.83
No. of reflections2935
No. of parameters235
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.19, 0.24

Computer programs: CAD-4-PC Software (Enraf-Nonius, 1989), CAD-4-PC, NRCVAX DATRD2 (Le Page & Gabe, 1979), SHELXS86 (Sheldrick, 1990), SHELXL93 (Sheldrick, 1993).

Selected geometric parameters (Å, º) top
O1—C141.363 (4)N4—C101.384 (4)
O1—C171.405 (4)N4—C91.394 (4)
N1—C81.357 (4)N5—C91.311 (4)
N1—C11.396 (4)N5—N61.398 (4)
N1—C181.485 (4)N6—C101.298 (4)
N2—C81.311 (4)C1—C61.401 (4)
N2—C91.368 (4)C6—C71.439 (4)
N3—C71.307 (4)C7—C81.442 (4)
N3—N41.368 (4)C10—C111.461 (5)
C14—O1—C17118.3 (3)C1—C6—C7105.4 (3)
C8—N1—C1108.5 (3)N3—C7—C6129.7 (3)
C8—N1—C18125.0 (3)N3—C7—C8123.2 (3)
C1—N1—C18126.6 (3)C6—C7—C8107.0 (3)
C8—N2—C9111.6 (3)N2—C8—N1125.9 (3)
C7—N3—N4111.6 (3)N2—C8—C7125.6 (3)
N3—N4—C10129.3 (3)N1—C8—C7108.5 (3)
N3—N4—C9125.3 (3)N5—C9—N2127.0 (4)
C10—N4—C9105.3 (3)N5—C9—N4110.4 (3)
C9—N5—N6105.5 (3)N2—C9—N4122.6 (3)
C10—N6—N5110.8 (3)N6—C10—N4108.0 (3)
C2—C1—N1128.3 (4)N6—C10—C11125.6 (3)
N1—C1—C6110.5 (3)N4—C10—C11126.4 (3)
C5—C6—C7133.5 (3)
 

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