6-Benzyl 4-ethyl 2-chloro-5,6,7,8-tetra­hydro­pyrido[4,3-d]pyrimidine-4,6-di­carboxyl­ate

Guo, H.-M.

doi:10.1107/S1600536811034313

organic compounds

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ISSN: 2056-9890

Volume 67| Part 9| September 2011| Page o2516

doi:10.1107/S1600536811034313

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6-Benzyl 4-ethyl 2-chloro-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine-4,6-dicarboxylate

Huan-Mei Guo ^a ^*

^aMicroscale Science Institute, Weifang University, Weifang 261061, People's Republic of China
^*Correspondence e-mail: huanmeiguo@163.com

(Received 5 August 2011; accepted 21 August 2011; online 27 August 2011)

In the title compound, C₁₈H₁₈ClN₃O₄, the dihedral angle between the pyrimidine ring and the N-bonded ester grouping is 56.27 (7)° and the dihedral angle between the aromatic rings is 11.23 (7)°.

Related literature

For background to the biological activities of pyrimidine compounds, see: Patil et al. (2003 ); Siddiqui et al. (2007 ).

Experimental

Crystal data

C₁₈H₁₈ClN₃O₄
M_r = 375.80
Monoclinic, P 2₁ /c
a = 11.530 (2) Å
b = 12.384 (2) Å
c = 14.010 (3) Å
β = 119.820 (4)°
V = 1735.6 (6) Å³
Z = 4
Mo Kα radiation
μ = 0.25 mm⁻¹
T = 173 K
0.23 × 0.20 × 0.16 mm

Data collection

MM007-HF CCD (Saturn 724+) diffractometer
Absorption correction: multi-scan (CrystalClear; Rigaku, 2007 ) T_min = 0.945, T_max = 0.961
8909 measured reflections
3925 independent reflections
3518 reflections with I > 2σ(I)
R_int = 0.038

Refinement

R[F² > 2σ(F²)] = 0.058
wR(F²) = 0.142
S = 1.09
3925 reflections
236 parameters
H-atom parameters constrained
Δρ_max = 0.65 e Å⁻³
Δρ_min = −0.70 e Å⁻³

Data collection: CrystalClear (Rigaku, 2007); cell refinement: CrystalClear; data reduction: CrystalClear; 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.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811034313/hb6350sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811034313/hb6350Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811034313/hb6350Isup3.cml

checkCIF report

Comment top

Pyrimidine is a widespread heterocyclic moiety present in numerous natural products. Pyrimidines are important not only because they are an integral part of genetic materials, but also they have important biodynamic properties and biological activities (e.g. Siddiqui et al. (2007); Patil et al. (2003).

In continuation of our interest in the synthesis of the biologically active heterocyclic compound, here we report the sigle crystal structure of the title compound, (I). In the molecule (Fig. 1), atoms N1,C1,N2,C2,C3 and C4 lie in a plane (p1), with a maximum deviation of 0.0312 (13) Å, atoms N3,C11,O3,O4, and C12 lie in a plane (p2) too, the maximum deviation is 0.0647 (13) Å. The dihedral angle between p1 and p2 is 56.27 (7)°. The dihedral angles made by the phenyl ring with p1 and p2 are 11.23 (7)° and 60.25 (8)°, respectively.

Related literature top

For background to the biological activities of pyrimidine compounds, see: Patil et al. (2003); Siddiqui et al. (2007).

Experimental top

5-tert-butyl 3-ethyl 1-isopropyl-6,7-dihydro-1H-pyrazolo[4,3-c] pyridine-3,5(4H)-dicarboxylate was synthesized with 6-benzyl 4-ethyl 2-hydroxy-7,8-dihydropyrido[4,3-d] pyrimidine-4,6(5H)- dicarboxylate (1 eq), andN,N-dimethylaniline (2 eq) in POCl3 (as solvent) in refluxing for 3 hrs. Colourless blocks of (I) were obtained by recrystallization from ethanol at room temperature.

Computing details top

Data collection: CrystalClear (Rigaku, 2007); cell refinement: CrystalClear (Rigaku, 2007); data reduction: CrystalClear (Rigaku, 2007); 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 (Sheldrick, 2008).

Figures top

Fig. 1. The molecular structure of (I) with displacement ellipsoids drawn at the 50% probability level.

6-Benzyl 4-ethyl 2-chloro-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine-4,6-dicarboxylate top

Crystal data top

C₁₈H₁₈ClN₃O₄	F(000) = 784
M_r = 375.80	D_x = 1.438 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 6088 reflections
a = 11.530 (2) Å	θ = 1.6–27.5°
b = 12.384 (2) Å	µ = 0.25 mm⁻¹
c = 14.010 (3) Å	T = 173 K
β = 119.820 (4)°	Block, colorless
V = 1735.6 (6) Å³	0.23 × 0.20 × 0.16 mm
Z = 4

Data collection top

MM007-HF CCD (Saturn 724+) diffractometer	3925 independent reflections
Radiation source: rotating anode	3518 reflections with I > 2σ(I)
Confocal monochromator	R_int = 0.038
ω scans at fixed χ = 45°	θ_max = 27.5°, θ_min = 2.0°
Absorption correction: multi-scan (CrystalClear; Rigaku, 2007)	h = −14→12
T_min = 0.945, T_max = 0.961	k = −12→16
8909 measured reflections	l = −16→18

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)] = 0.058	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.142	H-atom parameters constrained
S = 1.09	w = 1/[σ²(F_o²) + (0.0565P)² + 1.1725P] where P = (F_o² + 2F_c²)/3
3925 reflections	(Δ/σ)_max < 0.001
236 parameters	Δρ_max = 0.65 e Å⁻³
0 restraints	Δρ_min = −0.70 e Å⁻³

Crystal data top

C₁₈H₁₈ClN₃O₄	V = 1735.6 (6) Å³
M_r = 375.80	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 11.530 (2) Å	µ = 0.25 mm⁻¹
b = 12.384 (2) Å	T = 173 K
c = 14.010 (3) Å	0.23 × 0.20 × 0.16 mm
β = 119.820 (4)°

Data collection top

MM007-HF CCD (Saturn 724+) diffractometer	3925 independent reflections
Absorption correction: multi-scan (CrystalClear; Rigaku, 2007)	3518 reflections with I > 2σ(I)
T_min = 0.945, T_max = 0.961	R_int = 0.038
8909 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.058	0 restraints
wR(F²) = 0.142	H-atom parameters constrained
S = 1.09	Δρ_max = 0.65 e Å⁻³
3925 reflections	Δρ_min = −0.70 e Å⁻³
236 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 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 > σ(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
Cl1	0.70799 (5)	0.21924 (5)	0.19746 (6)	0.0470 (2)
O1	0.11289 (14)	0.13056 (12)	0.00647 (13)	0.0367 (4)
O2	0.29267 (15)	0.02745 (12)	0.10881 (13)	0.0405 (4)
O3	0.04486 (14)	0.60281 (12)	−0.14053 (12)	0.0329 (3)
O4	−0.02266 (14)	0.43250 (12)	−0.20318 (12)	0.0349 (4)
N1	0.51941 (17)	0.36384 (15)	0.13641 (14)	0.0320 (4)
N2	0.45847 (16)	0.17871 (14)	0.12649 (14)	0.0299 (4)
N3	0.12864 (17)	0.46466 (14)	−0.02346 (14)	0.0316 (4)
C1	0.5421 (2)	0.25868 (18)	0.14647 (17)	0.0315 (4)
C2	0.33018 (19)	0.20875 (16)	0.08209 (15)	0.0256 (4)
C3	0.28806 (18)	0.31618 (16)	0.05975 (14)	0.0246 (4)
C4	0.3906 (2)	0.39277 (17)	0.09374 (16)	0.0280 (4)
C5	0.14314 (19)	0.35043 (16)	0.00482 (16)	0.0282 (4)
H5A	0.0904	0.3072	−0.0627	0.034*
H5B	0.1076	0.3363	0.0550	0.034*
C6	0.2223 (2)	0.53565 (17)	0.06382 (17)	0.0353 (5)
H6A	0.2174	0.5234	0.1315	0.042*
H6B	0.1992	0.6120	0.0415	0.042*
C7	0.3628 (2)	0.51207 (17)	0.08584 (19)	0.0365 (5)
H7A	0.3741	0.5431	0.0258	0.044*
H7B	0.4284	0.5473	0.1555	0.044*
C8	0.2320 (2)	0.11846 (16)	0.06036 (16)	0.0280 (4)
C9	0.2049 (2)	−0.0631 (2)	0.0968 (2)	0.0466 (6)
H9A	0.1219	−0.0353	0.0924	0.056*
H9B	0.2500	−0.1104	0.1623	0.056*
C10	0.1705 (3)	−0.1273 (2)	−0.0041 (2)	0.0520 (7)
H10A	0.1185	−0.0824	−0.0694	0.078*
H10B	0.1175	−0.1905	−0.0072	0.078*
H10C	0.2528	−0.1511	−0.0019	0.078*
C11	0.04534 (18)	0.49442 (17)	−0.12869 (16)	0.0279 (4)
C12	−0.0290 (2)	0.6427 (2)	−0.25290 (18)	0.0364 (5)
H12A	−0.0266	0.5874	−0.3030	0.044*
H12B	0.0157	0.7083	−0.2592	0.044*
C13	−0.1726 (2)	0.66913 (17)	−0.28908 (16)	0.0293 (4)
C14	−0.2715 (2)	0.59019 (18)	−0.32842 (17)	0.0343 (5)
H14	−0.2482	0.5171	−0.3310	0.041*
C15	−0.4040 (2)	0.6170 (2)	−0.36400 (18)	0.0390 (5)
H15	−0.4707	0.5624	−0.3894	0.047*
C16	−0.4380 (2)	0.7237 (2)	−0.36211 (18)	0.0388 (5)
H16	−0.5285	0.7426	−0.3874	0.047*
C17	−0.3409 (2)	0.8033 (2)	−0.32367 (18)	0.0370 (5)
H17	−0.3647	0.8766	−0.3228	0.044*
C18	−0.2084 (2)	0.77566 (18)	−0.28631 (17)	0.0321 (4)
H18	−0.1416	0.8302	−0.2586	0.039*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.0225 (3)	0.0441 (3)	0.0666 (4)	−0.0014 (2)	0.0163 (3)	−0.0168 (3)
O1	0.0234 (7)	0.0309 (8)	0.0474 (9)	−0.0025 (6)	0.0112 (6)	0.0032 (7)
O2	0.0296 (8)	0.0273 (8)	0.0499 (9)	−0.0021 (6)	0.0085 (7)	0.0081 (7)
O3	0.0283 (7)	0.0276 (7)	0.0328 (7)	0.0048 (6)	0.0077 (6)	0.0067 (6)
O4	0.0286 (7)	0.0335 (8)	0.0307 (7)	0.0053 (6)	0.0057 (6)	−0.0014 (6)
N1	0.0244 (8)	0.0322 (9)	0.0354 (9)	−0.0054 (7)	0.0118 (7)	−0.0068 (7)
N2	0.0231 (8)	0.0311 (9)	0.0313 (8)	−0.0004 (7)	0.0103 (7)	−0.0049 (7)
N3	0.0283 (9)	0.0249 (9)	0.0290 (8)	0.0018 (7)	0.0047 (7)	0.0018 (7)
C1	0.0221 (9)	0.0352 (11)	0.0329 (10)	−0.0015 (8)	0.0105 (8)	−0.0072 (9)
C2	0.0228 (9)	0.0274 (10)	0.0226 (8)	−0.0002 (7)	0.0083 (7)	−0.0005 (7)
C3	0.0222 (9)	0.0273 (9)	0.0212 (8)	−0.0019 (7)	0.0083 (7)	−0.0002 (7)
C4	0.0266 (9)	0.0289 (10)	0.0249 (9)	−0.0033 (8)	0.0100 (8)	−0.0025 (8)
C5	0.0223 (9)	0.0274 (10)	0.0291 (10)	0.0014 (8)	0.0083 (8)	0.0033 (8)
C6	0.0347 (11)	0.0264 (10)	0.0312 (10)	0.0027 (8)	0.0061 (9)	−0.0025 (8)
C7	0.0314 (11)	0.0259 (10)	0.0397 (12)	−0.0054 (9)	0.0084 (9)	−0.0023 (9)
C8	0.0268 (10)	0.0259 (10)	0.0278 (9)	−0.0012 (8)	0.0110 (8)	0.0004 (7)
C9	0.0371 (12)	0.0343 (12)	0.0531 (14)	−0.0074 (10)	0.0108 (11)	0.0146 (11)
C10	0.0436 (14)	0.0340 (13)	0.0746 (18)	−0.0014 (11)	0.0264 (13)	−0.0056 (12)
C11	0.0208 (9)	0.0292 (10)	0.0312 (10)	0.0027 (8)	0.0110 (8)	0.0012 (8)
C12	0.0275 (11)	0.0420 (13)	0.0359 (11)	0.0062 (9)	0.0130 (9)	0.0148 (9)
C13	0.0252 (9)	0.0332 (11)	0.0262 (9)	0.0037 (8)	0.0103 (8)	0.0092 (8)
C14	0.0298 (10)	0.0340 (11)	0.0331 (10)	0.0035 (9)	0.0110 (9)	0.0066 (9)
C15	0.0290 (11)	0.0460 (13)	0.0351 (11)	−0.0053 (10)	0.0107 (9)	0.0017 (10)
C16	0.0256 (10)	0.0527 (14)	0.0339 (11)	0.0078 (10)	0.0116 (9)	0.0047 (10)
C17	0.0362 (11)	0.0393 (12)	0.0343 (11)	0.0076 (10)	0.0167 (9)	0.0036 (9)
C18	0.0292 (10)	0.0344 (11)	0.0294 (10)	−0.0010 (9)	0.0120 (8)	0.0053 (8)

Geometric parameters (Å, º) top

Cl1—C1	1.746 (2)	C6—H6B	0.9900
O1—C8	1.203 (2)	C7—H7A	0.9900
O2—C8	1.322 (2)	C7—H7B	0.9900
O2—C9	1.463 (3)	C9—C10	1.493 (4)
O3—C11	1.352 (2)	C9—H9A	0.9900
O3—C12	1.454 (2)	C9—H9B	0.9900
O4—C11	1.216 (2)	C10—H10A	0.9800
N1—C1	1.322 (3)	C10—H10B	0.9800
N1—C4	1.344 (3)	C10—H10C	0.9800
N2—C1	1.312 (3)	C12—C13	1.508 (3)
N2—C2	1.341 (2)	C12—H12A	0.9900
N3—C11	1.350 (2)	C12—H12B	0.9900
N3—C5	1.456 (3)	C13—C18	1.389 (3)
N3—C6	1.456 (3)	C13—C14	1.391 (3)
C2—C3	1.397 (3)	C14—C15	1.392 (3)
C2—C8	1.510 (3)	C14—H14	0.9500
C3—C4	1.402 (3)	C15—C16	1.383 (3)
C3—C5	1.512 (3)	C15—H15	0.9500
C4—C7	1.504 (3)	C16—C17	1.383 (3)
C5—H5A	0.9900	C16—H16	0.9500
C5—H5B	0.9900	C17—C18	1.389 (3)
C6—C7	1.519 (3)	C17—H17	0.9500
C6—H6A	0.9900	C18—H18	0.9500

C8—O2—C9	115.82 (17)	O2—C9—C10	111.1 (2)
C11—O3—C12	115.75 (17)	O2—C9—H9A	109.4
C1—N1—C4	115.24 (17)	C10—C9—H9A	109.4
C1—N2—C2	114.46 (18)	O2—C9—H9B	109.4
C11—N3—C5	119.03 (17)	C10—C9—H9B	109.4
C11—N3—C6	125.44 (18)	H9A—C9—H9B	108.0
C5—N3—C6	114.90 (16)	C9—C10—H10A	109.5
N2—C1—N1	129.44 (19)	C9—C10—H10B	109.5
N2—C1—Cl1	114.57 (16)	H10A—C10—H10B	109.5
N1—C1—Cl1	115.97 (16)	C9—C10—H10C	109.5
N2—C2—C3	123.25 (18)	H10A—C10—H10C	109.5
N2—C2—C8	115.55 (17)	H10B—C10—H10C	109.5
C3—C2—C8	121.17 (17)	O4—C11—N3	124.76 (19)
C2—C3—C4	115.31 (18)	O4—C11—O3	124.00 (18)
C2—C3—C5	123.65 (17)	N3—C11—O3	111.23 (17)
C4—C3—C5	121.03 (18)	O3—C12—C13	113.06 (17)
N1—C4—C3	121.96 (19)	O3—C12—H12A	109.0
N1—C4—C7	116.26 (18)	C13—C12—H12A	109.0
C3—C4—C7	121.77 (18)	O3—C12—H12B	109.0
N3—C5—C3	111.06 (16)	C13—C12—H12B	109.0
N3—C5—H5A	109.4	H12A—C12—H12B	107.8
C3—C5—H5A	109.4	C18—C13—C14	118.86 (19)
N3—C5—H5B	109.4	C18—C13—C12	119.29 (19)
C3—C5—H5B	109.4	C14—C13—C12	121.8 (2)
H5A—C5—H5B	108.0	C13—C14—C15	120.8 (2)
N3—C6—C7	108.99 (18)	C13—C14—H14	119.6
N3—C6—H6A	109.9	C15—C14—H14	119.6
C7—C6—H6A	109.9	C16—C15—C14	119.5 (2)
N3—C6—H6B	109.9	C16—C15—H15	120.3
C7—C6—H6B	109.9	C14—C15—H15	120.3
H6A—C6—H6B	108.3	C15—C16—C17	120.4 (2)
C4—C7—C6	111.75 (18)	C15—C16—H16	119.8
C4—C7—H7A	109.3	C17—C16—H16	119.8
C6—C7—H7A	109.3	C16—C17—C18	119.8 (2)
C4—C7—H7B	109.3	C16—C17—H17	120.1
C6—C7—H7B	109.3	C18—C17—H17	120.1
H7A—C7—H7B	107.9	C13—C18—C17	120.7 (2)
O1—C8—O2	125.15 (19)	C13—C18—H18	119.7
O1—C8—C2	122.78 (18)	C17—C18—H18	119.7
O2—C8—C2	112.07 (16)

C2—N2—C1—N1	5.3 (3)	C9—O2—C8—O1	−1.8 (3)
C2—N2—C1—Cl1	−176.77 (14)	C9—O2—C8—C2	177.02 (18)
C4—N1—C1—N2	−4.1 (3)	N2—C2—C8—O1	−168.70 (19)
C4—N1—C1—Cl1	177.96 (14)	C3—C2—C8—O1	13.1 (3)
C1—N2—C2—C3	−0.7 (3)	N2—C2—C8—O2	12.5 (2)
C1—N2—C2—C8	−178.82 (17)	C3—C2—C8—O2	−165.70 (18)
N2—C2—C3—C4	−4.1 (3)	C8—O2—C9—C10	89.1 (3)
C8—C2—C3—C4	173.94 (17)	C5—N3—C11—O4	1.8 (3)
N2—C2—C3—C5	177.00 (18)	C6—N3—C11—O4	172.3 (2)
C8—C2—C3—C5	−5.0 (3)	C5—N3—C11—O3	−179.43 (17)
C1—N1—C4—C3	−1.7 (3)	C6—N3—C11—O3	−9.0 (3)
C1—N1—C4—C7	177.53 (19)	C12—O3—C11—O4	−8.4 (3)
C2—C3—C4—N1	5.3 (3)	C12—O3—C11—N3	172.86 (17)
C5—C3—C4—N1	−175.74 (18)	C11—O3—C12—C13	91.6 (2)
C2—C3—C4—C7	−173.87 (18)	O3—C12—C13—C18	98.8 (2)
C5—C3—C4—C7	5.1 (3)	O3—C12—C13—C14	−83.2 (3)
C11—N3—C5—C3	124.66 (19)	C18—C13—C14—C15	−0.3 (3)
C6—N3—C5—C3	−46.7 (2)	C12—C13—C14—C15	−178.33 (19)
C2—C3—C5—N3	−170.82 (17)	C13—C14—C15—C16	1.3 (3)
C4—C3—C5—N3	10.3 (3)	C14—C15—C16—C17	−1.0 (3)
C11—N3—C6—C7	−104.5 (2)	C15—C16—C17—C18	−0.3 (3)
C5—N3—C6—C7	66.2 (2)	C14—C13—C18—C17	−1.0 (3)
N1—C4—C7—C6	−165.93 (18)	C12—C13—C18—C17	177.13 (19)
C3—C4—C7—C6	13.3 (3)	C16—C17—C18—C13	1.2 (3)
N3—C6—C7—C4	−46.0 (2)

Experimental details

Crystal data
Chemical formula	C₁₈H₁₈ClN₃O₄
M_r	375.80
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	173
a, b, c (Å)	11.530 (2), 12.384 (2), 14.010 (3)
β (°)	119.820 (4)
V (Å³)	1735.6 (6)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.25
Crystal size (mm)	0.23 × 0.20 × 0.16

Data collection
Diffractometer	MM007-HF CCD (Saturn 724+) diffractometer
Absorption correction	Multi-scan (CrystalClear; Rigaku, 2007)
T_min, T_max	0.945, 0.961
No. of measured, independent and observed [I > 2σ(I)] reflections	8909, 3925, 3518
R_int	0.038
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.058, 0.142, 1.09
No. of reflections	3925
No. of parameters	236
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.65, −0.70

Computer programs: CrystalClear (Rigaku, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Acknowledgements

The author thanks Shandong Provincial Natural Science Foundation, China (Y2008B29) and Yuandu Scholar of Weifang City for support.

References

Patil, L. R., Mandhare, P. N., Bondge, S. P., Munde, S. B. & Mane, R. (2003). Indian J. Heterocycl. Chem. 12, 245–248. Google Scholar
Rigaku (2007). CrystalClear. Rigaku Corporation, Tokyo, Japan. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Siddiqui, A. A., Rajesh, R. Mojahid-Ul-Islam, Alagarsamy, V., Meyyanathan, S. N., Kumar, B. P. & Suresh, B. (2007). Acta Pol. Pharm. 64, 17–26. CAS Google Scholar

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