6-(3,5-Dimethyl-1H-pyrazol-1-yl)-1,2,4,5-tetra­zin-3(2H)-one

Kyrill Yu Suponitsky; Victor M Chernyshev; Anna G Mazharova; Nadezhda V Palysaeva; Aleksei B Sheremetev

doi:10.1107/S1600536813027360

. 2013 Oct 12;69(Pt 11):o1630–o1631. doi: 10.1107/S1600536813027360

6-(3,5-Dimethyl-1H-pyrazol-1-yl)-1,2,4,5-tetrazin-3(2H)-one

Kyrill Yu Suponitsky ^a,^*, Victor M Chernyshev ^b, Anna G Mazharova ^b, Nadezhda V Palysaeva ^c, Aleksei B Sheremetev ^c

PMCID: PMC3884301 PMID: 24454077

Abstract

The title compound, C₇H₈N₆O, represents the keto form and adopts a nearly planar structure (r.m.s. deviation of the non-H atoms = 0.072 Å). In the crystal, molecules form spiral chains along the c axis by N—H⋯N hydrogen bonds. The chains are linked to each other by weak C—H⋯O hydrogen bonds, forming a three-dimensional framework.

Related literature

For review on nucleophilic displacement at the 1,2,4,5-tetrazine ring, see: Clavier & Audebert (2010 ▶); Tolshchina et al. (2013 ▶). For the synthesis of 3-hydroxy-1,2,4,5-tetrazines, see: Ishmetova et al. (2009 ▶); Sheremetev et al. (2012a ▶,b ▶). For the structure of 3-hydroxy-1,2,4,5-tetrazine, see: Yeh et al. (1994 ▶). For a review on oxo-hydroxy tautomerism of various azines, see: Stanovnik et al. (2006 ▶). For standard bond lengths, see: Allen et al. (1987 ▶). graphic file with name e-69-o1630-scheme1.jpg

Experimental

Crystal data

C₇H₈N₆O
M _r = 192.19
Orthorhombic,
a = 12.1431 (11) Å
b = 12.6551 (12) Å
c = 5.3907 (5) Å
V = 828.40 (13) Å³
Z = 4
Mo Kα radiation
μ = 0.11 mm⁻¹
T = 120 K
0.28 × 0.22 × 0.20 mm

Data collection

Bruker APEXII CCD diffractometer
14157 measured reflections
1353 independent reflections
1228 reflections with I > 2σ(I)
R _int = 0.050

Refinement

R[F ² > 2σ(F ²)] = 0.037
wR(F ²) = 0.094
S = 1.05
1353 reflections
133 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.40 e Å⁻³
Δρ_min = −0.28 e Å⁻³

Data collection: APEX (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL, PLATON (Spek, 2009 ▶) and publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, New_Global_Publ_Block. DOI: 10.1107/S1600536813027360/kq2010sup1.cif

e-69-o1630-sup1.cif^{(19.6KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536813027360/kq2010Isup2.hkl

e-69-o1630-Isup2.hkl^{(66.8KB, hkl)}

Click here for additional data file.^{(4.1KB, cml)}

Supplementary material file. DOI: 10.1107/S1600536813027360/kq2010Isup3.cml

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
N4—H4⋯N1ⁱ	0.89 (3)	2.00 (3)	2.863 (2)	161 (3)
C2—H2A⋯O1ⁱⁱ	0.95	2.40	3.193 (3)	141

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

This work was supported financially by the Ministry of Education and Science of Russia through the Federal Target Program "Research and Educational Personnel of Innovative Russia at 2009–2013 Years" (grant No. 14.B37.21.0827), and, in part, by a Russian Foundation for Basic Research (grant No. 12–03-31346).

supplementary crystallographic information

1. Comment

Over the last decade, broad studies of nucleophilic displacemet at 1,2,4,5-tetrazine ring have demonstrated that the highly electron-withdrawing aromatic ring exhibit a rich diversity of chemical behavior, and today 3,6-bis(3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine 1 has become common precursor to various tetrazine derivatives (Clavier & Audebert, 2010; Tolshchina et al., 2013). The displacement of the dimethylpyrazolyl moiety in compound 1 by a wider range of N-nucleophiles has been well documented (Sheremetev et al., 2012a, 2012b), while reactions of the tetrazine 1 with O-nucleophiles have been studied to a lesser extent (Yeh et al., 1994; Ishmetova et al., 2009). Here, we wish to report the unexpected discovery of an unusual dimethylpyrazolyl moiety displacement of compound 1 when it is treated with N-nucleophile, such as 3-amino-1-tret-butyl-1,2,4-triazole 2.

Upon a refluxing of compound 1 with amine 2 and K₂CO₃ in acetonitrile and following treatment with water, an step required to workup of the reaction mixture, it was found that instead of introduction of N-nucleophile (with a formation of compound 3) the reaction gave the hydroxy derivative 4' (Figure 1).

According to X-ray data, the title compound adopts nearly planar structure (r.m.s. deviation of the non-hydrogen atoms is 0.072 Å) (Figure 2). In general, it can exist in two tautomeric forms (Stanovnik et al., 2006) as shown in Figure 1. The hydrogen atom H4 was localized and refined at the N4 nitrogen atom that means that the title compound exists in keto-form, and the equilibrium favors the tautomer 4'. This is also supproted by the bond length distribution in the tetrazin-3-one: the C7—O1 (1.215 (3) Å) bond corresponds to normal carbonyl bond (standard X-ray C═O value is in the range of 1.192–1.235 Å (Allen et al. 1987), while the N3—C6 (1.300 (2) Å) and N5—N6 (1.286 (2) Å) bonds are significantly shorter than the C7—N4 (1.368 (3) Å), N3—N4 (1.384 (2) Å), C6—N5 (1.377 (2) Å) and N6—C7 (1.427 (2) Å) bonds.

The crystal structure of 4' is stabilized by intermolecular N—H···N and C—H···O hydrogen bonds (Table 1). By means of the N4—H4···N1ⁱ hydrogen bond, molecules are connected into spiral chains along the c axis (Figure 3). Those chains are linked into 3D-framework (Figure 3) by the C2—H2A···O1ⁱⁱ contacts. Symmetry codes: (i) –x+2, –y+1, z+1/2; (ii) –x+3/2, y–1/2, z–3/2.

2. Experimental

The X-ray quality crystals of the title compound were grown by slow evaporation of acetonitrile solution.

All the reagents were of analytical grade, purchased from commercial sources, and used as received. Infrared spectra were determined in KBr pellets on a Perkin-Elmer Model 577 spectrometer. Mass-spectra were recorded on a Varian MAT-311 A instrument. The ¹H, ¹³C and ¹⁵N NMR spectra (external standard: CH₃NO₂) were recorded at 300.13, 75.47 and 50.7 MHz, respectively. The chemical shift values (δ, p.p.m.) are expressed relative to the chemical shift of the solvent-d or to external standard without correction nitromethane (¹⁴N and ¹⁵N). Melting points were determined on Gallenkamp melting point apparatus and are uncorrected.

6-(3,5-Dimethyl-1H-pyrazol-1-yl)-1,2,4,5-tetrazin-3(2H)-one (4'). A mixture of 3,6-bis(3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine 1 (0.27 g, 1 mmol), 3-amino-1-tretbutyl-1,2,4-triazole 2 (0.14 g, 1 mmol), and K₂CO₃ (0.14 g, 1 mmol) was refluxed in dry acetonitrile (10 mL) for 3 d. The reaction mixture was then cooled and a violet solid formed was collected by filtration. The solid was dissolved in water (10 mL), acidifed with 3% HCl to pH 1 and cooled to 278 K. A solid was collected by filtration, washed with 1% HCl and hexane and crystallized from MeCN/H₂O, yield 0.15 g (82%), mp 483–484 K (dec.); IR (KBr, cm^-1): ν = 3135–2823, 1744, 1706, 1693, 1553, 1506, 1435, 1405, 1373, 1263, 1161, 1138, 1105, 1063, 1025, 993, 975, 836, 808. ¹H MNR (DMSO-d₃, 293 K): δ = 2.20 and 2.38 (3H+3H, C1—CH₃ and C3—CH₃), 6.17 (c, 1H, CH), 8.51 (br, 1H, OH); ¹³C MNR (DMSO-d₃, 293 K): δ = 13.3, 13.2, 108.9, 141.9, 147.7, 150.7, 152.0. ¹⁵N MNR (DMSO-d₃, 293 K): δ = –1.87, –35.0, –77.6, –173.3. Anal. Calcd. for C₇H₈N₆O (192.17): C, 43.75; H, 4.20; N, 43.73. Found: C, 43.81; H, 4.24; N, 43.61.