organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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meso-4,5-Di­phenyl­imidazolidin-2-one

aDepartment of Chemistry and Biology, Ryerson University, Toronto, Ontario, Canada M5B 2K3, and bDepartment of Chemistry, University of Toronto, 80 St George St, Toronto, Ontario, Canada M5B 2K3
*Correspondence e-mail: alough@chem.utoronto.ca

(Received 29 October 2009; accepted 2 November 2009; online 14 November 2009)

The crystal structure determination of the title compound, C15H14N2O, confirms the cis relationship between the phenyl groups at the 4- and 5-positions on the imidazolidine ring. The dihedral angle between the two phenyl rings is 48.14 (6)°. In the crystal structure, inter­molecular N—H⋯O hydrogen bonds link mol­ecules into centrosymmetric dimers. These dimers are, in turn, linked into a two-dimensional network via weak N—H⋯π(arene) inter­actions and ππ stacking inter­actions with centroid–centroid distances of 3.6937 (11) Å.

Related literature

For the first synthesis of this compound, see: Biniecki & Moll (1974[Biniecki, S. & Moll, M. (1974). Acta Pol. Pharm. 31, 731-734.]). For the synthesis of the trans-isomers, see: Sankhavasi et al. (1991[Sankhavasi, W., Yamamoto, M., Kohmoto, S. & Yamada, K. (1991). Bull. Chem. Soc. Jpn, 64, 1425-1427.]). For the crystal structure of the (R,R)-isomer, see: Siegler & Long (2006[Siegler, M. & Long, S. (2006). Acta Cryst. E62, o5310-o5311.]). For the synthesis of the precursor, see: Proskurnina et al. (2002[Proskurnina, M. V., Lozinskaya, N. A., Tkachenko, S. E. & Zefirov, N. S. (2002). Russ. J. Org. Chem. 8, 1149-1153.]). For applications of related enanti­opure compounds, see: Sankhavasi et al. (1991[Sankhavasi, W., Yamamoto, M., Kohmoto, S. & Yamada, K. (1991). Bull. Chem. Soc. Jpn, 64, 1425-1427.]); Isobe et al. (1998[Isobe, T., Fukuda, K. & Ishikawa, T. (1998). Tetrahedron Asymmetry, 9, 1729-1735.]); Lou et al. (2004[Lou, Y., Horikawa, M., Kloster, R. A., Hawryluk, N. A. & Corey, E. J. (2004). J. Am. Chem. Soc. 126, 8916-8918.]). For potential applications of the title compound, see: Porosa & Viirre (2009[Porosa, L. & Viirre, R. D. (2009). Tetrahedron Lett. 50, 4170-4173.]).

[Scheme 1]

Experimental

Crystal data
  • C15H14N2O

  • Mr = 238.28

  • Triclinic, [P \overline 1]

  • a = 6.3539 (4) Å

  • b = 8.6159 (4) Å

  • c = 11.3211 (7) Å

  • α = 86.147 (3)°

  • β = 76.094 (3)°

  • γ = 82.718 (3)°

  • V = 596.32 (6) Å3

  • Z = 2

  • Mo Kα radiation

  • μ = 0.09 mm−1

  • T = 150 K

  • 0.20 × 0.20 × 0.08 mm

Data collection
  • Nonius KappaCCD diffractometer

  • Absorption correction: multi-scan (SORTAV; Blessing, 1995[Blessing, R. H. (1995). Acta Cryst. A51, 33-38.]) Tmin = 0.873, Tmax = 0.995

  • 6535 measured reflections

  • 2685 independent reflections

  • 1771 reflections with I > 2σ(I)

  • Rint = 0.047

Refinement
  • R[F2 > 2σ(F2)] = 0.054

  • wR(F2) = 0.156

  • S = 1.03

  • 2685 reflections

  • 172 parameters

  • H atoms treated by a mixture of independent and constrained refinement

  • Δρmax = 0.25 e Å−3

  • Δρmin = −0.25 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N1—H1N⋯O1i 0.93 (2) 1.94 (2) 2.864 (2) 173 (2)
N2—H2NCg1ii 0.87 (2) 2.46 (2) 3.322 (2) 165 (2)
Symmetry codes: (i) -x+1, -y+1, -z+1; (ii) -x, -y+1, -z+2. Cg1 is the centroid of the C4–C9 ring.

Data collection: COLLECT (Nonius, 2002[Nonius (2002). COLLECT. Nonius BV, Delft, The Netherlands.]); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]); data reduction: DENZO-SMN; program(s) used to solve structure: SIR92 (Altomare et al., 1994[Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994). J. Appl. Cryst. 27, 435.]); program(s) used to refine structure: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]); software used to prepare material for publication: SHELXTL.

Supporting information


Comment top

The title compound is a meso-compound, and is therefore achiral. The trans-isomer is chiral, and both antipodal isomers have been synthesized (Sankhavasi et al., 1991). The crystal structure of the (4R,5R)-isomer has already been determined (Siegler & Long, 2006). Enantiopure samples of the trans-isomers have found use as precursors for chiral auxiliaries (Sankhavasi et al., 1991), chiral catalysts (Isobe et al., 1998), and chiral ligands (Lou et al., 2004). The title compound might also be of similar use if desymmetrization can be accomplished by selective reaction of one of the two enantiotopic nitrogen atoms, for instance using an enantioselective Buchwald-Hartwig reaction (Porosa & Viirre (2009).

The title compound was prepared according to the reaction scheme shown in Fig. 3. The imine-amide precursor is readily prepared by heating benzaldehyde with NH4OAc according to a literature procedure (Proskurnina et al., 2002). This compound was subjected to exhaustive hydrolysis, by heating in a mixture of HBr and acetic acid for four days, and the resultant meso-diamine was then treated with carbonyl diimidazole, resulting in the title compound.

The molecular structure is shown in Fig. 1 and confirms the cis-relationship between the phenyl groups at the 4 and 5 positions (atoms C1 and C3 by the crystallographic labelling scheme). This relative stereochemistry is initially set in the formation of the imine-amide species, which involves an electrocyclization governed by orbital symmetry considerations. Epimerization did not occur, even upon prolonged exposure to strong acid and heat in the hydrolysis of the imine and amide groups.

The dihedral angle between the two phenyl rings (C4—C9 and C10—C15) is 48.14 (6)°. In the crystal structure, intermolecular N—H···O hydrogen bonds link molecules into centrostmmetric dimers (Fig. 2). These dimers, are in turn, linked into a two-dimensional network via weak N—H···π(arene) interactions and ππ stacking interactions with Cg1···Cg1(-x, 2 - y, 1 - z) = 3.6937 (11) Å, where Cg1 is the centroid defined by ring atoms C4—C9.

Related literature top

For the first synthesis of this compound, see: Biniecki & Moll (1974). For the synthesis of the trans-isomers, see: Sankhavasi et al. (1991). For the crystal structure of the (R,R)-isomer, see: Siegler & Long (2006). For the synthesis of the precursor, see: Proskurnina et al. (2002). For applications of related enantiopure compounds, see: Sankhavasi et al. (1991); Isobe et al. (1998); Lou et al. (2004). For potential applications of the title compound, see: Porosa & Viirre (2009). Cg1 is the centroid of the C4–C9 ring.

Experimental top

A suspension of 1,2-diamino-N-benzoyl-N'-benzylidene-1,2-diphenylethane (23.0 g, 57 mmol) in a mixture of glacial acetic acid (115 ml) and 48% aqueous HBr (230 ml) was heated to reflux for four days. The mixture was then cooled in an ice bath and diethyl ether (200 ml) was added and vigourous stirring was continued for 30 minutes before being filtered and washed with diethyl ether. The solid filtrate was added to 100 ml of ice-cold 40% aqueous NaOH, which was then extracted three times with CH2Cl2 (150 ml). The organic extracts were evaporated to dryness and recrystallized from water to obtain meso-1,2-diamino-1,2-diphenylethane (7.8 g, 65% yield). 1H NMR [400 MHz, CDCl3] δH 7.41–7.26 (m, 10H), 4.02 (s, 2H), 1.33 (s, 4H). 13C NMR [100 MHz, CDCl3] δC 142.8, 128.3, 127.5, 127.4, 62.7. A portion of this diamine (5.095 g, 24 mmol) was dissolved in CH2Cl2 (50 ml) and cooled in an ice bath, while a solution of 1,1'-carbonyldiimidazole (8.108 g, 50 mmol) in CH2Cl2 (250 ml) was added dropwise. The mixture was stirred for two hours, and the solvent was evaporated under reduced pressure. The solid was taken up in MeOH (200 ml), cooled in an ice bath, 20 ml of 40% aqueous NaOH was added, and the mixture was stirred for 30 minutes. Methanol was evaporated under reduced pressure, and the remaining aqueous solution was cooled in an ice bath and acidified to pH = 1 with 0.5 M HCl, upon which the title compound crystallized. The crystals were filtered to obtain meso-4,5-diphenylimidazolin-2-one (5.560 g, 97% yield). 1H NMR [400 MHz, CDCl3] δH 7.10–7.05 (m, 6H), 6.97–6.93 (m, 4H), 5.17 (s, 2H), 5.01 (broad s, 2H). 13C NMR [100 MHz, CDCl3] δC 163.5, 137.0, 128.0, 127.8, 127.0, 61.8.

Refinement top

H atoms bound to C were placed in calculated positions with C—H distances in the range 0.95–1.00Å and included in the refinement in a riding-model approximation with Uiso(H) = 1.2Ueq(C). The H atoms bonded to N atoms were refined independently with isotropic displacement parameters.

Computing details top

Data collection: COLLECT (Nonius, 2002); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure showing 30% probability displacement ellipsoids (arbitrary spheres for H atoms).
[Figure 2] Fig. 2. Part of the crystal structure showing hydrogen bonds as dashed lines.
[Figure 3] Fig. 3. The reaction scheme.
meso-4,5-Diphenylimidazolidin-2-one top
Crystal data top
C15H14N2OZ = 2
Mr = 238.28F(000) = 252
Triclinic, P1Dx = 1.327 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 6.3539 (4) ÅCell parameters from 6535 reflections
b = 8.6159 (4) Åθ = 3.0–27.5°
c = 11.3211 (7) ŵ = 0.09 mm1
α = 86.147 (3)°T = 150 K
β = 76.094 (3)°Plate, colourless
γ = 82.718 (3)°0.20 × 0.20 × 0.08 mm
V = 596.32 (6) Å3
Data collection top
Nonius KappaCCD
diffractometer
2685 independent reflections
Radiation source: fine-focus sealed tube1771 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.047
Detector resolution: 9 pixels mm-1θmax = 27.5°, θmin = 3.0°
ω scansh = 88
Absorption correction: multi-scan
(SORTAV; Blessing, 1995)
k = 1111
Tmin = 0.873, Tmax = 0.995l = 1214
6535 measured reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.054H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.156 w = 1/[σ2(Fo2) + (0.0787P)2 + 0.1078P]
where P = (Fo2 + 2Fc2)/3
S = 1.03(Δ/σ)max < 0.001
2685 reflectionsΔρmax = 0.25 e Å3
172 parametersΔρmin = 0.25 e Å3
0 restraintsExtinction correction: SHELXTL (Version 6.1; Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.043 (9)
Crystal data top
C15H14N2Oγ = 82.718 (3)°
Mr = 238.28V = 596.32 (6) Å3
Triclinic, P1Z = 2
a = 6.3539 (4) ÅMo Kα radiation
b = 8.6159 (4) ŵ = 0.09 mm1
c = 11.3211 (7) ÅT = 150 K
α = 86.147 (3)°0.20 × 0.20 × 0.08 mm
β = 76.094 (3)°
Data collection top
Nonius KappaCCD
diffractometer
2685 independent reflections
Absorption correction: multi-scan
(SORTAV; Blessing, 1995)
1771 reflections with I > 2σ(I)
Tmin = 0.873, Tmax = 0.995Rint = 0.047
6535 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0540 restraints
wR(F2) = 0.156H atoms treated by a mixture of independent and constrained refinement
S = 1.03Δρmax = 0.25 e Å3
2685 reflectionsΔρmin = 0.25 e Å3
172 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
xyzUiso*/Ueq
O10.5277 (2)0.41749 (16)0.65182 (13)0.0402 (4)
N10.2254 (3)0.55213 (18)0.59441 (15)0.0298 (4)
N20.2105 (3)0.50802 (19)0.79050 (15)0.0310 (4)
C10.0274 (3)0.6470 (2)0.65473 (17)0.0264 (4)
H1A0.09380.63280.61560.032*
C20.3394 (3)0.4852 (2)0.67556 (18)0.0308 (5)
C30.0134 (3)0.5630 (2)0.78442 (17)0.0283 (5)
H3A0.09260.47010.78310.034*
C40.0525 (3)0.8203 (2)0.65330 (16)0.0243 (4)
C50.2551 (3)0.8742 (2)0.63592 (17)0.0288 (5)
H5A0.38290.80140.62670.035*
C60.2724 (3)1.0331 (2)0.63194 (18)0.0315 (5)
H6A0.41181.06870.61950.038*
C70.0879 (3)1.1399 (2)0.64589 (18)0.0318 (5)
H7A0.10041.24890.64300.038*
C80.1151 (3)1.0882 (2)0.66414 (17)0.0317 (5)
H8A0.24261.16140.67410.038*
C90.1316 (3)0.9287 (2)0.66781 (17)0.0278 (5)
H9A0.27130.89340.68050.033*
C100.1371 (3)0.6618 (2)0.88918 (16)0.0259 (4)
C110.0311 (3)0.7520 (2)0.94856 (17)0.0297 (5)
H11A0.12280.75140.92330.036*
C120.1480 (3)0.8430 (2)1.04446 (18)0.0338 (5)
H12A0.07350.90301.08520.041*
C130.3712 (3)0.8468 (2)1.08089 (18)0.0339 (5)
H13A0.45100.91031.14590.041*
C140.4787 (3)0.7580 (2)1.02265 (19)0.0364 (5)
H14A0.63280.76031.04790.044*
C150.3626 (3)0.6652 (2)0.92714 (17)0.0307 (5)
H15A0.43760.60390.88780.037*
H2N0.248 (3)0.441 (3)0.846 (2)0.035 (6)*
H1N0.297 (3)0.569 (2)0.514 (2)0.040 (6)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0377 (9)0.0356 (8)0.0365 (9)0.0126 (7)0.0019 (7)0.0053 (6)
N10.0339 (10)0.0250 (8)0.0261 (9)0.0018 (7)0.0011 (7)0.0002 (7)
N20.0309 (10)0.0292 (9)0.0270 (9)0.0048 (7)0.0014 (7)0.0069 (7)
C10.0257 (10)0.0249 (9)0.0265 (10)0.0011 (8)0.0025 (8)0.0022 (8)
C20.0338 (12)0.0231 (10)0.0314 (11)0.0017 (8)0.0030 (9)0.0025 (8)
C30.0265 (10)0.0236 (9)0.0324 (10)0.0035 (8)0.0019 (8)0.0000 (8)
C40.0262 (10)0.0269 (10)0.0189 (9)0.0010 (8)0.0048 (7)0.0006 (7)
C50.0279 (11)0.0279 (10)0.0299 (10)0.0008 (8)0.0070 (8)0.0013 (8)
C60.0328 (11)0.0335 (11)0.0296 (11)0.0088 (9)0.0077 (9)0.0003 (8)
C70.0420 (12)0.0253 (10)0.0270 (10)0.0048 (9)0.0056 (9)0.0015 (8)
C80.0334 (12)0.0284 (10)0.0292 (11)0.0047 (9)0.0041 (9)0.0001 (8)
C90.0245 (10)0.0302 (10)0.0275 (10)0.0021 (8)0.0047 (8)0.0006 (8)
C100.0262 (10)0.0227 (9)0.0259 (10)0.0024 (8)0.0026 (8)0.0057 (7)
C110.0269 (10)0.0310 (10)0.0296 (10)0.0081 (8)0.0017 (8)0.0013 (8)
C120.0444 (13)0.0292 (10)0.0277 (11)0.0119 (9)0.0045 (9)0.0012 (8)
C130.0402 (13)0.0303 (11)0.0258 (10)0.0024 (9)0.0009 (9)0.0001 (8)
C140.0262 (11)0.0460 (13)0.0326 (11)0.0013 (9)0.0024 (9)0.0032 (10)
C150.0288 (11)0.0336 (11)0.0288 (10)0.0052 (8)0.0047 (8)0.0001 (8)
Geometric parameters (Å, º) top
O1—C21.238 (2)C6—H6A0.9500
N1—C21.358 (3)C7—C81.382 (3)
N1—C11.456 (2)C7—H7A0.9500
N1—H1N0.93 (2)C8—C91.389 (3)
N2—C21.373 (3)C8—H8A0.9500
N2—C31.458 (3)C9—H9A0.9500
N2—H2N0.87 (2)C10—C111.389 (3)
C1—C41.520 (2)C10—C151.391 (3)
C1—C31.571 (3)C11—C121.387 (3)
C1—H1A1.0000C11—H11A0.9500
C3—C101.506 (3)C12—C131.375 (3)
C3—H3A1.0000C12—H12A0.9500
C4—C91.386 (3)C13—C141.380 (3)
C4—C51.389 (3)C13—H13A0.9500
C5—C61.384 (3)C14—C151.392 (3)
C5—H5A0.9500C14—H14A0.9500
C6—C71.379 (3)C15—H15A0.9500
C2—N1—C1111.46 (16)C5—C6—H6A119.9
C2—N1—H1N119.9 (13)C6—C7—C8119.96 (17)
C1—N1—H1N123.4 (13)C6—C7—H7A120.0
C2—N2—C3110.27 (16)C8—C7—H7A120.0
C2—N2—H2N113.6 (14)C7—C8—C9119.57 (18)
C3—N2—H2N124.9 (14)C7—C8—H8A120.2
N1—C1—C4113.60 (15)C9—C8—H8A120.2
N1—C1—C399.73 (14)C4—C9—C8121.04 (17)
C4—C1—C3114.88 (14)C4—C9—H9A119.5
N1—C1—H1A109.4C8—C9—H9A119.5
C4—C1—H1A109.4C11—C10—C15118.79 (18)
C3—C1—H1A109.4C11—C10—C3121.43 (17)
O1—C2—N1126.79 (18)C15—C10—C3119.77 (17)
O1—C2—N2125.27 (18)C12—C11—C10120.59 (18)
N1—C2—N2107.93 (17)C12—C11—H11A119.7
N2—C3—C10113.62 (16)C10—C11—H11A119.7
N2—C3—C1100.24 (14)C13—C12—C11120.32 (19)
C10—C3—C1116.28 (14)C13—C12—H12A119.8
N2—C3—H3A108.8C11—C12—H12A119.8
C10—C3—H3A108.8C12—C13—C14119.72 (19)
C1—C3—H3A108.8C12—C13—H13A120.1
C9—C4—C5118.61 (16)C14—C13—H13A120.1
C9—C4—C1119.26 (16)C13—C14—C15120.36 (19)
C5—C4—C1122.12 (16)C13—C14—H14A119.8
C6—C5—C4120.56 (18)C15—C14—H14A119.8
C6—C5—H5A119.7C10—C15—C14120.20 (18)
C4—C5—H5A119.7C10—C15—H15A119.9
C7—C6—C5120.26 (18)C14—C15—H15A119.9
C7—C6—H6A119.9
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1N···O1i0.93 (2)1.94 (2)2.864 (2)173 (2)
N2—H2N···Cg1ii0.87 (2)2.46 (2)3.322 (2)165 (2)
Symmetry codes: (i) x+1, y+1, z+1; (ii) x, y+1, z+2.

Experimental details

Crystal data
Chemical formulaC15H14N2O
Mr238.28
Crystal system, space groupTriclinic, P1
Temperature (K)150
a, b, c (Å)6.3539 (4), 8.6159 (4), 11.3211 (7)
α, β, γ (°)86.147 (3), 76.094 (3), 82.718 (3)
V3)596.32 (6)
Z2
Radiation typeMo Kα
µ (mm1)0.09
Crystal size (mm)0.20 × 0.20 × 0.08
Data collection
DiffractometerNonius KappaCCD
diffractometer
Absorption correctionMulti-scan
(SORTAV; Blessing, 1995)
Tmin, Tmax0.873, 0.995
No. of measured, independent and
observed [I > 2σ(I)] reflections
6535, 2685, 1771
Rint0.047
(sin θ/λ)max1)0.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.054, 0.156, 1.03
No. of reflections2685
No. of parameters172
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.25, 0.25

Computer programs: COLLECT (Nonius, 2002), DENZO-SMN (Otwinowski & Minor, 1997), SIR92 (Altomare et al., 1994), SHELXTL (Sheldrick, 2008), PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1N···O1i0.93 (2)1.94 (2)2.864 (2)173 (2)
N2—H2N···Cg1ii0.87 (2)2.46 (2)3.322 (2)165 (2)
Symmetry codes: (i) x+1, y+1, z+1; (ii) x, y+1, z+2.
 

Acknowledgements

The authors are grateful for financial support from the American Chemical Society Petroleum Research Fund, the Dean's Seed Fund Initiative (Ryerson University), NSERC Canada and the University of Toronto.

References

First citationAltomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994). J. Appl. Cryst. 27, 435.  CrossRef Web of Science IUCr Journals Google Scholar
First citationBiniecki, S. & Moll, M. (1974). Acta Pol. Pharm. 31, 731–734.  CAS PubMed Google Scholar
First citationBlessing, R. H. (1995). Acta Cryst. A51, 33–38.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationIsobe, T., Fukuda, K. & Ishikawa, T. (1998). Tetrahedron Asymmetry, 9, 1729–1735.  Web of Science CrossRef CAS Google Scholar
First citationLou, Y., Horikawa, M., Kloster, R. A., Hawryluk, N. A. & Corey, E. J. (2004). J. Am. Chem. Soc. 126, 8916–8918.  Web of Science CSD CrossRef PubMed CAS Google Scholar
First citationNonius (2002). COLLECT. Nonius BV, Delft, The Netherlands.  Google Scholar
First citationOtwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307–326. New York: Academic Press.  Google Scholar
First citationPorosa, L. & Viirre, R. D. (2009). Tetrahedron Lett. 50, 4170–4173.  Web of Science CrossRef CAS Google Scholar
First citationProskurnina, M. V., Lozinskaya, N. A., Tkachenko, S. E. & Zefirov, N. S. (2002). Russ. J. Org. Chem. 8, 1149–1153.  Web of Science CrossRef Google Scholar
First citationSankhavasi, W., Yamamoto, M., Kohmoto, S. & Yamada, K. (1991). Bull. Chem. Soc. Jpn, 64, 1425–1427.  CrossRef CAS Web of Science Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSiegler, M. & Long, S. (2006). Acta Cryst. E62, o5310–o5311.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationSpek, A. L. (2009). Acta Cryst. D65, 148–155.  Web of Science CrossRef CAS IUCr Journals Google Scholar

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