2-(4-Chloro­phen­yl)-2-oxoethyl 2-meth­oxy­benzoate

Fun, H.-K.; Asik, S.I.J.; Garudachari, B.; Isloor, A.M.; Satyanarayan, M.N.

doi:10.1107/S1600536811021246

organic compounds

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ISSN: 2056-9890

Volume 67| Part 7| July 2011| Page o1687

doi:10.1107/S1600536811021246

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2-(4-Chlorophenyl)-2-oxoethyl 2-methoxybenzoate

Hoong-Kun Fun,^a ^*‡ Safra Izuani Jama Asik,^a B. Garudachari,^b Arun M. Isloor ^b and M. N. Satyanarayan ^c

^aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, ^bOrganic Electronics Division, Department of Chemistry, National Institute of Technology–Karnataka, Surathkal, Mangalore 575 025, India, and ^cDepartment of Physics, National Institute of Technology–Karnataka, Surathkal, Mangalore 575 025, India
^*Correspondence e-mail: hkfun@usm.my

(Received 1 June 2011; accepted 2 June 2011; online 18 June 2011)

In the title compound, C₁₆H₁₃ClO₄, the two benzene rings make a dihedral angle of 86.38 (8)°. In the crystal, intermolecular C—H⋯O hydrogen bonds link the molecules to form columns along the a axis. The molecules are also stabilized by a π–π stacking interaction, with a centroid–centroid distance of 3.7793 (10) Å between the inversion-related benzene rings.

Related literature

For general background to phenacyl benzoates, see: Rather & Reid (1919 ); Sheehan & Umezaw (1973 ); Ruzicka et al. (2002 ); Litera et al. (2006 ). For applications and synthesis of oxazoles, imidazoles and benzoxazepines, see: Huang et al. (1996 ); Gandhi et al. (1995 ). For bond-length data, see: Allen et al. (1987 ).

Experimental

Crystal data

C₁₆H₁₃ClO₄
M_r = 304.71
Orthorhombic, P b c a
a = 7.7207 (6) Å
b = 14.4411 (12) Å
c = 26.064 (2) Å
V = 2906.0 (4) Å³
Z = 8
Mo Kα radiation
μ = 0.28 mm⁻¹
T = 296 K
0.51 × 0.29 × 0.19 mm

Data collection

Bruker APEXII DUO CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ) T_min = 0.829, T_max = 0.950
16215 measured reflections
4027 independent reflections
2731 reflections with I > 2σ(I)
R_int = 0.025

Refinement

R[F² > 2σ(F²)] = 0.041
wR(F²) = 0.116
S = 1.02
4027 reflections
190 parameters
H-atom parameters constrained
Δρ_max = 0.17 e Å⁻³
Δρ_min = −0.35 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2A⋯O1ⁱ	0.93	2.40	3.301 (2)	164
Symmetry code: (i) x+1, y, z.

Data collection: APEX2 (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 and PLATON (Spek, 2009 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811021246/is2727sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811021246/is2727Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811021246/is2727Isup3.cml

checkCIF report

Comment top

Phenacyl benzoate derivatives are very important in identification of organic acids (Rather & Reid, 1919) as they undergo photolysis in neutral and mild conditions (Sheehan & Umezaw, 1973; Ruzicka et al., 2002 ; Litera et al., 2006). They find applications in the field of synthetic chemistry for the synthesis of oxazoles, imidazoles (Huang et al., 1996) and benzoxazepines (Gandhi et al., 1995). The phenacyl esters are usually prepared by reaction between acids with phenacylbromide derivatives in DMF using sodium or potassium carbonate as base. We hereby report the crystal structure of 2-(4-chlorophenyl)-2-oxoethyl 2-methoxybenzoate, (I), which has potential commercial importance.

In the title compound of (I), the bond lengths (Allen et al., 1987) and angles show the normal values. The two benzene rings (C1–C6 and C10–C15) make a dihedral angle of 86.38 (8)°.

In the crystal packing (Fig. 2), intermolecular C2—H2A···O1 hydrogen bonds (Table 1) link the molecules to form columns down to the a-axis. The molecules are also stabilized by π–π stacking interactions between the inversion-related benzene rings (C1–C6 ; centroid Cg1) with a Cg1···Cg1ⁱⁱ separation of 3.7793 (10) Å [symmetry code: (ii) 2 - x, -y, 2 - z].

Related literature top

For general background to phenacyl benzoates, see: Rather & Reid (1919); Sheehan & Umezaw (1973) ; Ruzicka et al. (2002) ; Litera et al. (2006). For applications and synthesis of oxazoles, imidazoles and benzoxazepines, see: Huang et al. (1996); Gandhi et al. (1995). For bond-length data, see: Allen et al. (1987).

Experimental top

The mixture of 2-methoxybenzoic acid (1.0 g, 0.0065 mol), potassium carbonate (0.98 g, 0.0071 mol) and 2-bromo-1-(4-chlorophenyl)ethanone (1.45 g, 0.0065 mol) in dimethylformamide (10 ml) was stirred at room temperature for 2 h. On cooling, colorless needle-shaped crystals of 2-(4-chlorophenyl)-2-oxoethyl 2-methoxybenzoate begins to separate out. It was collected by filtration and recrystallized from ethanol. Yield : 1.9 g, 95 %, M.p. : 391–392 K, (CAS Registry Number: 282714–31–2).

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top

	Fig. 1. The structure of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme.
	Fig. 2. The crystal packing, viewed along the c axis, showing columns down to the a axis. Hydrogen atoms that are not involved in hydrogen bonding (dashed lines) are omitted for clarity.

2-(4-Chlorophenyl)-2-oxoethyl 2-methoxybenzoate top

Crystal data top

C₁₆H₁₃ClO₄	F(000) = 1264
M_r = 304.71	D_x = 1.393 Mg m⁻³
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 3855 reflections
a = 7.7207 (6) Å	θ = 2.9–29.2°
b = 14.4411 (12) Å	µ = 0.28 mm⁻¹
c = 26.064 (2) Å	T = 296 K
V = 2906.0 (4) Å³	Block, colourless
Z = 8	0.51 × 0.29 × 0.19 mm

Data collection top

Bruker APEXII DUO CCD area-detector diffractometer	4027 independent reflections
Radiation source: fine-focus sealed tube	2731 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.025
ϕ and ω scans	θ_max = 29.5°, θ_min = 2.9°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −10→9
T_min = 0.829, T_max = 0.950	k = −14→20
16215 measured reflections	l = −36→35

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)] = 0.041	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.116	H-atom parameters constrained
S = 1.02	w = 1/[σ²(F_o²) + (0.0471P)² + 0.6504P] where P = (F_o² + 2F_c²)/3
4027 reflections	(Δ/σ)_max = 0.001
190 parameters	Δρ_max = 0.17 e Å⁻³
0 restraints	Δρ_min = −0.35 e Å⁻³

Crystal data top

C₁₆H₁₃ClO₄	V = 2906.0 (4) Å³
M_r = 304.71	Z = 8
Orthorhombic, Pbca	Mo Kα radiation
a = 7.7207 (6) Å	µ = 0.28 mm⁻¹
b = 14.4411 (12) Å	T = 296 K
c = 26.064 (2) Å	0.51 × 0.29 × 0.19 mm

Data collection top

Bruker APEXII DUO CCD area-detector diffractometer	4027 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2009)	2731 reflections with I > 2σ(I)
T_min = 0.829, T_max = 0.950	R_int = 0.025
16215 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.041	0 restraints
wR(F²) = 0.116	H-atom parameters constrained
S = 1.02	Δρ_max = 0.17 e Å⁻³
4027 reflections	Δρ_min = −0.35 e Å⁻³
190 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
Cl1	1.18791 (7)	0.06652 (3)	1.10182 (2)	0.08142 (19)
O1	0.45975 (15)	0.12921 (11)	0.96747 (5)	0.0746 (4)
O2	0.49777 (16)	0.19520 (7)	0.87365 (5)	0.0624 (3)
O3	0.46624 (16)	0.04491 (8)	0.85569 (5)	0.0667 (3)
O4	0.19233 (15)	0.00492 (7)	0.79740 (4)	0.0600 (3)
C1	0.9263 (2)	0.14336 (11)	0.97782 (6)	0.0523 (4)
H1A	0.9515	0.1678	0.9457	0.063*
C2	1.0596 (2)	0.12582 (11)	1.01201 (7)	0.0571 (4)
H2A	1.1739	0.1382	1.0031	0.068*
C3	1.0198 (2)	0.08973 (10)	1.05937 (6)	0.0546 (4)
C4	0.8517 (2)	0.07047 (11)	1.07348 (7)	0.0582 (4)
H4A	0.8276	0.0459	1.1057	0.070*
C5	0.7198 (2)	0.08809 (11)	1.03928 (6)	0.0534 (4)
H5A	0.6059	0.0753	1.0485	0.064*
C6	0.75479 (19)	0.12480 (10)	0.99111 (6)	0.0455 (3)
C7	0.6086 (2)	0.14152 (10)	0.95508 (6)	0.0504 (4)
C8	0.6513 (2)	0.17422 (11)	0.90174 (6)	0.0543 (4)
H8A	0.7236	0.2290	0.9037	0.065*
H8B	0.7159	0.1265	0.8839	0.065*
C9	0.4084 (2)	0.12187 (10)	0.85521 (5)	0.0487 (3)
C10	0.2379 (2)	0.15154 (10)	0.83489 (5)	0.0462 (3)
C11	0.1787 (2)	0.24124 (11)	0.84420 (6)	0.0566 (4)
H11A	0.2469	0.2813	0.8635	0.068*
C12	0.0216 (3)	0.27210 (13)	0.82551 (7)	0.0672 (5)
H12A	−0.0156	0.3322	0.8321	0.081*
C13	−0.0790 (2)	0.21275 (13)	0.79706 (7)	0.0669 (5)
H13A	−0.1847	0.2331	0.7842	0.080*
C14	−0.0255 (2)	0.12352 (12)	0.78741 (6)	0.0594 (4)
H14A	−0.0954	0.0842	0.7682	0.071*
C15	0.1320 (2)	0.09184 (10)	0.80609 (5)	0.0475 (3)
C16	0.0868 (3)	−0.05690 (13)	0.76827 (8)	0.0822 (6)
H16A	0.1445	−0.1155	0.7650	0.123*
H16B	0.0669	−0.0313	0.7348	0.123*
H16C	−0.0221	−0.0655	0.7854	0.123*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.0864 (4)	0.0640 (3)	0.0939 (4)	0.0087 (2)	−0.0384 (3)	−0.0086 (2)
O1	0.0402 (6)	0.1070 (11)	0.0766 (8)	−0.0079 (7)	0.0051 (6)	−0.0064 (7)
O2	0.0648 (7)	0.0453 (6)	0.0772 (8)	−0.0033 (5)	−0.0195 (6)	−0.0001 (5)
O3	0.0694 (8)	0.0505 (6)	0.0802 (8)	0.0105 (6)	−0.0215 (6)	−0.0133 (5)
O4	0.0707 (8)	0.0479 (6)	0.0615 (6)	0.0005 (5)	−0.0169 (5)	−0.0098 (5)
C1	0.0459 (8)	0.0574 (8)	0.0537 (8)	−0.0062 (7)	0.0056 (7)	−0.0057 (7)
C2	0.0407 (8)	0.0584 (9)	0.0721 (10)	−0.0042 (7)	0.0000 (7)	−0.0136 (8)
C3	0.0601 (10)	0.0413 (7)	0.0623 (9)	0.0040 (7)	−0.0108 (8)	−0.0124 (6)
C4	0.0712 (11)	0.0506 (8)	0.0529 (9)	−0.0036 (8)	0.0003 (8)	−0.0043 (7)
C5	0.0501 (9)	0.0535 (8)	0.0566 (9)	−0.0060 (7)	0.0095 (7)	−0.0071 (7)
C6	0.0412 (7)	0.0440 (7)	0.0513 (8)	−0.0034 (6)	0.0038 (6)	−0.0112 (6)
C7	0.0443 (8)	0.0480 (7)	0.0590 (9)	−0.0049 (7)	0.0024 (7)	−0.0121 (6)
C8	0.0497 (9)	0.0506 (8)	0.0626 (9)	−0.0059 (7)	−0.0071 (7)	−0.0005 (7)
C9	0.0575 (9)	0.0461 (8)	0.0426 (7)	−0.0003 (7)	−0.0033 (6)	−0.0024 (6)
C10	0.0542 (8)	0.0453 (7)	0.0390 (7)	0.0017 (6)	−0.0006 (6)	0.0012 (6)
C11	0.0667 (10)	0.0495 (8)	0.0535 (8)	0.0043 (8)	−0.0017 (7)	−0.0030 (7)
C12	0.0761 (12)	0.0580 (10)	0.0674 (10)	0.0192 (9)	0.0019 (9)	0.0036 (8)
C13	0.0600 (10)	0.0755 (11)	0.0653 (10)	0.0117 (9)	−0.0070 (9)	0.0138 (9)
C14	0.0608 (10)	0.0640 (10)	0.0532 (9)	−0.0026 (8)	−0.0110 (7)	0.0066 (7)
C15	0.0560 (9)	0.0487 (7)	0.0377 (7)	0.0005 (7)	−0.0012 (6)	0.0033 (6)
C16	0.1015 (16)	0.0592 (10)	0.0859 (13)	−0.0046 (11)	−0.0344 (12)	−0.0164 (9)

Geometric parameters (Å, º) top

Cl1—C3	1.7380 (17)	C7—C8	1.505 (2)
O1—C7	1.2069 (19)	C8—H8A	0.9700
O2—C9	1.3521 (18)	C8—H8B	0.9700
O2—C8	1.426 (2)	C9—C10	1.482 (2)
O3—C9	1.1978 (18)	C10—C11	1.395 (2)
O4—C15	1.3579 (18)	C10—C15	1.406 (2)
O4—C16	1.428 (2)	C11—C12	1.381 (2)
C1—C2	1.384 (2)	C11—H11A	0.9300
C1—C6	1.395 (2)	C12—C13	1.374 (3)
C1—H1A	0.9300	C12—H12A	0.9300
C2—C3	1.375 (2)	C13—C14	1.376 (3)
C2—H2A	0.9300	C13—H13A	0.9300
C3—C4	1.377 (3)	C14—C15	1.388 (2)
C4—C5	1.377 (2)	C14—H14A	0.9300
C4—H4A	0.9300	C16—H16A	0.9600
C5—C6	1.390 (2)	C16—H16B	0.9600
C5—H5A	0.9300	C16—H16C	0.9600
C6—C7	1.488 (2)

C9—O2—C8	116.12 (12)	H8A—C8—H8B	108.0
C15—O4—C16	118.10 (13)	O3—C9—O2	122.20 (15)
C2—C1—C6	120.70 (15)	O3—C9—C10	127.08 (14)
C2—C1—H1A	119.6	O2—C9—C10	110.71 (12)
C6—C1—H1A	119.6	C11—C10—C15	118.16 (14)
C3—C2—C1	118.78 (15)	C11—C10—C9	119.82 (14)
C3—C2—H2A	120.6	C15—C10—C9	122.02 (13)
C1—C2—H2A	120.6	C12—C11—C10	121.74 (16)
C2—C3—C4	121.79 (15)	C12—C11—H11A	119.1
C2—C3—Cl1	118.55 (14)	C10—C11—H11A	119.1
C4—C3—Cl1	119.66 (14)	C13—C12—C11	119.05 (16)
C3—C4—C5	119.14 (16)	C13—C12—H12A	120.5
C3—C4—H4A	120.4	C11—C12—H12A	120.5
C5—C4—H4A	120.4	C12—C13—C14	120.86 (17)
C4—C5—C6	120.75 (15)	C12—C13—H13A	119.6
C4—C5—H5A	119.6	C14—C13—H13A	119.6
C6—C5—H5A	119.6	C13—C14—C15	120.51 (17)
C5—C6—C1	118.84 (15)	C13—C14—H14A	119.7
C5—C6—C7	118.98 (14)	C15—C14—H14A	119.7
C1—C6—C7	122.17 (14)	O4—C15—C14	123.15 (14)
O1—C7—C6	121.98 (15)	O4—C15—C10	117.17 (14)
O1—C7—C8	120.12 (15)	C14—C15—C10	119.67 (15)
C6—C7—C8	117.90 (13)	O4—C16—H16A	109.5
O2—C8—C7	111.06 (14)	O4—C16—H16B	109.5
O2—C8—H8A	109.4	H16A—C16—H16B	109.5
C7—C8—H8A	109.4	O4—C16—H16C	109.5
O2—C8—H8B	109.4	H16A—C16—H16C	109.5
C7—C8—H8B	109.4	H16B—C16—H16C	109.5

C6—C1—C2—C3	0.0 (2)	C8—O2—C9—C10	170.17 (13)
C1—C2—C3—C4	0.2 (2)	O3—C9—C10—C11	170.24 (16)
C1—C2—C3—Cl1	179.21 (12)	O2—C9—C10—C11	−10.50 (19)
C2—C3—C4—C5	−0.2 (2)	O3—C9—C10—C15	−9.9 (2)
Cl1—C3—C4—C5	−179.21 (12)	O2—C9—C10—C15	169.40 (13)
C3—C4—C5—C6	0.0 (2)	C15—C10—C11—C12	−0.7 (2)
C4—C5—C6—C1	0.2 (2)	C9—C10—C11—C12	179.24 (15)
C4—C5—C6—C7	179.14 (14)	C10—C11—C12—C13	0.1 (3)
C2—C1—C6—C5	−0.2 (2)	C11—C12—C13—C14	0.4 (3)
C2—C1—C6—C7	−179.12 (14)	C12—C13—C14—C15	−0.3 (3)
C5—C6—C7—O1	4.4 (2)	C16—O4—C15—C14	−1.0 (2)
C1—C6—C7—O1	−176.70 (15)	C16—O4—C15—C10	179.95 (16)
C5—C6—C7—C8	−175.29 (13)	C13—C14—C15—O4	−179.34 (15)
C1—C6—C7—C8	3.6 (2)	C13—C14—C15—C10	−0.3 (2)
C9—O2—C8—C7	−77.10 (17)	C11—C10—C15—O4	179.86 (13)
O1—C7—C8—O2	5.8 (2)	C9—C10—C15—O4	0.0 (2)
C6—C7—C8—O2	−174.59 (12)	C11—C10—C15—C14	0.7 (2)
C8—O2—C9—O3	−10.5 (2)	C9—C10—C15—C14	−179.15 (14)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2A···O1ⁱ	0.93	2.40	3.301 (2)	164

Symmetry code: (i) x+1, y, z.

Experimental details

Crystal data
Chemical formula	C₁₆H₁₃ClO₄
M_r	304.71
Crystal system, space group	Orthorhombic, Pbca
Temperature (K)	296
a, b, c (Å)	7.7207 (6), 14.4411 (12), 26.064 (2)
V (Å³)	2906.0 (4)
Z	8
Radiation type	Mo Kα
µ (mm⁻¹)	0.28
Crystal size (mm)	0.51 × 0.29 × 0.19

Data collection
Diffractometer	Bruker APEXII DUO CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2009)
T_min, T_max	0.829, 0.950
No. of measured, independent and observed [I > 2σ(I)] reflections	16215, 4027, 2731
R_int	0.025
(sin θ/λ)_max (Å⁻¹)	0.693

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.041, 0.116, 1.02
No. of reflections	4027
No. of parameters	190
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.17, −0.35

Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2A···O1ⁱ	0.9300	2.4000	3.301 (2)	164.00

Symmetry code: (i) x+1, y, z.

Footnotes

‡Thomson Reuters ResearcherID: A-3561-2009.

Acknowledgements

HKF and SIJA thank Universiti Sains Malaysia for the Research University Grants (Nos. 1001/PFIZIK/811160 and 1001/PFIZIK/811151). AMI is grateful to the Department of Atomic Energy, Board for Research in Nuclear Sciences, Government of India for the Young Scientist award. BG thanks the Department of Information Technology, New Delhi, India for financial support.

References

Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19. CrossRef Web of Science Google Scholar
Bruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Gandhi, S. S., Bell, K. L. & Gibson, M. S. (1995). Tetrahedron, 51, 13301–13308. CrossRef CAS Web of Science Google Scholar
Huang, W., Pian, J., Chen, B., Pei, W. & Ye, X. (1996). Tetrahedron, 52, 10131–10136. CrossRef CAS Web of Science Google Scholar
Litera, J. K., Loya, A. D. & Klan, P. (2006). J. Org. Chem. 71, 713–723. Web of Science PubMed Google Scholar
Rather, J. B. & Reid, E. (1919). J. Am. Chem. Soc. 41, 75–83. CrossRef CAS Google Scholar
Ruzicka, R., Zabadal, M. & Klan, P. (2002). Synth. Commun. 32, 2581–2590. Web of Science CrossRef CAS Google Scholar
Sheehan, J. C. & Umezaw, K. (1973). J. Org. Chem. 58, 3771–3773. CrossRef Web of Science 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