3-[1-(4-Methyl­phen­ylsulfon­yl)-1,4-di­hydro­pyridin-4-yl]-1H-indole

Oliveira-Campos, A.M.F.; Ribeiro, J.M.O.; Rodrigues, L.M.; Parpot, P.; Lopes, P.E.

doi:10.1107/S1600536810010214

organic compounds

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ISSN: 2056-9890

Volume 66| Part 4| April 2010| Page o915

doi:10.1107/S1600536810010214

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3-[1-(4-Methylphenylsulfonyl)-1,4-dihydropyridin-4-yl]-1H-indole

Ana M. F. Oliveira-Campos,^a Joana M. O. Ribeiro,^a Lígia M. Rodrigues,^a Pier Parpot ^a and Paulo E. Lopes ^a ^*

^aCentro de Química, Universidade do Minho, Campus de Gualtar, 4710-452 Braga, Portugal
^*Correspondence e-mail: pelopes@netc.pt

(Received 11 March 2010; accepted 18 March 2010; online 24 March 2010)

In the title compound, C₂₀H₁₈N₂O₂S, the indole mean plane and benzene ring form a dihedral angle of 65.0 (1)°. In the crystal structure, weak intermolecular N—H⋯π and C—H⋯O interactions link the molecules into ribbons propagated along [100].

Related literature

For the pharmacological activity of compounds containing indole and pyridine fragments, see: Fanshawe et al. (1970 ); Bennasar et al. (1990 ); Lavilla et al. (1997 ).

Experimental

Crystal data

C₂₀H₁₈N₂O₂S
M_r = 350.42
Orthorhombic, P 2₁ 2₁ 2₁
a = 7.9192 (9) Å
b = 11.4344 (13) Å
c = 19.168 (2) Å
V = 1735.7 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.20 mm⁻¹
T = 293 K
0.47 × 0.45 × 0.42 mm

Data collection

Bruker SMART 1000 CCD diffractometer
11335 measured reflections
4115 independent reflections
2830 reflections with I > 2σ(I)
R_int = 0.036

Refinement

R[F² > 2σ(F²)] = 0.041
wR(F²) = 0.102
S = 1.01
4115 reflections
231 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.17 e Å⁻³
Δρ_min = −0.24 e Å⁻³
Absolute structure: Flack (1983 ), 1718 Friedel pairs
Flack parameter: −0.07 (8)

Table 1
Hydrogen-bond geometry (Å, °)

Cg is the centroid of the C1–C6 ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C10—H10⋯O1ⁱ	0.93	2.54	3.370 (3)	149
N1—H1⋯Cgⁱⁱ	0.83 (3)	2.51	3.207 (3)	143
Symmetry codes: (i) x-1, y, z; (ii) $[x-{\script{1\over 2}}, -y-{\script{1\over 2}}, -z]$ .

Data collection: SMART (Bruker 2001 ); cell refinement: SAINT (Bruker 2001); data reduction: SAINT; 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 and publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810010214/cv2703sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536810010214/cv2703Isup2.hkl

checkCIF report

Comment top

A vast number of compounds containing both indole and pyridine fragments exhibit pharmacological activity (Fanshawe et al. 1970, Lavilla et al. 1997). Attempted N-tosylation of indole in pyridine gave a product which did not correspond to the expected N-tosylindole. Crystallization of this compound from acetonitrile yielded light pink crystals of a compound that by ESI-MS, ¹H and ¹³C NMR data showed to contain indole, dihydropyridine and the tosyl group. Following studies on the nucleophilic addition of indole to pyridinium salts (Bennasar et al., 1990; Lavilla et al. 1997) the structure for the isolated compound was suggested to be 3-{1-[(4-Methylphenyl)sulfonil]-1,4-dihydropyridin-4-yl}-1H- indole (Scheme 1) and later confirmed by single-crystal X-ray diffraction (Figure 1).

Related literature top

For the pharmacological activity of compounds containing indole and pyridine fragments, see: Fanshawe et al. (1970); Bennasar et al. (1990); Lavilla et al. 1997).

Experimental top

To a solution of indole (5.0 g; 4.3x10^-2 mol) in pyridine (10 mL) tosyl chloride (5.4 g; 2.8x10^-2 mol) was added at 0°C. The mixture was left stirring for 90 minutes, at room temperature, then HCl (10%) was added dropwise until neutral and the mixture was extracted with chloroform (4x20 ml). The organic extracts were combined, dried (MgSO₄), and evaporated to dryness to give an oily orange solid (3.1 g, η=20%). Crystallization from acetonitrile gave light pink crystals (0.9 g), m.p. 147.8-150.7°C of 3-{1-[(4-Methylphenyl)sulfonil]-1,4-dihydropyridin-4-yl}-1H-indole.

¹H NMR, (DMSO-d₆, 300 MHz): δ 10.84 (s, 1H, NH), 7.78 (d, 2H, J = 8.1 Hz, H-2" and H-6"), 7.49 (d, 2H, J = 8.1 Hz, H-3" and H-5"), 7.29 (d, 1H, J=7.8 Hz, H-4), 7.14 (d, 1H, J=7.8 Hz, H-7), 7.01 (t, 1H, J=7.5 Hz, H-6), 6.85 (d, 1H, J=2.4 Hz, H-2), 6.72 (t, 1H, J=7.8, H-5), 6.61 (dd, 2H, J=1,5 e 8.1 Hz, H-2' e H-6'), 5.02 (dd, 2H, J=2.4 e 8.7 Hz, H-3' e H-5'), 4.27 (m, 1H, H-4'), 2.46 (s, 3H, CH₃). ¹³C NMR (DMSO-d₆): δ 144.53 (C-4"), 136.60 (C-7a), 134.31 (C-1"), 130.20 (C-3" and C-5"), 126.87 (C-2" and C-6"), 125.78 (C-3a), 122.26 (C-2), 121.06 (C-2' and C-6'), 120.93 (C-6), 118.46 (C-7), 118.21 (C-5 or C-1), 118.16 (C-5 or C-1), 111.71 (C-3' and C-5'), 111.48 (C-4), 29.17 (C-4'), 21.12 (CH₃). ESI- MS: The molecular ion was not observed, only the ion at 195 (M-155)⁺ corresponding to the loss of tosyl from the molecular ion.

Computing details top

Data collection: SMART (Bruker 2001); cell refinement: SAINT (Bruker 2001); data reduction: SAINT (Bruker 2001); 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) and publCIF (Westrip, 2010).

Figures top

Fig. 1. The molecular structure of the title compound showing the atomic numbering and 50 % probability displacement ellipsoids.

3-[1-(4-Methylphenylsulfonyl)-1,4-dihydropyridin-4-yl]-1H-indole top

Crystal data top

C₂₀H₁₈N₂O₂S	F(000) = 736
M_r = 350.42	D_x = 1.341 Mg m⁻³
Orthorhombic, P2₁2₁2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 2827 reflections
a = 7.9192 (9) Å	θ = 2.6–21.5°
b = 11.4344 (13) Å	µ = 0.20 mm⁻¹
c = 19.168 (2) Å	T = 293 K
V = 1735.7 (3) Å³	Prism, light pink
Z = 4	0.47 × 0.45 × 0.42 mm

Data collection top

Bruker SMART 1000 CCD diffractometer	2830 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.036
Graphite monochromator	θ_max = 28.0°, θ_min = 2.1°
phi and ω scans	h = −10→10
11335 measured reflections	k = −10→14
4115 independent reflections	l = −25→22

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.041	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.102	w = 1/[σ²(F_o²) + (0.0423P)² + 0.2268P] where P = (F_o² + 2F_c²)/3
S = 1.01	(Δ/σ)_max < 0.001
4115 reflections	Δρ_max = 0.17 e Å⁻³
231 parameters	Δρ_min = −0.24 e Å⁻³
0 restraints	Absolute structure: Flack (1983), 1718 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −0.07 (8)

Crystal data top

C₂₀H₁₈N₂O₂S	V = 1735.7 (3) Å³
M_r = 350.42	Z = 4
Orthorhombic, P2₁2₁2₁	Mo Kα radiation
a = 7.9192 (9) Å	µ = 0.20 mm⁻¹
b = 11.4344 (13) Å	T = 293 K
c = 19.168 (2) Å	0.47 × 0.45 × 0.42 mm

Data collection top

Bruker SMART 1000 CCD diffractometer	2830 reflections with I > 2σ(I)
11335 measured reflections	R_int = 0.036
4115 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.041	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.102	Δρ_max = 0.17 e Å⁻³
S = 1.01	Δρ_min = −0.24 e Å⁻³
4115 reflections	Absolute structure: Flack (1983), 1718 Friedel pairs
231 parameters	Absolute structure parameter: −0.07 (8)
0 restraints

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 > 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
S	0.43816 (8)	0.16555 (6)	0.18936 (3)	0.05332 (19)
O1	0.5841 (2)	0.12035 (19)	0.22313 (9)	0.0705 (6)
O2	0.3845 (3)	0.28318 (17)	0.20181 (9)	0.0720 (6)
N1	−0.1929 (3)	−0.2711 (2)	0.05481 (12)	0.0609 (7)
H1	−0.249 (4)	−0.330 (3)	0.0446 (15)	0.078 (10)*
C1	−0.1217 (3)	−0.1920 (2)	0.01063 (12)	0.0458 (6)
C2	−0.1307 (3)	−0.1842 (3)	−0.06159 (12)	0.0561 (7)
H2	−0.1872	−0.2404	−0.0877	0.067*
C3	−0.0535 (4)	−0.0909 (2)	−0.09299 (12)	0.0592 (7)
H3	−0.0601	−0.0825	−0.1412	0.071*
C4	0.0354 (3)	−0.0080 (2)	−0.05365 (12)	0.0529 (6)
H4	0.0885	0.0538	−0.0764	0.063*
C5	0.0459 (3)	−0.01583 (19)	0.01780 (11)	0.0440 (5)
H5	0.1060	0.0396	0.0432	0.053*
C6	−0.0352 (3)	−0.10865 (18)	0.05181 (11)	0.0366 (5)
C7	−0.0614 (3)	−0.14245 (19)	0.12343 (10)	0.0415 (5)
C8	−0.1592 (3)	−0.2394 (2)	0.12171 (12)	0.0548 (7)
H8	−0.1982	−0.2789	0.1609	0.066*
C9	0.0027 (3)	−0.0848 (2)	0.18946 (11)	0.0444 (6)
H9	−0.0680	−0.1132	0.2279	0.053*
C10	−0.0131 (3)	0.0452 (2)	0.18840 (12)	0.0463 (6)
H10	−0.1194	0.0769	0.1802	0.056*
C11	0.1134 (3)	0.1181 (2)	0.19833 (11)	0.0459 (6)
H11	0.0928	0.1979	0.1949	0.055*
N2	0.2792 (2)	0.08014 (18)	0.21399 (9)	0.0445 (5)
C13	0.3048 (3)	−0.0418 (2)	0.21675 (11)	0.0473 (6)
H13	0.4128	−0.0697	0.2260	0.057*
C12	0.1825 (3)	−0.1175 (2)	0.20673 (10)	0.0462 (6)
H12	0.2084	−0.1966	0.2105	0.055*
C14	0.4588 (3)	0.1429 (2)	0.09933 (11)	0.0456 (6)
C15	0.5422 (3)	0.0451 (2)	0.07507 (12)	0.0542 (6)
H15	0.5929	−0.0064	0.1063	0.065*
C16	0.5499 (3)	0.0241 (2)	0.00439 (13)	0.0595 (7)
H16	0.6064	−0.0419	−0.0117	0.071*
C17	0.4753 (4)	0.0990 (3)	−0.04315 (12)	0.0563 (7)
C18	0.3938 (4)	0.1972 (2)	−0.01774 (13)	0.0611 (7)
H18	0.3451	0.2493	−0.0490	0.073*
C19	0.3829 (3)	0.2198 (2)	0.05302 (13)	0.0549 (7)
H19	0.3257	0.2854	0.0692	0.066*
C20	0.4842 (5)	0.0734 (3)	−0.12010 (14)	0.0867 (11)
H20A	0.4108	0.1259	−0.1448	0.130*
H20B	0.4494	−0.0058	−0.1285	0.130*
H20C	0.5981	0.0838	−0.1361	0.130*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S	0.0401 (3)	0.0752 (5)	0.0447 (3)	−0.0101 (3)	−0.0001 (3)	−0.0173 (3)
O1	0.0388 (10)	0.1244 (18)	0.0481 (9)	−0.0081 (11)	−0.0087 (8)	−0.0082 (10)
O2	0.0725 (13)	0.0654 (12)	0.0783 (13)	−0.0150 (10)	0.0113 (10)	−0.0355 (10)
N1	0.0710 (17)	0.0531 (14)	0.0587 (14)	−0.0285 (13)	−0.0069 (11)	−0.0050 (12)
C1	0.0458 (13)	0.0460 (14)	0.0457 (12)	0.0012 (12)	−0.0048 (10)	−0.0067 (11)
C2	0.0607 (15)	0.0638 (18)	0.0438 (13)	0.0057 (14)	−0.0102 (12)	−0.0176 (13)
C3	0.0673 (18)	0.0776 (19)	0.0328 (12)	0.0201 (17)	−0.0006 (13)	0.0021 (12)
C4	0.0640 (17)	0.0497 (14)	0.0451 (13)	0.0098 (13)	0.0084 (12)	0.0085 (12)
C5	0.0489 (14)	0.0384 (12)	0.0446 (12)	−0.0006 (12)	0.0027 (11)	−0.0016 (10)
C6	0.0359 (13)	0.0353 (11)	0.0384 (11)	0.0033 (10)	−0.0015 (9)	−0.0017 (9)
C7	0.0428 (12)	0.0451 (13)	0.0366 (11)	−0.0043 (11)	−0.0039 (10)	0.0020 (9)
C8	0.0609 (17)	0.0559 (17)	0.0475 (14)	−0.0164 (13)	−0.0008 (12)	0.0081 (12)
C9	0.0428 (12)	0.0585 (15)	0.0318 (11)	−0.0053 (11)	0.0023 (10)	−0.0024 (11)
C10	0.0342 (11)	0.0581 (15)	0.0465 (12)	0.0069 (11)	−0.0015 (10)	−0.0145 (12)
C11	0.0410 (12)	0.0518 (14)	0.0450 (13)	0.0097 (11)	−0.0029 (10)	−0.0137 (11)
N2	0.0351 (10)	0.0594 (14)	0.0391 (10)	0.0019 (9)	−0.0016 (8)	−0.0063 (9)
C13	0.0421 (13)	0.0651 (18)	0.0346 (11)	0.0115 (13)	−0.0017 (10)	−0.0013 (11)
C12	0.0553 (15)	0.0525 (15)	0.0309 (11)	0.0059 (13)	−0.0031 (10)	0.0011 (10)
C14	0.0373 (13)	0.0566 (15)	0.0429 (12)	−0.0058 (12)	0.0018 (10)	−0.0064 (11)
C15	0.0490 (15)	0.0706 (18)	0.0429 (13)	0.0124 (14)	−0.0001 (12)	0.0012 (12)
C16	0.0561 (16)	0.0716 (18)	0.0509 (14)	0.0103 (15)	0.0084 (13)	−0.0096 (13)
C17	0.0550 (17)	0.0714 (18)	0.0424 (13)	−0.0195 (14)	0.0036 (12)	0.0032 (12)
C18	0.0675 (18)	0.0613 (18)	0.0544 (15)	−0.0117 (15)	−0.0071 (13)	0.0167 (14)
C19	0.0552 (16)	0.0484 (14)	0.0611 (16)	−0.0029 (13)	0.0023 (13)	−0.0008 (13)
C20	0.103 (3)	0.114 (3)	0.0430 (15)	−0.029 (2)	0.0031 (16)	0.0028 (16)

Geometric parameters (Å, º) top

S—O1	1.4217 (19)	C15—C16	1.377 (3)
S—O2	1.431 (2)	C16—C17	1.383 (4)
S—N2	1.662 (2)	C17—C18	1.383 (4)
S—C14	1.753 (2)	C17—C20	1.505 (4)
N1—C8	1.359 (3)	C18—C19	1.383 (3)
N1—C1	1.361 (3)	N1—H1	0.83 (3)
C1—C2	1.389 (3)	C2—H2	0.93
C1—C6	1.415 (3)	H3—C3	0.93
C2—C3	1.369 (4)	C4—H4	0.93
C3—C4	1.401 (4)	C5—H5	0.93
C4—C5	1.375 (3)	C8—H8	0.93
C5—C6	1.401 (3)	H9—C9	0.98
C6—C7	1.441 (3)	C10—H10	0.93
C7—C8	1.353 (3)	C11—H11	0.93
C7—C9	1.514 (3)	C12—H12	0.93
C9—C10	1.492 (3)	C13—H13	0.93
C9—C12	1.509 (3)	C15—H15	0.93
C10—C11	1.316 (3)	C16—H16	0.93
C11—N2	1.415 (3)	C18—H18	0.93
N2—C13	1.410 (3)	C19—H19	0.93
C13—C12	1.314 (3)	C20—H20A	0.96
C14—C15	1.379 (3)	C20—H20B	0.96
C14—C19	1.386 (3)	C20—H20C	0.96

O1—S—O2	120.47 (12)	C18—C17—C20	121.6 (3)
O1—S—N2	105.83 (11)	C19—C18—C17	121.7 (3)
O2—S—N2	106.28 (11)	C18—C19—C14	118.8 (2)
O1—S—C14	108.58 (11)	C1—N1—H1	128 (2)
O2—S—C14	109.32 (12)	C8—N1—H1	123 (2)
N2—S—C14	105.29 (10)	N1—C8—H8	124.6
C8—N1—C1	109.2 (2)	C7—C8—H8	124.7
N1—C1—C2	130.0 (2)	C1—C2—H2	121.1
N1—C1—C6	107.5 (2)	C3—C2—H2	121.1
C2—C1—C6	122.5 (2)	C2—C3—H3	119.5
C3—C2—C1	117.8 (2)	C4—C3—H3	119.5
C2—C3—C4	121.0 (2)	C3—C4—H4	119.2
C5—C4—C3	121.5 (2)	C5—C4—H4	119.3
C4—C5—C6	119.0 (2)	C4—C5—H5	120.5
C5—C6—C1	118.2 (2)	C6—C5—H5	120.5
C5—C6—C7	135.4 (2)	C7—C9—H9	107
C1—C6—C7	106.32 (19)	C12—C9—H9	107
C8—C7—C6	106.19 (19)	C10—C9—H9	107
C8—C7—C9	124.7 (2)	C9—C10—H10	117.8
C6—C7—C9	129.1 (2)	C11—C10—H10	117.8
C7—C8—N1	110.7 (2)	C10—C11—H11	118.5
C10—C9—C12	109.2 (2)	N2—C11—H11	118.6
C10—C9—C7	113.21 (19)	C9—C12—H12	117.8
C12—C9—C7	113.0 (2)	C13—C12—H12	117.8
C11—C10—C9	124.4 (2)	C12—C13—H13	118.7
C10—C11—N2	122.9 (2)	N2—C13—H13	118.6
C13—N2—C11	116.4 (2)	C14—C15—H15	120.2
C13—N2—S	118.87 (16)	C16—C15—H15	120.2
C11—N2—S	117.57 (17)	C15—C16—H16	119.3
C12—C13—N2	122.7 (2)	C17—C16—H16	119.3
C13—C12—C9	124.4 (2)	C17—C18—H18	119.1
C15—C14—C19	120.4 (2)	C19—C18—H18	119.1
C15—C14—S	119.76 (18)	C18—C19—H19	120.5
C19—C14—S	119.75 (19)	C14—C19—H19	120.6
C16—C15—C14	119.6 (2)	C17—C20—H20A	109.5
C15—C16—C17	121.4 (2)	C17—C20—H20C	109.4
C16—C17—C18	118.0 (2)	C17—C20—H20B	109.5
C16—C17—C20	120.4 (3)	H20A—C20—H20C	109.5

Hydrogen-bond geometry (Å, º) top

Cg is the centroid of the C1–C6 ring.

D—H···A	D—H	H···A	D···A	D—H···A
C10—H10···O1ⁱ	0.93	2.54	3.370 (3)	149
N1—H1···Cgⁱⁱ	0.83 (3)	2.51	3.207 (3)	143

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

Experimental details

Crystal data
Chemical formula	C₂₀H₁₈N₂O₂S
M_r	350.42
Crystal system, space group	Orthorhombic, P2₁2₁2₁
Temperature (K)	293
a, b, c (Å)	7.9192 (9), 11.4344 (13), 19.168 (2)
V (Å³)	1735.7 (3)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.20
Crystal size (mm)	0.47 × 0.45 × 0.42

Data collection
Diffractometer	Bruker SMART 1000 CCD diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	11335, 4115, 2830
R_int	0.036
(sin θ/λ)_max (Å⁻¹)	0.660

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.041, 0.102, 1.01
No. of reflections	4115
No. of parameters	231
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.17, −0.24
Absolute structure	Flack (1983), 1718 Friedel pairs
Absolute structure parameter	−0.07 (8)

Computer programs: SMART (Bruker 2001), SAINT (Bruker 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008) and publCIF (Westrip, 2010).

Hydrogen-bond geometry (Å, º) top

Cg is the centroid of the C1–C6 ring.

D—H···A	D—H	H···A	D···A	D—H···A
C10—H10···O1ⁱ	0.93	2.54	3.370 (3)	149
N1—H1···Cgⁱⁱ	0.83 (3)	2.51	3.207 (3)	143

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

Acknowledgements

The authors are pleased to thank the Fundação para a Ciência e a Tecnologia (FCT) (grant POCTI-SFA-3-686), FEDER (Portugal) and REEQ/ 630/QUI/2005 for financial support.

References

Bennasar, M.-L., Alvarez, M., Lavilla, R., Zulaica, E. & Bosch, J. (1990). J. Org. Chem. 55, 1156–1168. CrossRef CAS Web of Science Google Scholar
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Volume 66| Part 4| April 2010| Page o915

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