Methyl 3,5-bis­[(3-chloro­pyrazin-2-yl)­oxy]benzoate

Srinivasan, T.; Kalpana, V.; Rajakumar, P.; Velmurugan, D.

doi:10.1107/S1600536813010465

organic compounds

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ISSN: 2056-9890

Volume 69| Part 5| May 2013| Page o777

https://doi.org/10.1107/S1600536813010465

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Methyl 3,5-bis[(3-chloropyrazin-2-yl)oxy]benzoate

Thothadri Srinivasan,^a Venkatesan Kalpana,^b Perumal Rajakumar ^b and Devadasan Velmurugan ^a ^*

^aCentre of Advanced Study in Crystallography and Biophysics, University of Madras, Guindy Campus, Chennai 600 025, India, and ^bDepartment of Organic Chemistry, University of Madras, Guindy Campus, Chennai 600 025, India
^*Correspondence e-mail: shirai2011@gmail.com

(Received 16 March 2013; accepted 17 April 2013; online 20 April 2013)

In the title compound, C₁₆H₁₀Cl₂N₄O₄, the pyrazine rings make dihedral angles of 67.82 (9) and 75.91 (9)° with the benzene ring, while the dihedral angle between the pyrazine rings is 44.69 (10)°. The methoxycarbonyl group makes a dihedral angle of 16.82 (8)° with the benzene ring to which it is attached. In the crystal, C—H⋯O hydrogen bonds link the molecules, forming chains running along the ab plane.

Related literature

For applications of the pyrazine ring system in drug development, see: Du et al. (2009 ); Dubinina et al. (2006 ); Ellsworth et al. (2007 ); Mukaiyama et al. (2007 ). For a related structure, see: Nasir et al. (2010 ).

Experimental

Crystal data

C₁₆H₁₀Cl₂N₄O₄
M_r = 393.18
Triclinic, $[P \overline 1]$
a = 8.5437 (15) Å
b = 9.2984 (18) Å
c = 11.545 (2) Å
α = 88.592 (10)°
β = 74.974 (9)°
γ = 73.231 (9)°
V = 846.9 (3) Å³
Z = 2
Mo Kα radiation
μ = 0.41 mm⁻¹
T = 293 K
0.30 × 0.25 × 0.20 mm

Data collection

Bruker SMART APEXII area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ) T_min = 0.886, T_max = 0.922
12425 measured reflections
3453 independent reflections
3076 reflections with I > 2σ(I)
R_int = 0.024

Refinement

R[F² > 2σ(F²)] = 0.039
wR(F²) = 0.124
S = 1.04
3453 reflections
236 parameters
H-atom parameters constrained
Δρ_max = 0.30 e Å⁻³
Δρ_min = −0.46 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C4—H4⋯O2ⁱ	0.93	2.47	3.192 (3)	135
Symmetry code: (i) x, y-1, z.

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012 ); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536813010465/pv2625sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536813010465/pv2625Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S1600536813010465/pv2625Isup3.cml

checkCIF report

Comment top

The pyrazine ring is a useful structural unit in medicinal chemistry and has found broad applications in drug development and can be used as antiproliferative agent (Dubinina et al., 2006), potent CXCR3 antagonist (Du et al., 2009), CB1 antagonist (Ellsworth et al., 2007) and c-Src inhibitor (Mukaiyama et al., 2007). In view of different applications of this class of compounds, we have undertaken the single-crystal structure determination of the title compound.

The bond distances and angles in the title compound (Fig. 1) agree very well with the corresponding bond distances and angles reported in a closely related compound (Nasir et al., 2010). In the title compound, the pyrazine ring (N1/N2/C1-C4) makes a dihedral angle of 67.82 (9)° with the benzene ring (C5-C10). The other pyrazine ring (N3/N4/C11-C14) makes a dihedral angle of 75.91 (9)° with the bezene ring. The dihedral angle between the two pyrazine rings is 44.69 (10)°. Moreover, the acteyl group (C15/03/04/C16) attached with the benzene ring makes a dihedral angle of 16.82 (8)° with the aryl ring. The chlorine atoms Cl1 and Cl2 attached with the pyrazine rings deviate by 0.0136 (6)Å and 0.0590 (7)Å. The crystal packing is stabilised by intermolecular C4–H4···O2 hydrogen bonds (Tab. 1 & Fig. 2).

Related literature top

For applications of the pyrazine ring system in drug development, see: Du et al. (2009); Dubinina et al. (2006); Ellsworth et al. (2007); Mukaiyama et al. (2007). For a related structure, see: Nasir et al. (2010).

Experimental top

To a stirred solution of Cs₂CO₃/K₂CO₃ (22 mmol) in CH₃CN (50 mL), methyl-3,5-dihydroxybenzoate (10 mmol) was added and stirred for 5 min. 2,3-Dichloropyrazine (20 mmol) in CH₃CN (100 mL) was added dropwise to the above reaction mixture and allowed for stirring at refluxing condition for 12 h. After the reaction was complete, the reaction mixture was allowed to attain room temperature and then evaporated to dryness. The residue obtained was extracted with CH₂Cl₂ (3 x 100 mL), washed with water (3 x 100 mL), brine and then dried over Na₂SO₄. Evaporation of the organic layer gave a residue, which on purification using column chromatography with hexane/CHCl₃ (1:1) as an eluent gave the title compound. Single crystals suitable for X-ray diffraction were obtained by slow evaporation of a solution of the title compound in hexane at room temperature.

Structure description top

For applications of the pyrazine ring system in drug development, see: Du et al. (2009); Dubinina et al. (2006); Ellsworth et al. (2007); Mukaiyama et al. (2007). For a related structure, see: Nasir et al. (2010).

Computing details top

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top

	Fig. 1. The molecular structure of the title compound, showing displacement ellipsoids drawn at the 30% probability level. H atoms are presented as small spheres of arbitrary radius.
	Fig. 2. The crystal packing of the title compound viewed down a axis. H-atoms not involved in H-bonds have been excluded for clarity.

Methyl 3,5-bis[(3-chloropyrazin-2-yl)oxy]benzoate top

Crystal data top

C₁₆H₁₀Cl₂N₄O₄	Z = 2
M_r = 393.18	F(000) = 400
Triclinic, P1	D_x = 1.542 Mg m⁻³
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 8.5437 (15) Å	Cell parameters from 3453 reflections
b = 9.2984 (18) Å	θ = 1.8–26.6°
c = 11.545 (2) Å	µ = 0.41 mm⁻¹
α = 88.592 (10)°	T = 293 K
β = 74.974 (9)°	Block, colourless
γ = 73.231 (9)°	0.30 × 0.25 × 0.20 mm
V = 846.9 (3) Å³

Data collection top

Bruker SMART APEXII area-detector diffractometer	3453 independent reflections
Radiation source: fine-focus sealed tube	3076 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.024
ω and φ scans	θ_max = 26.6°, θ_min = 1.8°
Absorption correction: multi-scan (SADABS; Bruker, 2008)	h = −10→10
T_min = 0.886, T_max = 0.922	k = −11→11
12425 measured reflections	l = −14→14

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.039	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.124	H-atom parameters constrained
S = 1.04	w = 1/[σ²(F_o²) + (0.0678P)² + 0.3652P] where P = (F_o² + 2F_c²)/3
3453 reflections	(Δ/σ)_max < 0.001
236 parameters	Δρ_max = 0.30 e Å⁻³
0 restraints	Δρ_min = −0.46 e Å⁻³

Crystal data top

C₁₆H₁₀Cl₂N₄O₄	γ = 73.231 (9)°
M_r = 393.18	V = 846.9 (3) Å³
Triclinic, P1	Z = 2
a = 8.5437 (15) Å	Mo Kα radiation
b = 9.2984 (18) Å	µ = 0.41 mm⁻¹
c = 11.545 (2) Å	T = 293 K
α = 88.592 (10)°	0.30 × 0.25 × 0.20 mm
β = 74.974 (9)°

Data collection top

Bruker SMART APEXII area-detector diffractometer	3453 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2008)	3076 reflections with I > 2σ(I)
T_min = 0.886, T_max = 0.922	R_int = 0.024
12425 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.039	0 restraints
wR(F²) = 0.124	H-atom parameters constrained
S = 1.04	Δρ_max = 0.30 e Å⁻³
3453 reflections	Δρ_min = −0.46 e Å⁻³
236 parameters

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.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > 2sigma(F²) is used only for calculating R-factors(gt) 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

	x	y	z	U_iso*/U_eq
C1	1.2164 (2)	−0.13661 (19)	0.56898 (15)	0.0357 (4)
C2	1.3326 (2)	−0.2435 (2)	0.48010 (16)	0.0392 (4)
C3	1.2200 (3)	−0.4217 (2)	0.5674 (2)	0.0512 (5)
H3	1.2182	−0.5212	0.5714	0.061*
C4	1.1050 (3)	−0.3171 (2)	0.65286 (19)	0.0486 (4)
H4	1.0265	−0.3476	0.7125	0.058*
C5	1.1396 (2)	0.10665 (18)	0.66279 (15)	0.0364 (4)
C6	1.1808 (2)	0.07829 (19)	0.77108 (16)	0.0377 (4)
H6	1.2538	−0.0136	0.7823	0.045*
C7	1.1100 (2)	0.19087 (19)	0.86279 (16)	0.0376 (4)
C8	0.9977 (2)	0.32842 (19)	0.84678 (16)	0.0394 (4)
H8	0.9532	0.4046	0.9073	0.047*
C9	0.9551 (2)	0.34790 (19)	0.73925 (17)	0.0376 (4)
C10	1.0255 (2)	0.23987 (19)	0.64574 (16)	0.0383 (4)
H10	0.9970	0.2562	0.5731	0.046*
C11	0.6780 (2)	0.5146 (2)	0.76707 (15)	0.0376 (4)
C12	0.5715 (2)	0.6516 (2)	0.74204 (17)	0.0443 (4)
C13	0.3460 (3)	0.5899 (3)	0.8520 (2)	0.0683 (7)
H13	0.2294	0.6121	0.8838	0.082*
C14	0.4482 (3)	0.4569 (3)	0.8760 (2)	0.0594 (6)
H14	0.3993	0.3908	0.9235	0.071*
C15	1.1546 (2)	0.1705 (2)	0.98024 (17)	0.0458 (4)
C16	1.2714 (4)	−0.0079 (3)	1.1083 (2)	0.0749 (8)
H16A	1.3582	0.0366	1.1128	0.112*
H16B	1.3125	−0.1150	1.1123	0.112*
H16C	1.1733	0.0318	1.1742	0.112*
N1	1.3349 (2)	−0.38465 (18)	0.47831 (15)	0.0479 (4)
N2	1.10203 (19)	−0.17218 (18)	0.65331 (14)	0.0427 (3)
N3	0.4081 (2)	0.6891 (2)	0.78443 (18)	0.0618 (5)
N4	0.6181 (2)	0.41812 (19)	0.83301 (15)	0.0462 (4)
O1	1.22265 (18)	0.00741 (14)	0.56204 (11)	0.0460 (3)
O2	0.84699 (15)	0.48570 (14)	0.71782 (13)	0.0445 (3)
O3	1.1276 (3)	0.27208 (19)	1.05207 (15)	0.0702 (5)
O4	1.2263 (2)	0.02685 (17)	0.99597 (13)	0.0623 (4)
Cl1	1.47807 (7)	−0.18931 (7)	0.36871 (5)	0.06146 (19)
Cl2	0.65455 (7)	0.77453 (6)	0.65015 (6)	0.06183 (19)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0370 (8)	0.0322 (8)	0.0376 (8)	−0.0068 (6)	−0.0133 (7)	0.0005 (7)
C2	0.0381 (8)	0.0391 (9)	0.0390 (9)	−0.0076 (7)	−0.0117 (7)	−0.0023 (7)
C3	0.0665 (13)	0.0348 (10)	0.0563 (12)	−0.0176 (9)	−0.0197 (10)	0.0023 (8)
C4	0.0532 (11)	0.0477 (11)	0.0505 (11)	−0.0232 (9)	−0.0137 (9)	0.0039 (9)
C5	0.0381 (8)	0.0292 (8)	0.0387 (9)	−0.0092 (6)	−0.0052 (7)	−0.0010 (7)
C6	0.0351 (8)	0.0289 (8)	0.0434 (9)	−0.0028 (6)	−0.0078 (7)	0.0018 (7)
C7	0.0357 (8)	0.0336 (8)	0.0402 (9)	−0.0070 (7)	−0.0082 (7)	0.0030 (7)
C8	0.0371 (8)	0.0315 (8)	0.0433 (9)	−0.0049 (7)	−0.0050 (7)	−0.0018 (7)
C9	0.0310 (8)	0.0283 (8)	0.0498 (10)	−0.0052 (6)	−0.0087 (7)	0.0068 (7)
C10	0.0391 (9)	0.0361 (9)	0.0410 (9)	−0.0112 (7)	−0.0128 (7)	0.0059 (7)
C11	0.0367 (8)	0.0358 (9)	0.0377 (9)	−0.0049 (7)	−0.0113 (7)	−0.0021 (7)
C12	0.0453 (10)	0.0402 (10)	0.0426 (9)	−0.0009 (8)	−0.0161 (8)	0.0015 (8)
C13	0.0368 (10)	0.0936 (19)	0.0598 (13)	−0.0022 (11)	−0.0063 (9)	0.0058 (13)
C14	0.0465 (11)	0.0787 (16)	0.0515 (12)	−0.0204 (11)	−0.0089 (9)	0.0103 (11)
C15	0.0447 (10)	0.0449 (10)	0.0424 (10)	−0.0061 (8)	−0.0100 (8)	0.0018 (8)
C16	0.0865 (18)	0.0765 (17)	0.0503 (13)	0.0020 (14)	−0.0283 (12)	0.0137 (12)
N1	0.0530 (9)	0.0366 (8)	0.0518 (9)	−0.0062 (7)	−0.0168 (7)	−0.0036 (7)
N2	0.0406 (8)	0.0419 (8)	0.0449 (8)	−0.0126 (6)	−0.0093 (6)	−0.0002 (6)
N3	0.0438 (9)	0.0655 (12)	0.0591 (11)	0.0096 (8)	−0.0132 (8)	0.0027 (9)
N4	0.0418 (8)	0.0467 (9)	0.0483 (9)	−0.0107 (7)	−0.0114 (7)	0.0056 (7)
O1	0.0592 (8)	0.0332 (6)	0.0397 (7)	−0.0130 (6)	−0.0035 (6)	−0.0006 (5)
O2	0.0352 (6)	0.0316 (6)	0.0607 (8)	−0.0030 (5)	−0.0107 (6)	0.0111 (6)
O3	0.1037 (14)	0.0530 (9)	0.0501 (9)	−0.0085 (9)	−0.0293 (9)	−0.0063 (7)
O4	0.0801 (11)	0.0483 (8)	0.0498 (8)	0.0040 (7)	−0.0279 (8)	0.0045 (7)
Cl1	0.0616 (3)	0.0610 (3)	0.0520 (3)	−0.0218 (3)	0.0069 (2)	−0.0066 (2)
Cl2	0.0665 (3)	0.0411 (3)	0.0743 (4)	−0.0066 (2)	−0.0239 (3)	0.0175 (2)

Geometric parameters (Å, º) top

C1—N2	1.300 (2)	C9—C10	1.380 (3)
C1—O1	1.355 (2)	C9—O2	1.4057 (19)
C1—C2	1.407 (2)	C10—H10	0.9300
C2—N1	1.308 (2)	C11—N4	1.294 (2)
C2—Cl1	1.7185 (19)	C11—O2	1.356 (2)
C3—N1	1.340 (3)	C11—C12	1.409 (2)
C3—C4	1.370 (3)	C12—N3	1.297 (3)
C3—H3	0.9300	C12—Cl2	1.718 (2)
C4—N2	1.340 (3)	C13—N3	1.332 (3)
C4—H4	0.9300	C13—C14	1.362 (4)
C5—C6	1.384 (2)	C13—H13	0.9300
C5—C10	1.383 (2)	C14—N4	1.348 (3)
C5—O1	1.398 (2)	C14—H14	0.9300
C6—C7	1.393 (2)	C15—O3	1.203 (3)
C6—H6	0.9300	C15—O4	1.329 (2)
C7—C8	1.401 (2)	C16—O4	1.450 (3)
C7—C15	1.495 (3)	C16—H16A	0.9600
C8—C9	1.375 (3)	C16—H16B	0.9600
C8—H8	0.9300	C16—H16C	0.9600

N2—C1—O1	120.32 (16)	C5—C10—H10	120.8
N2—C1—C2	121.66 (16)	N4—C11—O2	120.75 (16)
O1—C1—C2	117.98 (15)	N4—C11—C12	121.81 (17)
N1—C2—C1	122.44 (17)	O2—C11—C12	117.44 (16)
N1—C2—Cl1	117.86 (14)	N3—C12—C11	122.06 (19)
C1—C2—Cl1	119.69 (14)	N3—C12—Cl2	117.28 (15)
N1—C3—C4	121.89 (18)	C11—C12—Cl2	120.64 (15)
N1—C3—H3	119.1	N3—C13—C14	121.9 (2)
C4—C3—H3	119.1	N3—C13—H13	119.0
N2—C4—C3	122.12 (18)	C14—C13—H13	119.0
N2—C4—H4	118.9	N4—C14—C13	122.0 (2)
C3—C4—H4	118.9	N4—C14—H14	119.0
C6—C5—C10	121.86 (16)	C13—C14—H14	119.0
C6—C5—O1	121.32 (15)	O3—C15—O4	124.21 (19)
C10—C5—O1	116.59 (15)	O3—C15—C7	123.90 (18)
C5—C6—C7	118.28 (15)	O4—C15—C7	111.88 (17)
C5—C6—H6	120.9	O4—C16—H16A	109.5
C7—C6—H6	120.9	O4—C16—H16B	109.5
C6—C7—C8	120.99 (16)	H16A—C16—H16B	109.5
C6—C7—C15	121.16 (15)	O4—C16—H16C	109.5
C8—C7—C15	117.83 (16)	H16A—C16—H16C	109.5
C9—C8—C7	118.26 (16)	H16B—C16—H16C	109.5
C9—C8—H8	120.9	C2—N1—C3	115.66 (17)
C7—C8—H8	120.9	C1—N2—C4	116.18 (17)
C8—C9—C10	122.16 (15)	C12—N3—C13	116.28 (19)
C8—C9—O2	120.22 (16)	C11—N4—C14	115.96 (18)
C10—C9—O2	117.42 (16)	C1—O1—C5	118.77 (13)
C9—C10—C5	118.35 (16)	C11—O2—C9	118.32 (13)
C9—C10—H10	120.8	C15—O4—C16	117.08 (18)

N2—C1—C2—N1	−1.4 (3)	C6—C7—C15—O4	−17.0 (3)
O1—C1—C2—N1	−179.07 (16)	C8—C7—C15—O4	164.56 (17)
N2—C1—C2—Cl1	178.52 (14)	C1—C2—N1—C3	−0.5 (3)
O1—C1—C2—Cl1	0.9 (2)	Cl1—C2—N1—C3	179.52 (14)
N1—C3—C4—N2	−0.9 (3)	C4—C3—N1—C2	1.6 (3)
C10—C5—C6—C7	−2.9 (3)	O1—C1—N2—C4	179.72 (16)
O1—C5—C6—C7	171.39 (15)	C2—C1—N2—C4	2.1 (3)
C5—C6—C7—C8	1.1 (3)	C3—C4—N2—C1	−1.0 (3)
C5—C6—C7—C15	−177.37 (16)	C11—C12—N3—C13	−0.8 (3)
C6—C7—C8—C9	1.9 (3)	Cl2—C12—N3—C13	177.75 (19)
C15—C7—C8—C9	−179.61 (16)	C14—C13—N3—C12	0.4 (4)
C7—C8—C9—C10	−3.3 (3)	O2—C11—N4—C14	−179.00 (18)
C7—C8—C9—O2	−178.05 (15)	C12—C11—N4—C14	0.0 (3)
C8—C9—C10—C5	1.5 (3)	C13—C14—N4—C11	−0.4 (3)
O2—C9—C10—C5	176.47 (15)	N2—C1—O1—C5	17.9 (2)
C6—C5—C10—C9	1.6 (3)	C2—C1—O1—C5	−164.46 (15)
O1—C5—C10—C9	−172.90 (15)	C6—C5—O1—C1	59.1 (2)
N4—C11—C12—N3	0.6 (3)	C10—C5—O1—C1	−126.30 (17)
O2—C11—C12—N3	179.63 (18)	N4—C11—O2—C9	0.6 (3)
N4—C11—C12—Cl2	−177.87 (15)	C12—C11—O2—C9	−178.44 (16)
O2—C11—C12—Cl2	1.2 (2)	C8—C9—O2—C11	−78.8 (2)
N3—C13—C14—N4	0.2 (4)	C10—C9—O2—C11	106.15 (18)
C6—C7—C15—O3	163.5 (2)	O3—C15—O4—C16	1.1 (3)
C8—C7—C15—O3	−15.0 (3)	C7—C15—O4—C16	−178.4 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···O2ⁱ	0.93	2.47	3.192 (3)	135

Symmetry code: (i) x, y−1, z.

Experimental details

Crystal data
Chemical formula	C₁₆H₁₀Cl₂N₄O₄
M_r	393.18
Crystal system, space group	Triclinic, P1
Temperature (K)	293
a, b, c (Å)	8.5437 (15), 9.2984 (18), 11.545 (2)
α, β, γ (°)	88.592 (10), 74.974 (9), 73.231 (9)
V (Å³)	846.9 (3)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.41
Crystal size (mm)	0.30 × 0.25 × 0.20

Data collection
Diffractometer	Bruker SMART APEXII area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2008)
T_min, T_max	0.886, 0.922
No. of measured, independent and observed [I > 2σ(I)] reflections	12425, 3453, 3076
R_int	0.024
(sin θ/λ)_max (Å⁻¹)	0.629

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.039, 0.124, 1.04
No. of reflections	3453
No. of parameters	236
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.30, −0.46

Computer programs: APEX2 (Bruker, 2008), SAINT (Bruker, 2008), SHELXS97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 2012), SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···O2ⁱ	0.93	2.47	3.192 (3)	135

Symmetry code: (i) x, y−1, z.

Acknowledgements

The authors thank the TBI X-ray facility, CAS in Crystallography and Biophysics, University of Madras, India, for the data collection. TS thanks the DST for an Inspire fellowship. The UGC (SAP–CAS) is acknowleged for departmental facilities.

References

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