1-(1H-1,2,3-Benzotriazol-1-yl)-2-(4-meth­oxy­phen­yl)ethanone

Asiri, A.M.; Abo-Dya, N.E.; Arshad, M.N.; Alamry, K.A.; Shafiq, M.

doi:10.1107/S1600536812043759

organic compounds

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ISSN: 2056-9890

Volume 68| Part 11| November 2012| Page o3221

doi:10.1107/S1600536812043759

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1-(1H-1,2,3-Benzotriazol-1-yl)-2-(4-methoxyphenyl)ethanone

Abdullah M. Asiri,^a,^b ^* Nader E. Abo-Dya,^c Muhammad Nadeem Arshad,^b Khalid A. Alamry ^a,^b and Muhammad Shafiq ^d ^*

^aChemistry Department, Faculty of Science, King Abdulaziz University PO Box 80203 , Jeddah 21589, Saudi Arabia, ^bCenter of Excellence for Advanced Materials Research (CEAMR), Faculty of Science, King Abdulaziz University PO Box 80203, Jeddah 21589, Saudi Arabia, ^cDepartment of Pharmaceutical Organic Chemistry, Faculty of Pharmacy, Zagazig University, Zagazig, 44519, Egypt, and ^dDepartment of Chemistry, Government College University, Faisalabad 38040, Pakistan
^*Correspondence e-mail: aasiri2@kau.edu.sa, hafizshafique@hotmail.com

(Received 14 October 2012; accepted 22 October 2012; online 27 October 2012)

In the title compound, C₁₅H₁₃N₃O₂, the dihedral angle between the benzotriazole ring system (r.m.s. deviation = 0.0124 Å) and the benzene ring is 76.21 (3)°. The methoxy C atom deviates from its benzene ring plane by 0.063 (2)Å. In the crystal, inversion dimers linked by pairs of C—H⋯O hydrogen bonds generate R₂²(12) loops.

Related literature

For chemical background, see: Katritzky et al. (1996a ,b , 2005 , 2010 ). For a related structure, see: Selvarathy Grace et al. (2012 ). For related literature, see: Zou et al. (2006 ).

Experimental

Crystal data

C₁₅H₁₃N₃O₂
M_r = 267.28
Monoclinic, P 2₁ /c
a = 5.4209 (1) Å
b = 24.4894 (5) Å
c = 10.0555 (2) Å
β = 98.552 (2)°
V = 1320.07 (4) Å³
Z = 4
Cu Kα radiation
μ = 0.75 mm⁻¹
T = 296 K
0.34 × 0.17 × 0.16 mm

Data collection

Agilent SuperNova (Dual, Cu at zero, Atlas CCD) diffractometer
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012 ) T_min = 0.784, T_max = 0.889
6122 measured reflections
2707 independent reflections
2340 reflections with I > 2σ(I)
R_int = 0.019

Refinement

R[F² > 2σ(F²)] = 0.039
wR(F²) = 0.109
S = 1.08
2707 reflections
182 parameters
H-atom parameters constrained
Δρ_max = 0.14 e Å⁻³
Δρ_min = −0.16 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C5—H5⋯O1ⁱ	0.93	2.40	3.1912 (16)	143
Symmetry code: (i) -x, -y+1, -z+1.

Data collection: CrysAlis PRO (Agilent, 2012); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009 ); software used to prepare material for publication: WinGX (Farrugia, 1999 ) and X-SEED (Barbour, 2001 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536812043759/hb6975sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536812043759/hb6975Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536812043759/hb6975Isup3.cml

checkCIF report

Comment top

N-Acylbenzotriazoles are mild, regioselective and regiospecific reagents for N-, O-, C-, and S-acylation (Katritzky et al., 2010), & (Katritzky et al., 1996a). The title compound was previously converted into of a 1,3-diarylacetone (Katritzky et al., 2005) and an aryl benzyl sulfoxide (Katritzky et al., 1996b).

The title coompound is related in structure with 1-benzyl-1H-benzotriazole (Selvarathy Grace et al., 2012). The benzotriazole ring is almost planer with r.m.s. deviation of fitted non-hydrogen atoms (C1—C6/N1/N2/N3) is 0.0124 Å. The oxygen atom of carbonyl group is displaced at 0.0724 (2) Å with respect to benzotriazole. The methoxy benzene ring (C9—C14) is orientedted at dihedral angle of 76.21 (3)° with respect to benzotriazole rings. The C—H···O type weak hydrogen bonding interaction results in dimers about inversion center and generate twelve membered ring motif R₂²(12) (Table. 1, Fig. 2).

Related literature top

For chemical background, see: Katritzky et al. (1996a,b, 2005, 2010). For a related structure, see: Selvarathy Grace et al. (2012) For related literature, see: Zou et al. (2006).

Experimental top

A solution of thionyl chloride (0.4 ml, 5.5 mmol) and benzotriazole (1.79 g., 15 mmol) in methylene chloride (30 ml) was stirred at 293 K for 30 minutes. 2-(4-methoxypheny)acetic acid (0.83 g., 5 mmol) was then added and the heterogeneous mixture was stirred for 2 hr. The solid was filtered and methylene chloride (50mL) was added to the filtrate. The organic layer was extracted with saturated Na₂CO₃ (3 × 15 ml), brine (2 × 5 ml) and dried over anhyd. Na₂SO₄. Evaporation of methylene chloride solution afforded colourless prisms (1.21 g., 90% yield).

Computing details top

Data collection: CrysAlis PRO (Agilent, 2012); cell refinement: CrysAlis PRO (Agilent, 2012); data reduction: CrysAlis PRO (Agilent, 2012); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: WinGX (Farrugia, 1999) and X-SEED (Barbour, 2001).

Figures top

	Fig. 1. The molecular structure of (I) with 50% displacement ellipsoids.
	Fig. 2. Unit cell packing diagram showing intermolecular hydrogen bonds, drawn using dashed lines. Hydrogen atoms not involved in bonding have been omitted for clarity.

1-(1H-1,2,3-Benzotriazol-1-yl)-2-(4-methoxyphenyl)ethanone top

Crystal data top

C₁₅H₁₃N₃O₂	F(000) = 560
M_r = 267.28	D_x = 1.345 Mg m⁻³
Monoclinic, P2₁/c	Cu Kα radiation, λ = 1.54184 Å
Hall symbol: -P 2ybc	Cell parameters from 3661 reflections
a = 5.4209 (1) Å	θ = 4.4–76.0°
b = 24.4894 (5) Å	µ = 0.75 mm⁻¹
c = 10.0555 (2) Å	T = 296 K
β = 98.552 (2)°	Prismatic, colorless
V = 1320.07 (4) Å³	0.34 × 0.17 × 0.16 mm
Z = 4

Data collection top

Agilent SuperNova (Dual, Cu at zero, Atlas CCD) diffractometer	2707 independent reflections
Radiation source: SuperNova (Cu) X-ray Source	2340 reflections with I > 2σ(I)
Mirror monochromator	R_int = 0.019
ω scans	θ_max = 76.2°, θ_min = 4.8°
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012)	h = −6→4
T_min = 0.784, T_max = 0.889	k = −29→30
6122 measured reflections	l = −12→12

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) = 0.109	H-atom parameters constrained
S = 1.08	w = 1/[σ²(F_o²) + (0.0527P)² + 0.1534P] where P = (F_o² + 2F_c²)/3
2707 reflections	(Δ/σ)_max < 0.001
182 parameters	Δρ_max = 0.14 e Å⁻³
0 restraints	Δρ_min = −0.16 e Å⁻³

Crystal data top

C₁₅H₁₃N₃O₂	V = 1320.07 (4) Å³
M_r = 267.28	Z = 4
Monoclinic, P2₁/c	Cu Kα radiation
a = 5.4209 (1) Å	µ = 0.75 mm⁻¹
b = 24.4894 (5) Å	T = 296 K
c = 10.0555 (2) Å	0.34 × 0.17 × 0.16 mm
β = 98.552 (2)°

Data collection top

Agilent SuperNova (Dual, Cu at zero, Atlas CCD) diffractometer	2707 independent reflections
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012)	2340 reflections with I > 2σ(I)
T_min = 0.784, T_max = 0.889	R_int = 0.019
6122 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.039	0 restraints
wR(F²) = 0.109	H-atom parameters constrained
S = 1.08	Δρ_max = 0.14 e Å⁻³
2707 reflections	Δρ_min = −0.16 e Å⁻³
182 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
O1	0.2197 (2)	0.47488 (5)	0.37631 (10)	0.0750 (3)
O2	0.5718 (2)	0.24790 (4)	0.49538 (12)	0.0737 (3)
N1	0.17264 (19)	0.52715 (4)	0.19212 (9)	0.0463 (2)
N2	0.2345 (2)	0.54066 (5)	0.06808 (11)	0.0581 (3)
N3	0.1096 (2)	0.58305 (5)	0.02364 (12)	0.0640 (3)
C1	−0.0418 (2)	0.59893 (5)	0.11725 (13)	0.0517 (3)
C2	−0.2135 (3)	0.64152 (6)	0.11304 (15)	0.0647 (4)
H2	−0.2396	0.6657	0.0410	0.078*
C3	−0.3418 (3)	0.64602 (7)	0.21992 (16)	0.0680 (4)
H3	−0.4572	0.6741	0.2207	0.082*
C4	−0.3036 (3)	0.60952 (6)	0.32785 (15)	0.0639 (4)
H4	−0.3955	0.6139	0.3982	0.077*
C5	−0.1351 (3)	0.56739 (6)	0.33368 (13)	0.0538 (3)
H5	−0.1104	0.5431	0.4056	0.065*
C6	−0.0036 (2)	0.56326 (5)	0.22524 (11)	0.0445 (3)
C7	0.2792 (2)	0.48237 (5)	0.26753 (12)	0.0482 (3)
C8	0.4576 (2)	0.44711 (5)	0.20553 (13)	0.0522 (3)
H8A	0.6154	0.4661	0.2081	0.063*
H8B	0.3910	0.4401	0.1122	0.063*
C9	0.5001 (2)	0.39358 (5)	0.28009 (12)	0.0463 (3)
C10	0.7140 (2)	0.38340 (6)	0.36909 (14)	0.0553 (3)
H10	0.8398	0.4096	0.3802	0.066*
C11	0.7477 (2)	0.33526 (6)	0.44275 (14)	0.0559 (3)
H11	0.8941	0.3294	0.5020	0.067*
C12	0.5628 (2)	0.29645 (5)	0.42717 (13)	0.0501 (3)
C13	0.3460 (2)	0.30573 (6)	0.33780 (14)	0.0548 (3)
H13	0.2207	0.2795	0.3265	0.066*
C14	0.3161 (2)	0.35371 (5)	0.26571 (13)	0.0515 (3)
H14	0.1698	0.3595	0.2063	0.062*
C15	0.7849 (3)	0.23650 (8)	0.59061 (19)	0.0839 (5)
H15A	0.9308	0.2370	0.5469	0.126*
H15B	0.7676	0.2011	0.6293	0.126*
H15C	0.8010	0.2637	0.6602	0.126*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.1114 (9)	0.0677 (7)	0.0547 (6)	0.0257 (6)	0.0415 (6)	0.0192 (5)
O2	0.0810 (7)	0.0529 (6)	0.0814 (7)	−0.0002 (5)	−0.0071 (6)	0.0172 (5)
N1	0.0552 (5)	0.0463 (5)	0.0402 (5)	−0.0011 (4)	0.0166 (4)	0.0041 (4)
N2	0.0705 (7)	0.0606 (7)	0.0485 (6)	0.0056 (5)	0.0264 (5)	0.0127 (5)
N3	0.0781 (8)	0.0648 (7)	0.0534 (6)	0.0118 (6)	0.0244 (6)	0.0174 (5)
C1	0.0591 (7)	0.0498 (7)	0.0473 (6)	−0.0008 (5)	0.0118 (5)	0.0039 (5)
C2	0.0755 (9)	0.0577 (8)	0.0610 (8)	0.0103 (7)	0.0102 (7)	0.0080 (7)
C3	0.0720 (9)	0.0591 (9)	0.0735 (10)	0.0127 (7)	0.0128 (7)	−0.0067 (7)
C4	0.0719 (9)	0.0647 (9)	0.0591 (8)	0.0034 (7)	0.0230 (7)	−0.0109 (7)
C5	0.0671 (8)	0.0536 (7)	0.0432 (6)	−0.0022 (6)	0.0168 (6)	−0.0032 (5)
C6	0.0509 (6)	0.0425 (6)	0.0409 (6)	−0.0059 (5)	0.0092 (5)	−0.0029 (5)
C7	0.0583 (7)	0.0450 (6)	0.0438 (6)	−0.0031 (5)	0.0160 (5)	0.0044 (5)
C8	0.0561 (7)	0.0517 (7)	0.0525 (7)	−0.0008 (5)	0.0203 (5)	0.0058 (5)
C9	0.0460 (6)	0.0478 (6)	0.0475 (6)	0.0016 (5)	0.0149 (5)	0.0007 (5)
C10	0.0427 (6)	0.0570 (8)	0.0664 (8)	−0.0075 (5)	0.0089 (5)	0.0013 (6)
C11	0.0431 (6)	0.0616 (8)	0.0608 (8)	0.0038 (5)	0.0007 (5)	0.0016 (6)
C12	0.0540 (6)	0.0449 (6)	0.0513 (7)	0.0041 (5)	0.0075 (5)	−0.0001 (5)
C13	0.0527 (7)	0.0493 (7)	0.0603 (7)	−0.0088 (5)	0.0008 (6)	0.0007 (6)
C14	0.0473 (6)	0.0539 (7)	0.0514 (6)	−0.0020 (5)	0.0011 (5)	0.0014 (5)
C15	0.0787 (10)	0.0842 (12)	0.0863 (11)	0.0217 (9)	0.0046 (9)	0.0308 (10)

Geometric parameters (Å, º) top

O1—C7	1.1997 (14)	C7—C8	1.4997 (18)
O2—C12	1.3700 (16)	C8—C9	1.5106 (17)
O2—C15	1.414 (2)	C8—H8A	0.9700
N1—C6	1.3785 (16)	C8—H8B	0.9700
N1—N2	1.3792 (13)	C9—C10	1.3783 (18)
N1—C7	1.4075 (16)	C9—C14	1.3879 (17)
N2—N3	1.2829 (16)	C10—C11	1.3898 (19)
N3—C1	1.3928 (17)	C10—H10	0.9300
C1—C6	1.3849 (17)	C11—C12	1.3732 (18)
C1—C2	1.394 (2)	C11—H11	0.9300
C2—C3	1.368 (2)	C12—C13	1.3878 (18)
C2—H2	0.9300	C13—C14	1.3775 (18)
C3—C4	1.398 (2)	C13—H13	0.9300
C3—H3	0.9300	C14—H14	0.9300
C4—C5	1.373 (2)	C15—H15A	0.9600
C4—H4	0.9300	C15—H15B	0.9600
C5—C6	1.3924 (17)	C15—H15C	0.9600
C5—H5	0.9300

C12—O2—C15	118.34 (13)	C9—C8—H8A	109.5
C6—N1—N2	109.58 (10)	C7—C8—H8B	109.5
C6—N1—C7	127.83 (10)	C9—C8—H8B	109.5
N2—N1—C7	122.59 (10)	H8A—C8—H8B	108.1
N3—N2—N1	108.80 (10)	C10—C9—C14	117.56 (12)
N2—N3—C1	108.91 (10)	C10—C9—C8	122.04 (11)
C6—C1—N3	108.63 (11)	C14—C9—C8	120.32 (11)
C6—C1—C2	121.12 (12)	C9—C10—C11	122.05 (12)
N3—C1—C2	130.24 (12)	C9—C10—H10	119.0
C3—C2—C1	116.83 (13)	C11—C10—H10	119.0
C3—C2—H2	121.6	C12—C11—C10	119.37 (12)
C1—C2—H2	121.6	C12—C11—H11	120.3
C2—C3—C4	121.63 (14)	C10—C11—H11	120.3
C2—C3—H3	119.2	O2—C12—C11	124.94 (12)
C4—C3—H3	119.2	O2—C12—C13	115.46 (12)
C5—C4—C3	122.31 (13)	C11—C12—C13	119.60 (12)
C5—C4—H4	118.8	C14—C13—C12	120.17 (12)
C3—C4—H4	118.8	C14—C13—H13	119.9
C4—C5—C6	115.84 (13)	C12—C13—H13	119.9
C4—C5—H5	122.1	C13—C14—C9	121.25 (12)
C6—C5—H5	122.1	C13—C14—H14	119.4
N1—C6—C1	104.08 (10)	C9—C14—H14	119.4
N1—C6—C5	133.61 (12)	O2—C15—H15A	109.5
C1—C6—C5	122.28 (12)	O2—C15—H15B	109.5
O1—C7—N1	117.76 (11)	H15A—C15—H15B	109.5
O1—C7—C8	124.65 (12)	O2—C15—H15C	109.5
N1—C7—C8	117.59 (10)	H15A—C15—H15C	109.5
C7—C8—C9	110.69 (10)	H15B—C15—H15C	109.5
C7—C8—H8A	109.5

C6—N1—N2—N3	0.65 (15)	C6—N1—C7—O1	−2.9 (2)
C7—N1—N2—N3	−179.84 (12)	N2—N1—C7—O1	177.64 (13)
N1—N2—N3—C1	−0.39 (16)	C6—N1—C7—C8	176.55 (11)
N2—N3—C1—C6	0.00 (16)	N2—N1—C7—C8	−2.87 (17)
N2—N3—C1—C2	−178.46 (15)	O1—C7—C8—C9	14.73 (19)
C6—C1—C2—C3	−0.3 (2)	N1—C7—C8—C9	−164.72 (11)
N3—C1—C2—C3	178.03 (15)	C7—C8—C9—C10	−103.08 (14)
C1—C2—C3—C4	−0.3 (2)	C7—C8—C9—C14	73.62 (15)
C2—C3—C4—C5	0.4 (3)	C14—C9—C10—C11	−0.1 (2)
C3—C4—C5—C6	0.1 (2)	C8—C9—C10—C11	176.70 (12)
N2—N1—C6—C1	−0.62 (13)	C9—C10—C11—C12	−0.1 (2)
C7—N1—C6—C1	179.91 (12)	C15—O2—C12—C11	0.8 (2)
N2—N1—C6—C5	177.24 (13)	C15—O2—C12—C13	−178.41 (14)
C7—N1—C6—C5	−2.2 (2)	C10—C11—C12—O2	−178.87 (13)
N3—C1—C6—N1	0.38 (14)	C10—C11—C12—C13	0.3 (2)
C2—C1—C6—N1	179.01 (13)	O2—C12—C13—C14	178.92 (12)
N3—C1—C6—C5	−177.78 (12)	C11—C12—C13—C14	−0.3 (2)
C2—C1—C6—C5	0.8 (2)	C12—C13—C14—C9	0.1 (2)
C4—C5—C6—N1	−178.29 (13)	C10—C9—C14—C13	0.06 (19)
C4—C5—C6—C1	−0.75 (19)	C8—C9—C14—C13	−176.78 (12)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···O1ⁱ	0.93	2.40	3.1912 (16)	143

Symmetry code: (i) −x, −y+1, −z+1.

Experimental details

Crystal data
Chemical formula	C₁₅H₁₃N₃O₂
M_r	267.28
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	296
a, b, c (Å)	5.4209 (1), 24.4894 (5), 10.0555 (2)
β (°)	98.552 (2)
V (Å³)	1320.07 (4)
Z	4
Radiation type	Cu Kα
µ (mm⁻¹)	0.75
Crystal size (mm)	0.34 × 0.17 × 0.16

Data collection
Diffractometer	Agilent SuperNova (Dual, Cu at zero, Atlas CCD) diffractometer
Absorption correction	Multi-scan (CrysAlis PRO; Agilent, 2012)
T_min, T_max	0.784, 0.889
No. of measured, independent and observed [I > 2σ(I)] reflections	6122, 2707, 2340
R_int	0.019
(sin θ/λ)_max (Å⁻¹)	0.630

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.039, 0.109, 1.08
No. of reflections	2707
No. of parameters	182
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.14, −0.16

Computer programs: CrysAlis PRO (Agilent, 2012), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009), WinGX (Farrugia, 1999) and X-SEED (Barbour, 2001).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···O1ⁱ	0.93	2.40	3.1912 (16)	143

Symmetry code: (i) −x, −y+1, −z+1.

Acknowledgements

The authors thank the Deanship of Scientific Research at King Abdulaziz University for support of this research via Research Group Track of grant No. (3-102/428).

References

Agilent (2012). CrysAlis PRO. Agilent Technologies, Yarnton, England. Google Scholar
Barbour, L. J. (2001). J. Supramol. Chem. 1, 189–191. CrossRef CAS Google Scholar
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838. CrossRef CAS IUCr Journals Google Scholar
Katritzky, A. R., Abo-Dya, N. E., Tala, S. R., Ghazvini-Zadeh, E. H., Bajaj, K. & El-Feky, S. A. (2010). Synlett, pp. 1337–1340. Web of Science CrossRef Google Scholar
Katritzky, A. R., Soleiman, M. & Yang, B. (1996a). Heteroat. Chem. 7, 365–367. CrossRef CAS Web of Science Google Scholar
Katritzky, A. R., Suzuki, K. & Wang, Z. (2005). Synlett, pp. 1656–1665. Web of Science CrossRef Google Scholar
Katritzky, A. R., Yang, B. & Qian, Y. (1996b). Synlett, pp. 701–702. CrossRef Google Scholar
Selvarathy Grace, P., Jebas, S. R., Ravindran Durai Nayagam, B. & Schollmeyer, D. (2012). Acta Cryst. E68, o1132. CSD CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Zou, X., Wang, X., Cheng, C., Kong, L. & Mao, H. (2006). Tetrahedron Lett. 47, 3767–3771. Web of Science CrossRef CAS Google Scholar