6-Methyl-N-(2-methyl­phen­yl)-3-phenyl-1,6-dihydro-1,2,4,5-tetra­zine-1-carbox­amide

Feng Xu; Weixiao Hu

doi:10.1107/S1600536808020199

. 2008 Jul 9;64(Pt 8):o1432. doi: 10.1107/S1600536808020199

6-Methyl-N-(2-methylphenyl)-3-phenyl-1,6-dihydro-1,2,4,5-tetrazine-1-carboxamide

Feng Xu ^a, Weixiao Hu ^a,^*

PMCID: PMC2962064 PMID: 21203148

Abstract

In the title compound, C₁₇H₁₆N₅O, the central tetrazine ring adopts an unsymmetrical boat conformation with the two C atoms as flagpoles. This compound can be considered as having homoaromaticity. The crystal structure is stabilized by intermolecular C—H⋯O interactions between a benzene H atom and the carbonyl O atom.

Related literature

For related literature, see: Hu et al. (2004 ▶, 2005 ▶); Jennison et al. (1986 ▶); Sauer (1996 ▶); Stam et al. (1982 ▶); Xu et al. (2006 ▶).

Experimental

Crystal data

C₁₇H₁₆N₅O
M _r = 306.35
Monoclinic,
a = 13.941 (6) Å
b = 5.675 (2) Å
c = 20.614 (8) Å
β = 102.055 (6)°
V = 1594.9 (11) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 291 (2) K
0.12 × 0.10 × 0.06 mm

Data collection

Bruker SMART APEX CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.980, T _max = 0.995
6815 measured reflections
3116 independent reflections
1882 reflections with I > 2σ(I)
R _int = 0.084

Refinement

R[F ² > 2σ(F ²)] = 0.072
wR(F ²) = 0.193
S = 0.94
3116 reflections
226 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.54 e Å⁻³
Δρ_min = −0.31 e Å⁻³

Data collection: SMART (Bruker, 2005 ▶); cell refinement: SAINT (Bruker, 2005 ▶); data reduction: SAINT; 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: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808020199/lx2060sup1.cif

e-64-o1432-sup1.cif^{(18.8KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808020199/lx2060Isup2.hkl

e-64-o1432-Isup2.hkl^{(152.9KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C6—H6⋯Oⁱ	0.93	2.56	3.385 (3)	148

Open in a new tab

Symmetry code: (i) Inline graphic .

Acknowledgments

The authors are very grateful to the National Natural and Scientific Foundation (grant No. 20272053) for financial support.

supplementary crystallographic information

Comment

1,2,4,5-Tetrazine derivatives have high potential for biological activity, possessing a wide spectrum of antiviral and antitumor properties. They have been widely used in pesticides and herbicides (Sauer, 1996). Dihydro-1,2,4,5-tetrazine has four isomers, namely 1,2-, 1,4-, 1,6-, and 3,6-dihydro-1,2,4,5-tetrazines. The 1,6-dihydro structures (Stam et al., 1982; Jennison et al., 1986) were found, by X-ray diffraction, to be homoaromatic. In continuation of our work on the structure–activity relationship of 1,6-dihydro-1,2,4,5-tetrazine derivatives (Hu et al., 2004, 2005), we report the crystal structure of the title compound (I) (Fig. 1).

In the tetrazine ring, atoms N1, N2, N3 and N4 are coplanar, while atoms C1 and C2 deviate from the plane by 0.597 (3) and 0.225 (3)°, respectively. The N1/C1/N4 and N2/C3/N3 planes make dihedral angles of 42.3 (2)° and 19.7 (2)°, respectively, with the N1–N4 plane, i.e. the tetrazine ring adopts an unsymmetrical boat conformation. The C3–C8 benzene ring make dihedral angles of 13.2 (1)°, with the N1–N4 plane. N1 is almost sp² hybridized due to the angles around it add up to 359.6 (2)°. In keeping with similar situations in 3-phenyl-6-ethyl-1,6-dihydro-1,2,4,5-tetrazine (Stam et al., 1982), 3-(p-chlorophenyl)-6-methyl-1,6-dihydro-1,2,4,5-tetrazine (Xu et al., 2006) and 1-acetyl-3,6-dimethyl-1,2,4,5-tetrazine (Jennison et al., 1986), it can be considered that the molecule is homoaromatic.

The Fig. 2 shows that intramolecular C—H···O hydrogen bonds form a pseudo-five-membered ring. The crystal packing (Fig. 2) is stabilized by intermolecular C—H···O interactions between a benzene H atom and the O atom of carbonyl group, with a C6—H6···Oⁱ separation of 3.385 (3) Å (Table 1; symmetry code as in Fig. 2).

Experimental

6-methyl-3-phenyl-1,6-dihydro-1,2,4,5-tetrazine (3.0 mmol), chloroform (10 ml) and pyridine (0.25 ml, 3.1 mmol) were mixed. 1-isocyanato-2-methylbenzene (3.0 mmol) in chloroform (10 ml) was added dropwise with stirring at room temperature. After the starting 1,6-dihydro-1,2,4,5-tetrazine was completely consumed (the reaction courses was monitored by TLC, dichloromethane system), evaporation of the chloroform, crude N-(o-methylphenyl) 3-phenyl-6-methyl-1,6-dihydro-1,2,4,5-tetrazine-1-carboxamide was obtained and purified by preparative thin-layer chromatography over silica gel PF254 (2 mm) (dichloromethane:petroleum ether = 1:1). The solution of the compound in anhydrous ethanol was concentrated gradually at room temperature to afford single crystals, which was suitable for X-ray diffraction. m.p. 378–380 K. Spectroscopic analysis: ¹H NMR (CDCl₃) δ p.p.m.: 8.64 (s, 1H), 8.14–8.16 (m, 2H, ArH), 7.92 (d, 1H, J = 8.0 Hz), 7.52–7.55 (m, 3H, ArH), 7.22 (m, 2H, ArH), 7.08 (t, 1H, J = 7.2 Hz), 6.91 (q, 1H, J=6.4 Hz), 2.34 (s, 3H), 1.09 (d, 3H, J = 6.8 Hz).