5-Bromo-1,2,4-triazolo[1,5-a]pyrimidine

Gilandoust, M.; Harsha, K.B.; Madan Kumar, S.; Rakesh, K.S.; Lokanath, N.K.; Byrappa, K.; Rangappa, K.S.

doi:10.1107/S2414314616019441

organic compounds

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ISSN: 2414-3146

Volume 1| Part 12| December 2016| x161944

https://doi.org/10.1107/S2414314616019441

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5-Bromo-1,2,4-triazolo[1,5-a]pyrimidine

Maryam Gilandoust,^a K. B. Harsha,^a S. Madan Kumar,^b K. S. Rakesh,^a N. K. Lokanath,^c K. Byrappa ^d and K. S. Rangappa ^a ^*

^aDepartment of Studies in Chemistry, Manasagangotri, University of Mysore, Mysore, Karnataka, India, ^bPURSE Lab, Mangalagangotri, Mangalore University, Mangaluru 574 199, India, ^cDepartment of Studies in Physics, Manasagangotri, University of Mysore, Mysore, Karnataka, India, and ^dDepartment of Material Science, Mangalore University, Mangaluru 574 199, India
^*Correspondence e-mail: rangappaks@gmail.com

Edited by J. Simpson, University of Otago, New Zealand (Received 23 November 2016; accepted 5 December 2016; online 13 December 2016)

In the title compound, C₅H₃BrN₄, the almost planar triazolopyrimidine ring system (r.m.s. deviation = 0.014 Å) carries a bromo substituent at the 5-position. In the crystal, C—H⋯N hydrogen bonds form inversion dimers enclosing R₂²(8) rings and also link molecules into C(5) chains along the c-axis direction. Br⋯N halogen bonds [3.185 (4) Å], π–π stacking interactions, centroid-to-centroid separation [3.663 (3) Å] and C—Br⋯π contacts [Br⋯Cg = 3.7881 (17) Å] are also found and combine with the C—H⋯N hydrogen bonds to stack the molecules along the a-axis direction.

Keywords: crystal structure; triazolo[1,5-a]pyrimidine derivatives; hydrogen bonds; Br⋯N halogen bonds; π–π stacking interactions.

CCDC reference: 1520692

Structure description

In a continuation of our work on the synthesis and structure determination of 1,2,4-triazolo[1,5-a]pyrimidine derivatives (Gilandoust et al., 2016 ), the title compound was prepared and its structure is reported here, Fig. 1. The triazolopyrimidine ring system is planar (as expected) with an r.m.s. deviation of 0.014 Å. Bond lengths and angles in the ring system are normal and similar to those found in the related compound 5-(2-ethoxy-4-fluorophenyl-1,2,4-triazolo[1,5-a]pyrimidine (Gilandoust et al., 2016).

Figure 1
A view of the title molecule, showing the atom labelling. Displacement ellipsoids are drawn at the 50% probability level.

In the crystal, C5—H5⋯N3 contacts, Table 1, form inversion dimers and generate R₂²(6) rings. C1—H1⋯N1 hydrogen bonds form C(5) chains of molecules along c. These contacts combine with Br1⋯N4ⁱⁱⁱ halogen bonds [d(Br⋯N) = 3.185 (4) Å; symmetry code: (iii) −x + $[{1\over 2}]$ , y + $[{1\over 2}]$ ,-z + $[{3\over 2}]$ ] to form stacked layers of molecules in the bc plane, Fig. 2. Stacking along the a-axis direction is aided further by a combination of offset π–π stacking interactions [Cg1⋯Cg2^iv = 3.663 (3) Å; symmetry code: (iv) −1 + x, y, z; Cg1 and Cg2 are the centroids of the C4/N2/N3/C5/N4 and C1–C3/N1/C4/N2 rings, respectively] reinforced by unusual, but not unprecedented (Shukla et al., 2017 ), C3—Br1⋯Cg2^v contacts [Br⋯Cg1 = 3.7881 (17) Å, C3—Br1⋯Cg2 = 67.60 (12)°; symmetry code: (v) x + 1, y, z;] , Fig. 3. Overall, a three-dimensional network of molecules stacked along the a-axis direction forms as a result of these contacts, Fig. 4.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1⋯N1ⁱ	0.93	2.52	3.421 (6)	164
C5—H5⋯N3ⁱⁱ	0.93	2.61	3.321 (6)	133
Symmetry codes: (i) $[x-{\script{1\over 2}}, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (ii) -x-1, -y, -z+2.

Figure 2
Layers of molecules in the bc plane. Hydrogen and halogen bonds are drawn as blue dashed lines.

Figure 3
Offset π–π contacts and C—Br⋯π interactions (green dotted lines), with ring centroids shown as coloured spheres.

Figure 4
The overall packing, viewed along the a axis, showing π–π contacts and C—Br⋯π interactions.

Synthesis and crystallization

5-Bromo-2-hydrazinopyrimidine (0.95 mmol) and formaldehyde (1.00 mmol) were suspended in EtOH (5 ml), and stirred for 2 h at RT. The reaction mixture was concentrated under reduced pressure to remove the ethanol and the crude product purified by column chromatography using 60:120 mesh silica gel and a MeOH: dichloromethane solution (10:90 ml) as eluent to yield 5-bromo-2-(2-methylenehydrazinyl) pyrimidine as a beige solid. 5-Bromo-2-(2-methylenehydrazinyl)pyrimidine (0.78 mmol) dissolved in (5 ml) dichloromethane and iodobenzene diacetate (0.78 mmol) was added in one portion. The mixture was stirred for 15 h at RT and the solvent evaporated. The residue was titurated with Et₂O (5 ml), filtered and chromatographed using 60:120 mesh silica gel and MeOH:dichloromethane (10:90 ml) as eluent to give 5-bromo-[1,2,4]triazolo[1,5-a]pyrimidine as a yellow solid. Good quality single crystals suitable for X-ray diffraction studies were obtained by the slow evaporation method using ethanol as solvent.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2.

Table 2
Experimental details

Crystal data
Chemical formula	C₅H₃BrN₄
M_r	199.02
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	293
a, b, c (Å)	3.9511 (4), 14.3306 (11), 11.367 (1)
β (°)	94.574 (8)
V (Å³)	641.57 (9)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	6.32
Crystal size (mm)	0.31 × 0.24 × 0.23

Data collection
Diffractometer	Rigaku Saturn724+
Absorption correction	Multi-scan (NUMABS; Rigaku, 1999 )
T_min, T_max	0.244, 0.323
No. of measured, independent and observed [I > 2σ(I)] reflections	2438, 1129, 977
R_int	0.036
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.041, 0.111, 1.08
No. of reflections	1129
No. of parameters	92
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.78, −0.48
Computer programs: CrystalClear SM Expert (Rigaku, 2011 ), SHELXS97 (Sheldrick, 2008 ), SHELXL2014 (Sheldrick, 2015 ), Mercury (Macrae et al., 2008 ) and OLEX2 (Dolomanov et al., 2009 ).

Structural data

CCDC reference: 1520692

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314616019441/sj4072sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314616019441/sj4072Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314616019441/sj4072Isup3.cml

checkCIF report

Computing details top

Data collection: CrystalClear SM Expert (Rigaku, 2011); cell refinement: CrystalClear SM Expert (Rigaku, 2011); data reduction: CrystalClear SM Expert (Rigaku, 2011); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

5-Bromo-1,2,4-triazolo[1,5-a]pyrimidine top

Crystal data top

C₅H₃BrN₄	F(000) = 384
M_r = 199.02	D_x = 2.060 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
a = 3.9511 (4) Å	Cell parameters from 1129 reflections
b = 14.3306 (11) Å	θ = 2.3–25.0°
c = 11.367 (1) Å	µ = 6.32 mm⁻¹
β = 94.574 (8)°	T = 293 K
V = 641.57 (9) Å³	Colourless, block
Z = 4	0.31 × 0.24 × 0.23 mm

Data collection top

Rigaku Saturn724+ diffractometer	977 reflections with I > 2σ(I)
profile data from ω–scans	R_int = 0.036
Absorption correction: multi-scan (NUMABS; Rigaku, 1999)	θ_max = 25.0°, θ_min = 2.3°
T_min = 0.244, T_max = 0.323	h = −4→3
2438 measured reflections	k = −16→17
1129 independent reflections	l = −13→12

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.041	w = 1/[σ²(F_o²) + (0.0649P)² + 0.2378P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.111	(Δ/σ)_max = 0.001
S = 1.08	Δρ_max = 0.78 e Å⁻³
1129 reflections	Δρ_min = −0.48 e Å⁻³
92 parameters	Extinction correction: SHELXL2014 (Sheldrick, 2015), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.017 (4)
Primary atom site location: iterative

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Br1	0.37251 (12)	0.44459 (3)	0.83589 (4)	0.0390 (3)
N2	−0.1257 (9)	0.1890 (2)	0.9772 (3)	0.0275 (8)
N1	0.1085 (9)	0.2690 (2)	0.8197 (3)	0.0291 (8)
N3	−0.2878 (11)	0.1067 (3)	0.9961 (3)	0.0381 (10)
N4	−0.1505 (10)	0.1167 (3)	0.8052 (3)	0.0360 (10)
C2	0.1125 (11)	0.3336 (3)	1.0154 (4)	0.0322 (10)
H2	0.1769	0.3830	1.0655	0.039*
C3	0.1746 (10)	0.3359 (3)	0.8956 (3)	0.0255 (9)
C1	−0.0434 (12)	0.2578 (3)	1.0557 (4)	0.0347 (11)
H1	−0.0924	0.2530	1.1341	0.042*
C4	−0.0482 (11)	0.1944 (3)	0.8616 (3)	0.0241 (9)
C5	−0.2909 (13)	0.0680 (3)	0.8910 (4)	0.0365 (11)
H5	−0.3859	0.0093	0.8763	0.044*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.0447 (4)	0.0354 (4)	0.0366 (4)	−0.00695 (19)	0.0006 (2)	0.00610 (18)
N2	0.0334 (19)	0.0306 (19)	0.0184 (17)	−0.0009 (16)	0.0018 (15)	0.0026 (15)
N1	0.037 (2)	0.031 (2)	0.0200 (18)	0.0021 (16)	0.0045 (16)	0.0020 (15)
N3	0.058 (3)	0.031 (2)	0.025 (2)	−0.0082 (19)	0.0050 (18)	0.0059 (16)
N4	0.053 (3)	0.030 (2)	0.0250 (19)	−0.0032 (18)	0.0038 (18)	−0.0064 (16)
C2	0.042 (3)	0.030 (2)	0.023 (2)	−0.002 (2)	−0.0011 (19)	−0.0063 (18)
C3	0.022 (2)	0.032 (2)	0.023 (2)	0.0001 (17)	−0.0014 (16)	0.0024 (17)
C1	0.052 (3)	0.039 (3)	0.014 (2)	−0.001 (2)	0.004 (2)	−0.0020 (18)
C4	0.031 (2)	0.026 (2)	0.0147 (18)	0.0048 (18)	−0.0008 (16)	−0.0004 (16)
C5	0.042 (3)	0.030 (2)	0.036 (3)	−0.006 (2)	−0.005 (2)	−0.001 (2)

Geometric parameters (Å, º) top

Br1—C3	1.893 (4)	N4—C4	1.331 (6)
N2—N3	1.367 (5)	N4—C5	1.354 (6)
N2—C1	1.353 (5)	C2—H2	0.9300
N2—C4	1.375 (5)	C2—C3	1.403 (6)
N1—C3	1.303 (5)	C2—C1	1.347 (6)
N1—C4	1.342 (5)	C1—H1	0.9300
N3—C5	1.316 (6)	C5—H5	0.9300

N3—N2—C4	110.0 (3)	C2—C3—Br1	118.5 (3)
C1—N2—N3	128.0 (3)	N2—C1—H1	121.4
C1—N2—C4	121.9 (4)	C2—C1—N2	117.2 (4)
C3—N1—C4	115.2 (3)	C2—C1—H1	121.4
C5—N3—N2	101.0 (3)	N1—C4—N2	121.9 (4)
C4—N4—C5	102.2 (4)	N4—C4—N2	109.3 (4)
C3—C2—H2	121.0	N4—C4—N1	128.8 (4)
C1—C2—H2	121.0	N3—C5—N4	117.5 (4)
C1—C2—C3	117.9 (4)	N3—C5—H5	121.3
N1—C3—Br1	115.8 (3)	N4—C5—H5	121.3
N1—C3—C2	125.8 (4)

N2—N3—C5—N4	−0.6 (6)	C1—C2—C3—Br1	176.9 (4)
N3—N2—C1—C2	−178.9 (4)	C1—C2—C3—N1	−3.3 (7)
N3—N2—C4—N1	179.2 (4)	C4—N2—N3—C5	1.0 (5)
N3—N2—C4—N4	−1.2 (5)	C4—N2—C1—C2	1.4 (6)
C3—N1—C4—N2	−1.3 (6)	C4—N1—C3—Br1	−176.6 (3)
C3—N1—C4—N4	179.1 (4)	C4—N1—C3—C2	3.5 (6)
C3—C2—C1—N2	0.6 (6)	C4—N4—C5—N3	−0.1 (6)
C1—N2—N3—C5	−178.7 (4)	C5—N4—C4—N2	0.7 (5)
C1—N2—C4—N1	−1.1 (6)	C5—N4—C4—N1	−179.6 (4)
C1—N2—C4—N4	178.6 (4)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···N1ⁱ	0.93	2.52	3.421 (6)	164
C5—H5···N3ⁱⁱ	0.93	2.61	3.321 (6)	133

Symmetry codes: (i) x−1/2, −y+1/2, z+1/2; (ii) −x−1, −y, −z+2.

Acknowledgements

The authors thank the DST–PURSE, Mangalore University, Mangaluru, for providing the single-crystal X-ray diffraction facility. KSR thanks the DST, Indo-Korea programme (grant No. INT/Korea/dated/13/09/2011) and KBH thanks the UGC for providing a UGC meritorious fellowship.

References

Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339–341. Web of Science CrossRef CAS IUCr Journals Google Scholar
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Rigaku. (1999). NUMABS. Rigaku Corporation, Tokyo, Japan. Google Scholar
Rigaku (2011). CrystalClear SM Expert. Rigaku Corporation, Tokyo, Japan. Google Scholar
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ISSN: 2414-3146

Volume 1| Part 12| December 2016| x161944

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organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

5-Bromo-1,2,4-triazolo[1,5-a]pyrimidine

Structure description

Synthesis and crystallization

Refinement

Structural data

Acknowledgements

References

organic compounds