1,3,5-Tris(6-chloro­pyrazin-2-yl­oxy)benzene

Li, Y.; Wang, J.-W.

doi:10.1107/S160053680706360X

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 64| Part 1| January 2008| Page o168

https://doi.org/10.1107/S160053680706360X

Open

access

1,3,5-Tris(6-chloropyrazin-2-yloxy)benzene

Yan Li ^a and Jian-Wu Wang ^a ^*

^aSchool of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, People's Republic of China
^*Correspondence e-mail: yugp2005@yahoo.com.cn

(Received 19 November 2007; accepted 26 November 2007; online 6 December 2007)

In the title compound, C₁₈H₉Cl₃N₆O₃, all bond lengths and angles are normal. The dihedral angles between the benzene ring and the three pyrazine rings are 72.67 (2), 60.73 (3) and 77.74 (2)°. The crystal packing is stabilized by van der Waals forces and by a weak π–π stacking interaction between pyrazine rings, with a centroid–centroid distance of 3.487 (2) Å.

Related literature

For related literatures see: Carter & Boer (1974 ); Seitz et al. (2002 ); Temple et al. (1970 ).

Experimental

Crystal data

C₁₈H₉Cl₃N₆O₃
M_r = 463.66
Triclinic, $[P \overline 1]$
a = 9.680 (2) Å
b = 10.658 (2) Å
c = 11.039 (3) Å
α = 72.768 (3)°
β = 68.308 (3)°
γ = 69.342 (3)°
V = 972.0 (4) Å³
Z = 2
Mo Kα radiation
μ = 0.51 mm⁻¹
T = 298 (2) K
0.58 × 0.31 × 0.30 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2004 ) T_min = 0.758, T_max = 0.863
4925 measured reflections
3375 independent reflections
2797 reflections with I > 2σ(I)
R_int = 0.017

Refinement

R[F² > 2σ(F²)] = 0.041
wR(F²) = 0.108
S = 1.04
3375 reflections
271 parameters
H-atom parameters constrained
Δρ_max = 0.22 e Å⁻³
Δρ_min = −0.39 e Å⁻³

Data collection: SMART (Bruker, 2001 ); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2001 ); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and local programs.

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S160053680706360X/fj2085sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S160053680706360X/fj2085Isup2.hkl

checkCIF report

Comment top

Pyrazine derivatives were shown to display antimycobacterial (Seitz et al., 2002) and potential antimalarial (Temple et al., 1970) activities. The title compound was prepared for the screening of these bioactivities. We report here the crystal structure of (I).

In (I) (Fig. 1), all bond lengths and angles are normal and in a good agreement with those reported previously (Carter & Boer, 1974). The dihedral angles between benzene ring (C1—C6) and three Pyrazine rings (C7—C10/N1/N2; C11—C14/N3/N4; C15—C18/N5/N6) are 72.67 (2), 60.73 (3) and 77.74 (2)°, respectively. The crystal packing is stabilized by weak π–π stacking interactions and van der Waals forces, proved by the shorter distance Cg1···Cg1ⁱⁱ of 3.487 (2) Å, where Cg1 is a centroid of Pyrazine ring (C11—C14/N3/N4) [symmetry code:(ii) –X,1-Y,2-Z].

Related literature top

For related literatures see: Carter & Boer (1974); Seitz et al. (2002); Temple et al. (1970).

Experimental top

A flask was charged with 1.26 g (10 mmol) of 1,3,5-trihydroxybenzene, 4.47 g (30 mmol) of 2,6-dichloropyrazine and 3.18 g (30 mmol) of sodium carbonate, followed by addition of 50 ml of dried MeCN. The resultant mixture was refluxed over night. On cooling, the reaction mixture was filtered and the filtrate was portioned between 150 ml of water and 200 ml of dichloromethane. The organic phase was washed with brine, dried over sodium sulfate and evaporated on a rotary evaporator to furnish the crude product as a residue, which was chromatographed on silica gel to afford the pure product as colorless prisms. Crystals suitable for X-ray diffraction were obtained via slow evaporation of a solution of the title compound in ethyl acetate.

Structure description top

For related literatures see: Carter & Boer (1974); Seitz et al. (2002); Temple et al. (1970).

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXTL (Sheldrick, 2001); program(s) used to refine structure: SHELXTL (Sheldrick, 2001); molecular graphics: SHELXTL (Sheldrick, 2001); software used to prepare material for publication: SHELXTL and local programs.

Figures top

Fig. 1. View of the title compound (I), with displacement ellipsoids drawn at the 40% probability level.

1,3,5-Tris(6-chloropyrazin-2-yloxy)benzene top

Crystal data top

C₁₈H₉Cl₃N₆O₃	Z = 2
M_r = 463.66	F(000) = 468
Triclinic, P1	D_x = 1.584 Mg m⁻³
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 9.680 (2) Å	Cell parameters from 1699 reflections
b = 10.658 (2) Å	θ = 2.8–23.1°
c = 11.039 (3) Å	µ = 0.51 mm⁻¹
α = 72.768 (3)°	T = 298 K
β = 68.308 (3)°	Prism, colorless
γ = 69.342 (3)°	0.58 × 0.31 × 0.30 mm
V = 972.0 (4) Å³

Data collection top

Bruker SMART CCD area-detector diffractometer	3375 independent reflections
Radiation source: fine-focus sealed tube	2797 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.017
φ and ω scans	θ_max = 25.0°, θ_min = 2.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 2004)	h = −9→11
T_min = 0.758, T_max = 0.863	k = −12→12
4925 measured reflections	l = −13→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)] = 0.041	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.108	H-atom parameters constrained
S = 1.04	w = 1/[σ²(F_o²) + (0.0537P)² + 0.2339P] where P = (F_o² + 2F_c²)/3
3375 reflections	(Δ/σ)_max = 0.001
271 parameters	Δρ_max = 0.22 e Å⁻³
0 restraints	Δρ_min = −0.39 e Å⁻³

Crystal data top

C₁₈H₉Cl₃N₆O₃	γ = 69.342 (3)°
M_r = 463.66	V = 972.0 (4) Å³
Triclinic, P1	Z = 2
a = 9.680 (2) Å	Mo Kα radiation
b = 10.658 (2) Å	µ = 0.51 mm⁻¹
c = 11.039 (3) Å	T = 298 K
α = 72.768 (3)°	0.58 × 0.31 × 0.30 mm
β = 68.308 (3)°

Data collection top

Bruker SMART CCD area-detector diffractometer	3375 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 2004)	2797 reflections with I > 2σ(I)
T_min = 0.758, T_max = 0.863	R_int = 0.017
4925 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.041	0 restraints
wR(F²) = 0.108	H-atom parameters constrained
S = 1.04	Δρ_max = 0.22 e Å⁻³
3375 reflections	Δρ_min = −0.39 e Å⁻³
271 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	0.04661 (7)	0.67966 (7)	0.44208 (6)	0.0642 (2)
Cl2	0.43548 (9)	1.27994 (7)	−0.59901 (7)	0.0772 (2)
Cl3	0.32169 (10)	1.47146 (8)	0.07383 (9)	0.0893 (3)
O1	0.43622 (16)	0.85408 (15)	0.05573 (15)	0.0530 (4)
O2	0.1867 (2)	0.93858 (16)	−0.27062 (15)	0.0616 (4)
O3	−0.01216 (16)	1.23869 (14)	0.03280 (16)	0.0513 (4)
N1	−0.1102 (3)	1.4653 (2)	0.2505 (2)	0.0743 (6)
N2	0.4938 (2)	0.6220 (2)	0.3517 (2)	0.0701 (6)
N3	0.2331 (3)	1.0283 (2)	−0.6181 (2)	0.0672 (6)
N4	0.1437 (2)	1.34503 (17)	0.05891 (17)	0.0469 (4)
N5	0.3057 (2)	1.09657 (17)	−0.42807 (17)	0.0459 (4)
N6	0.25692 (18)	0.76867 (16)	0.23874 (16)	0.0409 (4)
C1	0.0239 (4)	1.4929 (3)	0.2147 (3)	0.0718 (8)
H1B	0.0338	1.5541	0.2539	0.086*
C2	0.3070 (3)	1.1226 (3)	−0.6499 (2)	0.0600 (6)
H2B	0.3358	1.1674	−0.7377	0.072*
C3	−0.1181 (3)	1.3782 (3)	0.1916 (2)	0.0610 (6)
H3B	−0.2104	1.3560	0.2147	0.073*
C4	0.5191 (3)	0.7021 (3)	0.2337 (2)	0.0626 (7)
H4B	0.6188	0.7094	0.1867	0.075*
C5	0.1484 (3)	1.4320 (2)	0.1203 (2)	0.0542 (6)
C6	0.1940 (3)	0.9688 (3)	−0.4911 (2)	0.0602 (6)
H6B	0.1415	0.9025	−0.4643	0.072*
C7	0.3414 (2)	1.1549 (2)	−0.5553 (2)	0.0488 (5)
C8	0.2308 (3)	1.0047 (2)	−0.3975 (2)	0.0470 (5)
C9	0.3493 (3)	0.6156 (2)	0.4159 (2)	0.0540 (6)
H9A	0.3264	0.5614	0.5000	0.065*
C10	0.2025 (3)	0.9832 (2)	−0.1693 (2)	0.0467 (5)
C11	0.3125 (2)	0.8988 (2)	−0.1081 (2)	0.0467 (5)
H11A	0.3812	0.8202	−0.1386	0.056*
C12	0.2348 (2)	0.68880 (19)	0.3581 (2)	0.0407 (5)
C13	0.3169 (2)	0.9348 (2)	−0.0002 (2)	0.0421 (5)
C14	0.0097 (2)	1.3191 (2)	0.0952 (2)	0.0440 (5)
C15	0.1076 (2)	1.12977 (19)	−0.0168 (2)	0.0403 (5)
C16	0.2156 (2)	1.0492 (2)	0.0488 (2)	0.0409 (4)
H16A	0.2196	1.0713	0.1226	0.049*
C17	0.0996 (2)	1.0992 (2)	−0.1265 (2)	0.0444 (5)
H17A	0.0268	1.1553	−0.1699	0.053*
C18	0.3995 (2)	0.77556 (19)	0.1787 (2)	0.0419 (5)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.0539 (3)	0.0787 (4)	0.0503 (4)	−0.0223 (3)	−0.0150 (3)	0.0057 (3)
Cl2	0.1024 (5)	0.0756 (4)	0.0561 (4)	−0.0460 (4)	−0.0100 (4)	−0.0072 (3)
Cl3	0.0920 (5)	0.0802 (5)	0.1186 (7)	−0.0405 (4)	−0.0433 (5)	−0.0155 (4)
O1	0.0408 (8)	0.0582 (9)	0.0452 (9)	−0.0084 (7)	−0.0133 (7)	0.0055 (7)
O2	0.0966 (13)	0.0628 (10)	0.0390 (9)	−0.0401 (9)	−0.0227 (8)	−0.0036 (7)
O3	0.0463 (8)	0.0467 (8)	0.0619 (10)	−0.0073 (6)	−0.0212 (7)	−0.0118 (7)
N1	0.0842 (17)	0.0791 (15)	0.0478 (13)	−0.0113 (13)	−0.0091 (11)	−0.0225 (11)
N2	0.0501 (12)	0.0856 (15)	0.0539 (13)	−0.0002 (10)	−0.0244 (10)	0.0053 (11)
N3	0.0846 (15)	0.0855 (15)	0.0436 (12)	−0.0288 (12)	−0.0243 (11)	−0.0158 (11)
N4	0.0521 (10)	0.0416 (9)	0.0439 (10)	−0.0120 (8)	−0.0150 (8)	−0.0040 (8)
N5	0.0531 (10)	0.0477 (10)	0.0367 (10)	−0.0103 (8)	−0.0156 (8)	−0.0090 (8)
N6	0.0451 (10)	0.0397 (9)	0.0361 (9)	−0.0061 (7)	−0.0174 (8)	−0.0044 (7)
C1	0.105 (2)	0.0596 (15)	0.0553 (16)	−0.0137 (15)	−0.0331 (16)	−0.0168 (13)
C2	0.0684 (15)	0.0727 (16)	0.0363 (12)	−0.0164 (13)	−0.0167 (11)	−0.0086 (11)
C3	0.0580 (14)	0.0666 (15)	0.0427 (13)	−0.0117 (12)	−0.0069 (11)	−0.0049 (12)
C4	0.0421 (12)	0.0782 (16)	0.0521 (15)	−0.0057 (11)	−0.0173 (11)	0.0003 (12)
C5	0.0693 (15)	0.0441 (12)	0.0515 (14)	−0.0153 (11)	−0.0271 (12)	−0.0008 (10)
C6	0.0758 (16)	0.0650 (14)	0.0508 (15)	−0.0256 (13)	−0.0228 (12)	−0.0137 (12)
C7	0.0502 (12)	0.0509 (12)	0.0394 (12)	−0.0091 (10)	−0.0103 (9)	−0.0097 (10)
C8	0.0562 (12)	0.0474 (12)	0.0385 (12)	−0.0122 (10)	−0.0172 (10)	−0.0080 (9)
C9	0.0569 (14)	0.0536 (12)	0.0395 (12)	−0.0016 (10)	−0.0201 (10)	−0.0010 (10)
C10	0.0627 (13)	0.0500 (12)	0.0312 (11)	−0.0271 (10)	−0.0145 (10)	0.0016 (9)
C11	0.0499 (12)	0.0434 (11)	0.0393 (12)	−0.0156 (9)	−0.0046 (9)	−0.0049 (9)
C12	0.0454 (11)	0.0378 (10)	0.0363 (11)	−0.0049 (8)	−0.0156 (9)	−0.0067 (8)
C13	0.0395 (10)	0.0442 (11)	0.0357 (11)	−0.0132 (8)	−0.0114 (9)	0.0045 (9)
C14	0.0487 (12)	0.0385 (10)	0.0361 (11)	−0.0070 (9)	−0.0142 (9)	0.0012 (8)
C15	0.0423 (11)	0.0369 (10)	0.0390 (11)	−0.0141 (8)	−0.0114 (9)	−0.0004 (8)
C16	0.0450 (11)	0.0460 (11)	0.0325 (10)	−0.0157 (9)	−0.0140 (9)	−0.0017 (8)
C17	0.0537 (12)	0.0446 (11)	0.0379 (11)	−0.0208 (10)	−0.0214 (10)	0.0070 (9)
C18	0.0429 (11)	0.0400 (10)	0.0395 (11)	−0.0049 (8)	−0.0158 (9)	−0.0060 (9)

Geometric parameters (Å, º) top

Cl1—C12	1.735 (2)	C1—C5	1.371 (4)
Cl2—C7	1.728 (2)	C1—H1B	0.9300
Cl3—C5	1.729 (3)	C2—C7	1.367 (3)
O1—C18	1.360 (2)	C2—H2B	0.9300
O1—C13	1.402 (2)	C3—C14	1.390 (3)
O2—C8	1.351 (3)	C3—H3B	0.9300
O2—C10	1.411 (3)	C4—C18	1.386 (3)
O3—C14	1.357 (3)	C4—H4B	0.9300
O3—C15	1.396 (2)	C6—C8	1.394 (3)
N1—C3	1.317 (3)	C6—H6B	0.9300
N1—C1	1.323 (4)	C9—C12	1.364 (3)
N2—C4	1.319 (3)	C9—H9A	0.9300
N2—C9	1.330 (3)	C10—C17	1.369 (3)
N3—C2	1.326 (3)	C10—C11	1.377 (3)
N3—C6	1.326 (3)	C11—C13	1.374 (3)
N4—C14	1.312 (3)	C11—H11A	0.9300
N4—C5	1.320 (3)	C13—C16	1.377 (3)
N5—C8	1.312 (3)	C15—C17	1.379 (3)
N5—C7	1.325 (3)	C15—C16	1.382 (3)
N6—C18	1.310 (3)	C16—H16A	0.9300
N6—C12	1.328 (2)	C17—H17A	0.9300

C18—O1—C13	118.64 (15)	O2—C8—C6	116.6 (2)
C8—O2—C10	118.93 (16)	N2—C9—C12	119.8 (2)
C14—O3—C15	121.38 (16)	N2—C9—H9A	120.1
C3—N1—C1	117.2 (2)	C12—C9—H9A	120.1
C4—N2—C9	117.46 (19)	C17—C10—C11	122.6 (2)
C2—N3—C6	116.8 (2)	C17—C10—O2	119.58 (19)
C14—N4—C5	115.09 (19)	C11—C10—O2	117.48 (19)
C8—N5—C7	114.59 (18)	C13—C11—C10	117.54 (19)
C18—N6—C12	114.85 (16)	C13—C11—H11A	121.2
N1—C1—C5	120.6 (2)	C10—C11—H11A	121.2
N1—C1—H1B	119.7	N6—C12—C9	124.2 (2)
C5—C1—H1B	119.7	N6—C12—Cl1	116.16 (14)
N3—C2—C7	120.9 (2)	C9—C12—Cl1	119.64 (17)
N3—C2—H2B	119.6	C11—C13—C16	122.78 (18)
C7—C2—H2B	119.6	C11—C13—O1	117.27 (18)
N1—C3—C14	120.9 (2)	C16—C13—O1	119.85 (19)
N1—C3—H3B	119.6	N4—C14—O3	120.43 (19)
C14—C3—H3B	119.6	N4—C14—C3	122.7 (2)
N2—C4—C18	121.0 (2)	O3—C14—C3	116.8 (2)
N2—C4—H4B	119.5	C17—C15—C16	122.55 (19)
C18—C4—H4B	119.5	C17—C15—O3	115.06 (17)
N4—C5—C1	123.6 (2)	C16—C15—O3	121.97 (19)
N4—C5—Cl3	116.79 (18)	C13—C16—C15	116.97 (19)
C1—C5—Cl3	119.6 (2)	C13—C16—H16A	121.5
N3—C6—C8	120.7 (2)	C15—C16—H16A	121.5
N3—C6—H6B	119.6	C10—C17—C15	117.57 (19)
C8—C6—H6B	119.6	C10—C17—H17A	121.2
N5—C7—C2	124.0 (2)	C15—C17—H17A	121.2
N5—C7—Cl2	116.06 (17)	N6—C18—O1	120.19 (17)
C2—C7—Cl2	119.97 (18)	N6—C18—C4	122.7 (2)
N5—C8—O2	120.29 (18)	O1—C18—C4	117.13 (19)
N5—C8—C6	123.1 (2)

C3—N1—C1—C5	−0.2 (4)	N2—C9—C12—Cl1	179.78 (19)
C6—N3—C2—C7	0.5 (4)	C10—C11—C13—C16	1.0 (3)
C1—N1—C3—C14	−0.4 (4)	C10—C11—C13—O1	−175.44 (17)
C9—N2—C4—C18	−0.6 (4)	C18—O1—C13—C11	−111.4 (2)
C14—N4—C5—C1	−0.4 (3)	C18—O1—C13—C16	72.1 (2)
C14—N4—C5—Cl3	−178.98 (14)	C5—N4—C14—O3	175.50 (17)
N1—C1—C5—N4	0.7 (4)	C5—N4—C14—C3	−0.2 (3)
N1—C1—C5—Cl3	179.2 (2)	C15—O3—C14—N4	33.3 (3)
C2—N3—C6—C8	−0.4 (4)	C15—O3—C14—C3	−150.69 (19)
C8—N5—C7—C2	−1.0 (3)	N1—C3—C14—N4	0.7 (3)
C8—N5—C7—Cl2	178.31 (15)	N1—C3—C14—O3	−175.2 (2)
N3—C2—C7—N5	0.2 (4)	C14—O3—C15—C17	−150.15 (18)
N3—C2—C7—Cl2	−179.10 (19)	C14—O3—C15—C16	37.0 (3)
C7—N5—C8—O2	−179.47 (19)	C11—C13—C16—C15	−0.8 (3)
C7—N5—C8—C6	1.1 (3)	O1—C13—C16—C15	175.49 (16)
C10—O2—C8—N5	8.9 (3)	C17—C15—C16—C13	−0.1 (3)
C10—O2—C8—C6	−171.7 (2)	O3—C15—C16—C13	172.23 (17)
N3—C6—C8—N5	−0.5 (4)	C11—C10—C17—C15	−0.6 (3)
N3—C6—C8—O2	−179.9 (2)	O2—C10—C17—C15	172.20 (17)
C4—N2—C9—C12	1.0 (4)	C16—C15—C17—C10	0.8 (3)
C8—O2—C10—C17	76.1 (3)	O3—C15—C17—C10	−172.01 (17)
C8—O2—C10—C11	−110.8 (2)	C12—N6—C18—O1	179.91 (17)
C17—C10—C11—C13	−0.2 (3)	C12—N6—C18—C4	1.8 (3)
O2—C10—C11—C13	−173.20 (17)	C13—O1—C18—N6	4.8 (3)
C18—N6—C12—C9	−1.4 (3)	C13—O1—C18—C4	−177.0 (2)
C18—N6—C12—Cl1	178.83 (14)	N2—C4—C18—N6	−0.9 (4)
N2—C9—C12—N6	0.0 (3)	N2—C4—C18—O1	−179.0 (2)

Experimental details

Crystal data
Chemical formula	C₁₈H₉Cl₃N₆O₃
M_r	463.66
Crystal system, space group	Triclinic, P1
Temperature (K)	298
a, b, c (Å)	9.680 (2), 10.658 (2), 11.039 (3)
α, β, γ (°)	72.768 (3), 68.308 (3), 69.342 (3)
V (Å³)	972.0 (4)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.51
Crystal size (mm)	0.58 × 0.31 × 0.30

Data collection
Diffractometer	Bruker SMART CCD area-detector
Absorption correction	Multi-scan (SADABS; Sheldrick, 2004)
T_min, T_max	0.758, 0.863
No. of measured, independent and observed [I > 2σ(I)] reflections	4925, 3375, 2797
R_int	0.017
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.041, 0.108, 1.04
No. of reflections	3375
No. of parameters	271
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.22, −0.39

Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2001), SHELXTL (Sheldrick, 2001), SHELXTL and local programs.

References

Bruker (2001). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Carter, D. R. & Boer, F. P. (1974). J. Chem. Soc. Perkin Trans. 2, pp. 1841–1844. CrossRef Google Scholar
Seitz, L. E., Suling, W. J. & Reynolds, R. C. (2002). J. Med. Chem. 45, 5604–5606. Web of Science CrossRef PubMed CAS Google Scholar
Sheldrick, G. M. (2001). SHELXTL. Version 5.0. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Sheldrick, G. M. (2004). SADABS. University of Göttingen, Germany. Google Scholar
Temple, C. Jr, Rose, J. D. & Montgomery, J. A. (1970). J. Med. Chem. 13, 1234–1235. CrossRef CAS PubMed Web of Science Google Scholar