1-{5-[2-Chloro-5-(trifluoro­meth­yl)phen­yl]thio­phen-2-yl}ethanone

Lytvyn, R.; Horak, Y.; Matiychuk, V.; Obushak, M.; Kinzhybalo, V.

doi:10.1107/S1600536811003965

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 67| Part 3| March 2011| Page o585

doi:10.1107/S1600536811003965

Open

access

1-{5-[2-Chloro-5-(trifluoromethyl)phenyl]thiophen-2-yl}ethanone

Roman Lytvyn,^a Yuri Horak,^a ^* Vasyl Matiychuk,^a Mykola Obushak ^a and Vasyl Kinzhybalo ^b

^aDepartment of Organic Chemistry, Ivan Franko National University of Lviv, Kyryla and Mefodiya 6, Lviv 79005, Ukraine, and ^bFaculty of Chemistry, University of Wrocław, 14 Joliot-Curie St, 50-383 Wrocław, Poland
^*Correspondence e-mail: horrak@gmail.com

(Received 11 January 2011; accepted 31 January 2011; online 9 February 2011)

In the title molecule, C₁₃H₈ClF₃OS, the dihedral angle between the mean planes of 2-chloro-5-(trifluoromethyl)phenyl and tiophene rings is 54.37 (5)°. The acethyl group is twisted by 8.1 (2)° with respect to the thiophene ring. The CF₃ group is disordered over two sets of sites with occupations of 0.49 (3) and 0.51 (3). The crystal packing features C—H⋯F and C—H⋯O hydrogen bonds, forming dimers which are connected into chains along the c axis by C—H⋯O hydrogen bonds and C—Cl⋯π [Cl⋯π = 3.415 (1) Å and C—Cl⋯π = 151.56 (5)°] interactions. The chains are further connected into layers perpendicular to the a axis by C—H⋯O interactions.

Related literature

For the general synthetic procedure, see: Matiychuk et al. (2010 ). For the biologial activity of arylthiophenes, see: Reddy et al. (2005 ); Anderson et al. (1963 ); Bohlmann et al. (1984 ); Michaelides et al. (1997 ); Tanaka et al. (1998 ) and for their applications, see Masui et al. (2004 ); Roncali (1992 , 1997 ). For methods of obtaining arylthiophenes via cross-coupling reactions, see: Stanforth (1998 ).

Experimental

Crystal data

C₁₃H₈ClF₃OS
M_r = 304.70
Monoclinic, P 2₁ /c
a = 15.330 (6) Å
b = 10.809 (4) Å
c = 7.676 (3) Å
β = 93.72 (3)°
V = 1269.3 (8) Å³
Z = 4
Mo Kα radiation
μ = 0.49 mm⁻¹
T = 100 K
0.20 × 0.15 × 0.08 mm

Data collection

Kuma KM-4-CCD diffractometer
Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2006 $[Oxford Diffraction (2006). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Wrocław, Poland.]$ ) T_min = 0.86, T_max = 0.93
16021 measured reflections
4377 independent reflections
3093 reflections with I > 2σ(I)
R_int = 0.034

Refinement

R[F² > 2σ(F²)] = 0.039
wR(F²) = 0.097
S = 1.00
4377 reflections
201 parameters
H-atom parameters constrained
Δρ_max = 0.49 e Å⁻³
Δρ_min = −0.25 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C22—H22C⋯F1Aⁱ	0.98	2.55	3.520 (13)	168
C22—H22B⋯O1ⁱⁱ	0.98	2.62	3.526 (2)	154
C22—H22A⋯O1ⁱⁱⁱ	0.98	2.67	3.562 (3)	152
C56—H56⋯O1ⁱ	0.95	2.78	3.697 (2)	162
Symmetry codes: (i) -x+1, -y+1, -z+2; (ii) $[-x+1, y-{\script{1\over 2}}, -z+{\script{5\over 2}}]$ ; (iii) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ .

Data collection: CrysAlis CCD (Oxford Diffraction, 2006 $[Oxford Diffraction (2006). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Wrocław, Poland.]$ ); cell refinement: CrysAlis RED (Oxford Diffraction, 2006 $[Oxford Diffraction (2006). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Wrocław, Poland.]$ ); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811003965/ds2088sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811003965/ds2088Isup2.hkl

checkCIF report

Comment top

Arylthiophenes and their homologues are an important class of organic compounds. The arylthiophenes units are represented in several types of compounds of current interest including polymers (Roncali, 1992; Roncali, 1997), liquid crystals (Masui et al., 2004), ligands and molecules of medicinal interest (Michaelides et al., 1997; Tanaka et al., 1998; Reddy et al., 2005; Anderson et al., 1963). In view of the arylthiophenes importance a number of catalytic methods of these compounds formation from precursors in a cross-coupling reactions have been developed over the last two decades (Stanforth, 1998). However, these methods proceed in two steps via an organometallic intermediate and their stability is often limited.

The molecule of the title compound is not plannar (see Fig. 1). The dihedral angle between the mean planes of 2-chloro-5-(trifluoromethyl)phenyl and tiophene rings is equal to 54.37 (5)°. The acethyl group is twisted with respect to the tiophene ring by 8.1 (2)°. The CF₃ group is disordered with almoust equal occupations of two positions, which are realised by the rotation around C1–C55 bond. The crystal structure packing is governed by the hydrogen bonds of C–H···F and C–H···O types and C–Cl···π interactions. The centrosymmetric dimers are formed by the pairs of C22–H22C···F1Aⁱ and C56–H56···O1ⁱ hydrogen bonds. The dimers are connected into the chains that propagate along z axis direction by means of C22–H22A···O1ⁱⁱⁱ hydrogen bonds and C52–Cl1···C_g^iv interactions (symmetry code: (iv) x, 1/2 - y, z + 1/2). The geometrical parameters of C52–Cl1···C_g^iv interaction are as follows: Cl1···C_g^iv distance is equal to 3.415 (1) Å and the C52–Cl1···C_g^iv angle 151.56 (5)°. The vast layers perpendicular to x axis direction are formed of above mentioned chains connected with each other by C22–H22B···O1ⁱⁱ hydrogen bonds (see Fig. 2).

Related literature top

For the general synthetic procedure, see: Matiychuk et al. (2010). For the biologial activity of arylthiophenes, see: Reddy et al. (2005); Anderson et al. (1963); Bohlmann et al. (1984); Michaelides et al. (1997); Tanaka et al. (1998) and for their applications, see Masui et al. (2004); Roncali (1992, 1997). For methods of obtaining arylthiophenes via cross-coupling reactions, see: Stanforth (1998).

Experimental top

Water solution of 7 g of NaNO₂ (25 ml) was added dropwise to a cooled stirred mixture of 2-chloro-5-trifluoromethylaniline (19.5 g, 0.1 mol, Fluka) and 60 ml of 20% HCl. After completion of reaction the solution was filtered and added dropwise to well stirred mixture of 2-acetylthiophene (12.6 g, 0.1 mol, Fluka), acetone (40 ml) and CuCl₂^.2H₂O (1.5 g, 8.7 mmol) during 20 min. After 3 h the reaction mixture was diluted with 250 ml of water and 50 ml of CHCl₃, organic layer was separated and dried over Na₂SO₄, and concentrated under reduced pressure. Residue was distilled at 400 Pa (453–458 K) and gave 11.6 g (38% yield) of 1-{5-[2-chloro-5-(trifluoromethyl)phenyl]-2-thienyl}ethanone. Yellow crystals suitable for X-ray analysis were obtained by recrystallization from n-hexane.

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top

	Fig. 1. Asymmetric unit of the crystal alnog with atom labeling scheme. The thermal ellipsoids are drawn at the 50% probability level.
	Fig. 2. The packing of the title compound along with intermolecular hydrogen bonds.

1-{5-[2-Chloro-5-(trifluoromethyl)phenyl]thiophen-2-yl}ethanone top

Crystal data top

C₁₃H₈ClF₃OS	F(000) = 616
M_r = 304.70	D_x = 1.594 Mg m⁻³
Monoclinic, P2₁/c	Melting point: 347 K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 15.330 (6) Å	Cell parameters from 11592 reflections
b = 10.809 (4) Å	θ = 2.3–33.9°
c = 7.676 (3) Å	µ = 0.49 mm⁻¹
β = 93.72 (3)°	T = 100 K
V = 1269.3 (8) Å³	Block, colourless
Z = 4	0.20 × 0.15 × 0.08 mm

Data collection top

Kuma KM-4-CCD diffractometer	4377 independent reflections
Radiation source: fine-focus sealed tube	3093 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.034
ω scans	θ_max = 33.8°, θ_min = 3.3°
Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2006)	h = −19→23
T_min = 0.86, T_max = 0.93	k = −12→16
16021 measured reflections	l = −11→9

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) = 0.097	H-atom parameters constrained
S = 1.00	w = 1/[σ²(F_o²) + (0.054P)²] where P = (F_o² + 2F_c²)/3
4377 reflections	(Δ/σ)_max = 0.001
201 parameters	Δρ_max = 0.49 e Å⁻³
0 restraints	Δρ_min = −0.25 e Å⁻³

Crystal data top

C₁₃H₈ClF₃OS	V = 1269.3 (8) Å³
M_r = 304.70	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 15.330 (6) Å	µ = 0.49 mm⁻¹
b = 10.809 (4) Å	T = 100 K
c = 7.676 (3) Å	0.20 × 0.15 × 0.08 mm
β = 93.72 (3)°

Data collection top

Kuma KM-4-CCD diffractometer	4377 independent reflections
Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2006)	3093 reflections with I > 2σ(I)
T_min = 0.86, T_max = 0.93	R_int = 0.034
16021 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.039	0 restraints
wR(F²) = 0.097	H-atom parameters constrained
S = 1.00	Δρ_max = 0.49 e Å⁻³
4377 reflections	Δρ_min = −0.25 e Å⁻³
201 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	Occ. (<1)
Cl1	0.09807 (2)	0.28619 (3)	1.05277 (5)	0.02440 (10)
S1	0.37102 (2)	0.42596 (3)	1.04508 (5)	0.01971 (9)
O1	0.54239 (7)	0.39388 (9)	1.24469 (14)	0.0261 (2)
C2	0.42729 (9)	0.29067 (12)	1.08963 (19)	0.0181 (3)
C21	0.51398 (9)	0.29623 (12)	1.18365 (19)	0.0208 (3)
C22	0.56531 (10)	0.17781 (14)	1.1983 (2)	0.0276 (3)
H22A	0.5812	0.1521	1.0821	0.041*
H22B	0.5297	0.1133	1.2485	0.041*
H22C	0.6185	0.1909	1.2738	0.041*
C3	0.37969 (9)	0.18899 (12)	1.02942 (19)	0.0194 (3)
H3	0.4000	0.1062	1.0413	0.023*
C4	0.29753 (9)	0.22147 (12)	0.94833 (19)	0.0192 (3)
H4	0.2562	0.1630	0.9010	0.023*
C5	0.28396 (9)	0.34750 (11)	0.94559 (18)	0.0160 (3)
C51	0.20972 (9)	0.41760 (11)	0.86157 (18)	0.0164 (3)
C52	0.12277 (9)	0.39514 (12)	0.89694 (18)	0.0179 (3)
C53	0.05343 (9)	0.45875 (12)	0.81028 (19)	0.0192 (3)
H53	−0.0051	0.4413	0.8357	0.023*
C54	0.07070 (9)	0.54733 (12)	0.68726 (19)	0.0198 (3)
H54	0.0241	0.5907	0.6270	0.024*
C55	0.15699 (9)	0.57247 (12)	0.65236 (18)	0.0192 (3)
C1	0.17567 (10)	0.66394 (15)	0.5124 (2)	0.0289 (4)
F1	0.2540 (6)	0.7124 (13)	0.528 (2)	0.049 (3)	0.49 (3)
F2	0.1209 (7)	0.7645 (7)	0.5195 (13)	0.0485 (17)	0.49 (3)
F3	0.1634 (9)	0.6244 (10)	0.3552 (8)	0.059 (2)	0.49 (3)
F1A	0.2471 (7)	0.7292 (12)	0.549 (2)	0.052 (2)	0.51 (3)
F2A	0.1125 (5)	0.7352 (16)	0.465 (2)	0.070 (3)	0.51 (3)
F3A	0.1942 (11)	0.5975 (8)	0.3643 (11)	0.079 (2)	0.51 (3)
C56	0.22588 (9)	0.50955 (12)	0.73913 (18)	0.0189 (3)
H56	0.2843	0.5290	0.7153	0.023*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.01931 (18)	0.02759 (17)	0.0267 (2)	−0.00030 (13)	0.00436 (14)	0.00743 (14)
S1	0.01739 (17)	0.01659 (14)	0.0246 (2)	−0.00050 (12)	−0.00288 (13)	0.00172 (13)
O1	0.0217 (5)	0.0253 (5)	0.0307 (6)	−0.0040 (4)	−0.0041 (5)	0.0034 (4)
C2	0.0151 (6)	0.0200 (6)	0.0193 (7)	0.0012 (5)	0.0017 (5)	0.0023 (5)
C21	0.0178 (7)	0.0234 (6)	0.0214 (8)	−0.0002 (5)	0.0024 (6)	0.0072 (5)
C22	0.0194 (7)	0.0266 (7)	0.0362 (10)	0.0026 (6)	−0.0034 (7)	0.0065 (6)
C3	0.0184 (7)	0.0194 (6)	0.0208 (7)	0.0027 (5)	0.0033 (6)	0.0005 (5)
C4	0.0201 (7)	0.0185 (6)	0.0189 (7)	−0.0012 (5)	0.0009 (6)	−0.0014 (5)
C5	0.0154 (6)	0.0177 (5)	0.0149 (7)	−0.0002 (5)	0.0009 (5)	−0.0005 (5)
C51	0.0164 (6)	0.0170 (5)	0.0158 (7)	0.0011 (5)	0.0002 (5)	−0.0031 (5)
C52	0.0185 (7)	0.0190 (5)	0.0163 (7)	0.0000 (5)	0.0009 (5)	−0.0009 (5)
C53	0.0138 (6)	0.0234 (6)	0.0203 (7)	0.0012 (5)	0.0007 (5)	−0.0041 (5)
C54	0.0182 (7)	0.0217 (6)	0.0190 (7)	0.0028 (5)	−0.0027 (6)	−0.0021 (5)
C55	0.0200 (7)	0.0200 (6)	0.0174 (7)	0.0005 (5)	0.0005 (5)	0.0003 (5)
C1	0.0219 (8)	0.0343 (8)	0.0300 (9)	0.0007 (6)	−0.0013 (7)	0.0102 (7)
F1	0.015 (2)	0.068 (5)	0.062 (5)	0.000 (3)	−0.003 (2)	0.043 (4)
F2	0.050 (3)	0.038 (2)	0.059 (4)	0.0255 (18)	0.020 (2)	0.0291 (19)
F3	0.115 (6)	0.043 (3)	0.0173 (15)	−0.024 (3)	−0.005 (2)	0.0037 (17)
F1A	0.053 (5)	0.049 (3)	0.053 (3)	−0.029 (3)	−0.008 (3)	0.022 (2)
F2A	0.0206 (16)	0.093 (6)	0.099 (7)	0.016 (3)	0.010 (3)	0.074 (5)
F3A	0.160 (6)	0.051 (2)	0.029 (2)	0.010 (4)	0.037 (3)	0.0148 (18)
C56	0.0169 (7)	0.0211 (6)	0.0189 (7)	−0.0004 (5)	0.0018 (5)	−0.0017 (5)

Geometric parameters (Å, º) top

Cl1—C52	1.738 (2)	C51—C56	1.401 (2)
S1—C5	1.718 (2)	C52—C53	1.398 (2)
S1—C2	1.721 (2)	C53—C54	1.382 (2)
O1—C21	1.224 (2)	C53—H53	0.9500
C2—C3	1.382 (2)	C54—C55	1.393 (2)
C2—C21	1.472 (2)	C54—H54	0.9500
C21—C22	1.503 (2)	C55—C56	1.389 (2)
C22—H22A	0.9800	C55—C1	1.501 (2)
C22—H22B	0.9800	C1—F2A	1.272 (8)
C22—H22C	0.9800	C1—F3	1.282 (8)
C3—C4	1.413 (2)	C1—F1	1.309 (10)
C3—H3	0.9500	C1—F1A	1.317 (11)
C4—C5	1.378 (2)	C1—F2	1.377 (7)
C4—H4	0.9500	C1—F3A	1.389 (8)
C5—C51	1.480 (2)	C56—H56	0.9500
C51—C52	1.399 (2)

C5—S1—C2	91.94 (7)	C53—C52—Cl1	117.91 (11)
C3—C2—C21	129.54 (12)	C51—C52—Cl1	120.28 (11)
C3—C2—S1	111.25 (11)	C54—C53—C52	119.50 (13)
C21—C2—S1	119.20 (10)	C54—C53—H53	120.3
O1—C21—C2	120.70 (13)	C52—C53—H53	120.3
O1—C21—C22	122.31 (14)	C53—C54—C55	119.52 (13)
C2—C21—C22	116.98 (12)	C53—C54—H54	120.2
C21—C22—H22A	109.5	C55—C54—H54	120.2
C21—C22—H22B	109.5	C56—C55—C54	120.92 (13)
H22A—C22—H22B	109.5	C56—C55—C1	119.42 (13)
C21—C22—H22C	109.5	C54—C55—C1	119.58 (13)
H22A—C22—H22C	109.5	F3—C1—F1	107.4 (8)
H22B—C22—H22C	109.5	F2A—C1—F1A	110.1 (7)
C2—C3—C4	112.70 (12)	F3—C1—F2	104.4 (6)
C2—C3—H3	123.7	F1—C1—F2	103.8 (7)
C4—C3—H3	123.7	F2A—C1—F3A	105.6 (6)
C5—C4—C3	112.45 (12)	F1A—C1—F3A	103.8 (8)
C5—C4—H4	123.8	F2A—C1—C55	115.3 (4)
C3—C4—H4	123.8	F3—C1—C55	115.5 (4)
C4—C5—C51	128.60 (12)	F1—C1—C55	114.4 (6)
C4—C5—S1	111.66 (10)	F1A—C1—C55	113.4 (6)
C51—C5—S1	119.62 (10)	F2—C1—C55	110.3 (4)
C52—C51—C56	117.75 (12)	F3A—C1—C55	107.7 (4)
C52—C51—C5	122.83 (12)	C55—C56—C51	120.46 (13)
C56—C51—C5	119.41 (12)	C55—C56—H56	119.8
C53—C52—C51	121.81 (13)	C51—C56—H56	119.8

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C22—H22C···F1Aⁱ	0.98	2.55	3.520 (13)	168
C22—H22B···O1ⁱⁱ	0.98	2.62	3.526 (2)	154
C22—H22A···O1ⁱⁱⁱ	0.98	2.67	3.562 (3)	152
C56—H56···O1ⁱ	0.95	2.78	3.697 (2)	162

Symmetry codes: (i) −x+1, −y+1, −z+2; (ii) −x+1, y−1/2, −z+5/2; (iii) x, −y+1/2, z−1/2.

Experimental details

Crystal data
Chemical formula	C₁₃H₈ClF₃OS
M_r	304.70
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	15.330 (6), 10.809 (4), 7.676 (3)
β (°)	93.72 (3)
V (Å³)	1269.3 (8)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.49
Crystal size (mm)	0.20 × 0.15 × 0.08

Data collection
Diffractometer	Kuma KM-4-CCD diffractometer
Absorption correction	Analytical (CrysAlis RED; Oxford Diffraction, 2006)
T_min, T_max	0.86, 0.93
No. of measured, independent and observed [I > 2σ(I)] reflections	16021, 4377, 3093
R_int	0.034
(sin θ/λ)_max (Å⁻¹)	0.782

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.039, 0.097, 1.00
No. of reflections	4377
No. of parameters	201
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.49, −0.25

Computer programs: CrysAlis CCD (Oxford Diffraction, 2006), CrysAlis RED (Oxford Diffraction, 2006), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2006), publCIF (Westrip, 2010).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C22—H22C···F1Aⁱ	0.98	2.55	3.520 (13)	168
C22—H22B···O1ⁱⁱ	0.98	2.62	3.526 (2)	154
C22—H22A···O1ⁱⁱⁱ	0.98	2.67	3.562 (3)	152
C56—H56···O1ⁱ	0.95	2.78	3.697 (2)	162

Symmetry codes: (i) −x+1, −y+1, −z+2; (ii) −x+1, y−1/2, −z+5/2; (iii) x, −y+1/2, z−1/2.

Acknowledgements

The authors acknowledge Professor T. Lis (University of Wroclaw) for providing the X-ray data collection faciltities.

References

Anderson, E. L., Casey, J. E., Emas, M., Force, E. E., Jensen, E. M., Matz, R. S. & Rivard, D. E. (1963). J. Med. Chem. 6, 787–791. CrossRef PubMed CAS Web of Science Google Scholar
Bohlmann, F., Knauf, W. & Misra, L. N. (1984). Tetrahedron, 40, 4987–4989. CrossRef CAS Web of Science Google Scholar
Brandenburg, K. (2006). DIAMOND. Crystal Impact GbR, Bonn, Germany. Google Scholar
Masui, K., Mori, A., Okano, K., Takamura, K., Kinoshita, M. & Ikeda, T. (2004). Org. Lett. 6, 2011–2014. Web of Science CrossRef PubMed CAS Google Scholar
Matiychuk, V. S., Obushak, N. D., Lytvyn, R. Z. & Horak, Yu. I. (2010). Chem. Heterocycl. Compd, 46, 50–55. CrossRef CAS Google Scholar
Michaelides, M. R., Hong, Yu., DiDomenico, S., Bayburt, E. K., Asin, K. E., Britton, D. R., Wel Lin, Ch. & Shiosaki, K. (1997). J. Med. Chem. 40, 1585–1599. CrossRef CAS PubMed Web of Science Google Scholar
Oxford Diffraction (2006). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Wrocław, Poland. Google Scholar
Reddy, T. J., Leclair, M. & Proulx, M. (2005). Synlett, 4, 583–586. Web of Science CrossRef Google Scholar
Roncali, J. (1992). Chem. Rev. 92, 711–738. CrossRef CAS Web of Science Google Scholar
Roncali, J. (1997). Chem. Rev. 97, 173–205. CrossRef PubMed CAS Web of Science Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Stanforth, S. P. (1998). Tetrahedron, 54, 263–303. Web of Science CrossRef CAS Google Scholar
Tanaka, A., Terasawa, T., Hagihara, H., Sakumi, Yu., Ishibe, N., Sawada, M., Takasugi, H. & Tanaka, H. (1998). J. Med. Chem. 41, 2390–2410. Web of Science CrossRef CAS PubMed Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar