research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2056-9890

Crystal structure of racemic cis-2-amino-1,2-di­phenyl­ethanol (ADE)

aSchool of Science, Tokai University, 4-1-1 Kitakaname, Hiratuka, Kanagawa 259-1292, Japan
*Correspondence e-mail: fujii@wing.ncc.u-tokai.ac.jp

Edited by H. Stoeckli-Evans, University of Neuchâtel, Switzerland (Received 11 November 2015; accepted 20 November 2015; online 28 November 2015)

In the title racemic compound, C14H15NO, the hy­droxy and amino groups form a bent tweezer-like motif towards the phenyl groups. In the crystal, enanti­omers aggregate with each other and are linked by O—H⋯N hydrogen bonds, forming chiral 21-helical columnar structures from C(5) chains along the b-axis direction. Left- and right-handed 21 helices are formed from (1S,2R)-2-amino-1,2-di­phenyl­ethanol and (1R,2S)-2-amino-1,2-di­phenyl­ethanol, respectively.

1. Chemical context

The production of chiral compounds has great importance in the pharmaceutical industry, and diastereomer salt separation is still widely applied in the process. An optical resolving agent, chiral 2-amino-1,2-di­phenyl­ethanol (ADE) (Read & Steele, 1927[Read, J. & Steele, C. C. (1927). J. Chem. Soc. pp. 910-918.]), has been widely tried and used in diastereomer salt separation methods; for example, chiral discrimination of 2-aryl­alkanoic acids by (1R,2S)-ADE (cis-isomer) (Kinbara et al., 1998[Kinbara, K., Kobayashi, Y. & Saigo, K. (1998). J. Chem. Soc. Perkin Trans. 2, pp. 1767-1776.]). The ADE mol­ecule with two adjacent stereogenic centers exists as diastereoisomers (and more, enanti­omers of cis- and trans-forms), and can be purchased without difficulty. It was considered that cis- and trans-ADE have different properties and play different roles in diastereomer salt separations. In fact, co-crystal structures with cis-ADE enanti­omers have been found in previous reports. The racemic structure of trans-ADE has been reported (Bari et al., 2012[Bari, A., Al-Obaid, A. M. & Ng, S. W. (2012). Acta Cryst. E68, o491.]), but that of cis-ADE has not. The crystal structure of racemic cis-ADE is reported on herein.

[Scheme 1]

2. Structural commentary

In the title compound (cis-ADE), Fig. 1[link], the hy­droxy and amino groups form a tweezer-like motif. Selected geometrical parameters are given in Table 1[link]. The dihedral angle between the phenyl rings is 50.29 (6)° and the torsion angle O1—C1—C2—N1 is 59.72 (11)°. These values are similar to those observed for trans-ADE (Bari et al., 2012[Bari, A., Al-Obaid, A. M. & Ng, S. W. (2012). Acta Cryst. E68, o491.]), viz. 48.05 (5) and 54.01 (10)°, respectively. However, in cis-ADE the hydroxyl group against the opposed phenyl ring adopts a gauche conformation [O1—C1—C2—C9 = −67.39 (11)°] compared to a trans conformation in trans-ADE. Thus a tweezer-like motif bent against the phenyl groups is seen in cis-ADE versus a projected motif in trans-ADE. The arrangements are similar to those found in the diastereomer salts with cis-enanti­omers, except for (1R,2S)-2-ammonio-1,2-di­phenyl­ethanol (Imai et al., 2008[Imai, Y., Kawaguchi, K., Matsuno, H., Sato, T., Kuroda, R. & Matsubara, Y. (2008). Tetrahedron, 64, 4585-4589.]).

Table 1
Selected geometric parameters (Å, °)

O1—C1 1.4213 (14) N1—C2 1.4732 (15)
       
O1—C1—C3 112.57 (9) N1—C2—C9 115.19 (9)
O1—C1—C2 107.90 (9) N1—C2—C1 106.72 (9)
       
O1—C1—C2—N1 59.72 (11) C3—C1—C2—N1 −175.47 (9)
O1—C1—C2—C9 −67.39 (11) C3—C1—C2—C9 57.42 (12)
[Figure 1]
Figure 1
A view of the mol­ecular structure of cis-(1S,2R)-ADE, with atom and ring labelling. Displacement ellipsoids are drawn at the 50% probability level.

3. Supra­molecular features

In the crystal, enanti­omers aggregate separately and are linked by O1—H13⋯N1 = [2.7977 (16) Å] hydrogen bonds, forming chiral 21-helical columnar structures from C(5) chains along the b-axis direction (Table 2[link] and Fig. 2[link]): Left- and right-handed 21 helices are formed from (1S, 2R)-ADE and (1R, 2S)-ADE, respectively. The hydro­phobic columnar structures surrounded by phenyl groups are consolidated by the C—H⋯π and N—H⋯π inter­actions, forming slabs parallel to the ab plane (Table 2[link] and Fig. 2[link]). This is in contrast to the columnar structure stacking of racemic R22(10) ring dimers from the O—H⋯N hydrogen bonds observed in the crystal structure of trans-ADE (Bari et al., 2012[Bari, A., Al-Obaid, A. M. & Ng, S. W. (2012). Acta Cryst. E68, o491.]).

Table 2
Hydrogen-bond geometry (Å, °)

CgA and CgB are the centroids of rings C3–C8 and C9–C14, respectively.

D—H⋯A D—H H⋯A DA D—H⋯A
O1—H13⋯N1i 0.95 (2) 1.86 (2) 2.7977 (16) 173.1 (16)
N1—H15⋯CgBii 0.88 (2) 2.670 (19) 3.5125 (14) 160.3 (15)
C12—H10⋯CgAiii 0.93 2.80 3.6780 (17) 158
Symmetry codes: (i) [-x+{\script{3\over 2}}, y+{\script{1\over 2}}, -z+1]; (ii) -x+2, -y+1, -z+1; (iii) [x+{\script{1\over 2}}, -y+{\script{3\over 2}}, z].
[Figure 2]
Figure 2
A partial view of the crystal packing of the title compound. Dashed lines indicate the hydrogen bonds, and C—H⋯π and N—H⋯π inter­actions (see Table 2[link]).

4. Synthesis and crystallization

cis-Enanti­omers of 2-amino-1,2-di­phenyl­ethanol (ADE) were purchased from Sigma–Aldrich Co. Ltd. Equivalent weights were mixed in a bottle. Plate-like colourless crystals of the title racemic compound were obtained by vapour-phase diffusion of an aqueous ethanol solution at 297 K.

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3[link]. All H atoms were located in difference Fourier maps. The NH2 and OH H atoms were freely refined. The C-bound H atoms were included in calculated positions and treated as riding atoms: C—H = 0.93–0.98 Å with Uiso(H) = 1.2Ueq(C).

Table 3
Experimental details

Crystal data
Chemical formula C14H15NO
Mr 213.27
Crystal system, space group Monoclinic, P21/a
Temperature (K) 297
a, b, c (Å) 16.7752 (17), 5.7573 (10), 12.2887 (13)
β (°) 105.680 (7)
V3) 1142.7 (3)
Z 4
Radiation type Cu Kα
μ (mm−1) 0.61
Crystal size (mm) 0.30 × 0.30 × 0.20
 
Data collection
Diffractometer Entaf–Nonius CAD-4
Absorption correction ψ scan (North et al., 1968[North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351-359.])
Tmin, Tmax 0.83, 0.90
No. of measured, independent and observed [I > 2σ(I)] reflections 2442, 2354, 2058
Rint 0.019
(sin θ/λ)max−1) 0.626
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.037, 0.105, 1.03
No. of reflections 2354
No. of parameters 158
H-atom treatment H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3) 0.22, −0.18
Computer programs: CAD-4 Software (Enraf–Nonius, 1989[Enraf-Nonius (1989). CAD-4 Software. Enraf-Nonius, Delft, The Netherlands.]), XCAD4 (Harms & Wocadlo, 1995[Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany.]), SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), SHELXL2014/7 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]), ORTEP-3 for Windows and WinGX (Farrugia, 2012[Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849-854.]), Mercury (Macrae et al., 2008[Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466-470.]), PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information


Computing details top

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software (Enraf–Nonius, 1989); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al., 2008); software used to prepare material for publication: PLATON (Spek, 2009), publCIF (Westrip, 2010), and WinGX (Farrugia, 2012).

cis-2-Amino-1,2-diphenylethanol top
Crystal data top
C14H15NOF(000) = 456
Mr = 213.27Dx = 1.240 Mg m3
Monoclinic, P21/aCu Kα radiation, λ = 1.54178 Å
Hall symbol: -P 2yabCell parameters from 25 reflections
a = 16.7752 (17) Åθ = 20–25°
b = 5.7573 (10) ŵ = 0.61 mm1
c = 12.2887 (13) ÅT = 297 K
β = 105.680 (7)°Plate, colourless
V = 1142.7 (3) Å30.30 × 0.30 × 0.20 mm
Z = 4
Data collection top
Entaf–Nonius CAD-4
diffractometer
2058 reflections with I > 2σ(I)
Radiation source: tube sealedRint = 0.019
Graphite monochromatorθmax = 74.9°, θmin = 3.7°
2θω scanh = 210
Absorption correction: ψ scan
(North et al., 1968)
k = 70
Tmin = 0.83, Tmax = 0.90l = 1415
2442 measured reflections3 standard reflections every 300 reflections
2354 independent reflections intensity decay: none
Refinement top
Refinement on F2H atoms treated by a mixture of independent and constrained refinement
Least-squares matrix: full W = 1/[Σ2(FO2) + (0.0588P)2 + 0.2117P] WHERE P = (FO2 + 2FC2)/3
R[F2 > 2σ(F2)] = 0.037(Δ/σ)max < 0.001
wR(F2) = 0.105Δρmax = 0.22 e Å3
S = 1.03Δρmin = 0.18 e Å3
2354 reflectionsExtinction correction: SHELXL2014/7 (Sheldrick, 2015), FC*=KFC[1+0.001XFC2Λ3/SIN(2Θ)]-1/4
158 parametersExtinction coefficient: 0.0107 (9)
0 restraintsAbsolute structure: see text
Hydrogen site location: mixed
Special details top

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles

Refinement. Refinement on F2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The observed criterion of F2 > σ(F2) is used only for calculating -R-factor-obs 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
O10.76749 (6)0.89601 (14)0.38299 (7)0.0445 (3)
N10.85894 (7)0.5703 (2)0.53117 (9)0.0478 (3)
C10.75159 (7)0.65596 (19)0.36005 (9)0.0359 (3)
C20.83327 (6)0.5226 (2)0.40885 (9)0.0370 (3)
C30.71413 (6)0.60757 (19)0.23561 (9)0.0347 (3)
C40.67124 (8)0.4020 (2)0.20194 (10)0.0438 (3)
C50.63480 (9)0.3576 (2)0.08879 (12)0.0514 (4)
C60.64086 (8)0.5178 (3)0.00766 (10)0.0527 (4)
C70.68404 (8)0.7206 (3)0.04003 (10)0.0516 (4)
C80.72072 (7)0.7658 (2)0.15340 (10)0.0427 (3)
C90.89766 (6)0.57714 (19)0.34642 (9)0.0352 (3)
C100.91137 (8)0.4216 (2)0.26755 (11)0.0458 (4)
C110.96758 (8)0.4696 (3)0.20612 (11)0.0552 (4)
C121.01117 (8)0.6743 (3)0.22244 (11)0.0521 (4)
C130.99884 (8)0.8302 (2)0.30109 (12)0.0517 (4)
C140.94275 (8)0.7827 (2)0.36305 (11)0.0454 (4)
H10.711900.605000.400800.0430*
H20.820700.356400.399200.0440*
H30.667000.293200.256000.0530*
H40.606100.219500.067200.0620*
H50.615900.488600.068400.0630*
H60.688700.828100.014400.0620*
H70.749900.903300.174400.0510*
H80.882300.282200.255500.0550*
H90.975800.362600.153500.0660*
H101.048600.707200.180800.0630*
H111.028400.968900.312900.0620*
H120.935300.889500.416200.0540*
H130.7225 (12)0.959 (3)0.4061 (15)0.077 (5)*
H140.8637 (12)0.732 (4)0.5400 (16)0.085 (6)*
H150.9080 (12)0.508 (3)0.5611 (15)0.074 (5)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0495 (5)0.0365 (4)0.0494 (5)0.0033 (4)0.0169 (4)0.0058 (3)
N10.0460 (6)0.0600 (7)0.0362 (5)0.0006 (5)0.0089 (4)0.0094 (5)
C10.0370 (5)0.0355 (5)0.0375 (5)0.0012 (4)0.0138 (4)0.0019 (4)
C20.0378 (6)0.0353 (6)0.0381 (5)0.0000 (4)0.0106 (4)0.0049 (4)
C30.0315 (5)0.0362 (6)0.0374 (5)0.0048 (4)0.0108 (4)0.0026 (4)
C40.0496 (6)0.0368 (6)0.0456 (6)0.0001 (5)0.0140 (5)0.0032 (5)
C50.0540 (7)0.0442 (7)0.0536 (7)0.0054 (6)0.0102 (6)0.0083 (6)
C60.0535 (7)0.0617 (8)0.0390 (6)0.0018 (6)0.0059 (5)0.0046 (6)
C70.0566 (7)0.0565 (8)0.0400 (6)0.0017 (6)0.0104 (5)0.0096 (6)
C80.0430 (6)0.0419 (6)0.0427 (6)0.0041 (5)0.0108 (5)0.0047 (5)
C90.0321 (5)0.0346 (5)0.0378 (5)0.0039 (4)0.0077 (4)0.0051 (4)
C100.0417 (6)0.0437 (7)0.0525 (7)0.0027 (5)0.0138 (5)0.0079 (5)
C110.0465 (7)0.0714 (9)0.0508 (7)0.0004 (6)0.0186 (6)0.0137 (7)
C120.0375 (6)0.0719 (9)0.0495 (7)0.0009 (6)0.0162 (5)0.0087 (6)
C130.0431 (6)0.0468 (7)0.0669 (8)0.0062 (5)0.0176 (6)0.0070 (6)
C140.0453 (6)0.0382 (6)0.0548 (7)0.0019 (5)0.0171 (5)0.0028 (5)
Geometric parameters (Å, º) top
O1—C11.4213 (14)C10—C111.386 (2)
N1—C21.4732 (15)C11—C121.373 (2)
O1—H130.95 (2)C12—C131.375 (2)
C1—C31.5138 (15)C13—C141.388 (2)
N1—H150.88 (2)C1—H10.9800
N1—H140.94 (2)C2—H20.9800
C1—C21.5435 (16)C4—H30.9300
C2—C91.5172 (15)C5—H40.9300
C3—C81.3868 (16)C6—H50.9300
C3—C41.3888 (16)C7—H60.9300
C4—C51.3831 (19)C8—H70.9300
C5—C61.382 (2)C10—H80.9300
C6—C71.375 (2)C11—H90.9300
C7—C81.3870 (17)C12—H100.9300
C9—C141.3896 (16)C13—H110.9300
C9—C101.3837 (17)C14—H120.9300
C1—O1—H13108.0 (11)O1—C1—H1108.00
O1—C1—C3112.57 (9)C2—C1—H1108.00
C2—C1—C3112.55 (9)C3—C1—H1108.00
H14—N1—H15108.3 (17)N1—C2—H2107.00
O1—C1—C2107.90 (9)C1—C2—H2107.00
C2—N1—H14107.2 (12)C9—C2—H2107.00
C2—N1—H15109.4 (12)C3—C4—H3120.00
N1—C2—C9115.19 (9)C5—C4—H3120.00
C1—C2—C9112.28 (9)C4—C5—H4120.00
N1—C2—C1106.72 (9)C6—C5—H4120.00
C1—C3—C4119.87 (10)C5—C6—H5120.00
C1—C3—C8121.46 (10)C7—C6—H5120.00
C4—C3—C8118.66 (10)C6—C7—H6120.00
C3—C4—C5120.64 (11)C8—C7—H6120.00
C4—C5—C6120.21 (12)C3—C8—H7120.00
C5—C6—C7119.59 (12)C7—C8—H7120.00
C6—C7—C8120.39 (13)C9—C10—H8119.00
C3—C8—C7120.49 (12)C11—C10—H8119.00
C2—C9—C10119.74 (10)C10—C11—H9120.00
C2—C9—C14122.38 (10)C12—C11—H9120.00
C10—C9—C14117.86 (11)C11—C12—H10120.00
C9—C10—C11121.26 (12)C13—C12—H10120.00
C10—C11—C12120.37 (13)C12—C13—H11120.00
C11—C12—C13119.19 (13)C14—C13—H11120.00
C12—C13—C14120.66 (12)C9—C14—H12120.00
C9—C14—C13120.65 (11)C13—C14—H12120.00
O1—C1—C2—N159.72 (11)C1—C3—C8—C7178.29 (12)
O1—C1—C2—C967.39 (11)C4—C3—C8—C70.98 (18)
C3—C1—C2—N1175.47 (9)C3—C4—C5—C60.1 (2)
C3—C1—C2—C957.42 (12)C4—C5—C6—C70.6 (2)
O1—C1—C3—C4159.70 (11)C5—C6—C7—C80.6 (2)
O1—C1—C3—C819.56 (15)C6—C7—C8—C30.2 (2)
C2—C1—C3—C478.10 (13)C2—C9—C10—C11177.69 (11)
C2—C1—C3—C8102.65 (12)C14—C9—C10—C110.64 (18)
N1—C2—C9—C10136.09 (11)C2—C9—C14—C13177.49 (11)
N1—C2—C9—C1445.66 (15)C10—C9—C14—C130.80 (18)
C1—C2—C9—C10101.48 (12)C9—C10—C11—C120.0 (2)
C1—C2—C9—C1476.77 (13)C10—C11—C12—C130.5 (2)
C1—C3—C4—C5178.33 (12)C11—C12—C13—C140.4 (2)
C8—C3—C4—C50.94 (19)C12—C13—C14—C90.3 (2)
Hydrogen-bond geometry (Å, º) top
CgA and CgB are the centroids of rings C3–C8 and C9–C14, respectively.
D—H···AD—HH···AD···AD—H···A
O1—H13···N1i0.95 (2)1.86 (2)2.7977 (16)173.1 (16)
N1—H15···CgBii0.88 (2)2.670 (19)3.5125 (14)160.3 (15)
C12—H10···CgAiii0.932.803.6780 (17)158
Symmetry codes: (i) x+3/2, y+1/2, z+1; (ii) x+2, y+1, z+1; (iii) x+1/2, y+3/2, z.
 

Acknowledgements

The author thanks Tokai University for a research grant, which partially supported this work.

References

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