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

Fujii, I.

doi:10.1107/S2056989015022318

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Volume 71| Part 12| December 2015| Pages 1539-1541

https://doi.org/10.1107/S2056989015022318

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

Isao Fujii ^a ^*

^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.

Keywords: crystal structure; optical resolving agent; 2₁-helical columnar structure; intermolecular hydrogen bonding; C—H⋯π and N—H⋯π interactions.

CCDC reference: 1438134

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 ), 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 ). 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 ), but that of cis-ADE has not. The crystal structure of racemic cis-ADE is reported on herein.

2. Structural commentary

In the title compound (cis-ADE), Fig. 1, the hydroxy and amino groups form a tweezer-like motif. Selected geometrical parameters are given in Table 1. 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), 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 ).

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
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 and Fig. 2): 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 and Fig. 2). 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).

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	D⋯A	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
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

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. 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 U_iso(H) = 1.2U_eq(C).

Table 3
Experimental details

Crystal data
Chemical formula	C₁₄H₁₅NO
M_r	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)
V (Å³)	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 )
T_min, T_max	0.83, 0.90
No. of measured, independent and observed [I > 2σ(I)] reflections	2442, 2354, 2058
R_int	0.019
(sin θ/λ)_max (Å⁻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
Δρ_max, Δρ_min (e Å⁻³)	0.22, −0.18
Computer programs: CAD-4 Software (Enraf–Nonius, 1989 ), XCAD4 (Harms & Wocadlo, 1995 ), SHELXS97 (Sheldrick, 2008 ), SHELXL2014/7 (Sheldrick, 2015 ), ORTEP-3 for Windows and WinGX (Farrugia, 2012 ), Mercury (Macrae et al., 2008 ), PLATON (Spek, 2009 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 1438134

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S2056989015022318/su5243sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989015022318/su5243Isup2.hkl

checkCIF report

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

C₁₄H₁₅NO	F(000) = 456
M_r = 213.27	D_x = 1.240 Mg m⁻³
Monoclinic, P2₁/a	Cu Kα radiation, λ = 1.54178 Å
Hall symbol: -P 2yab	Cell parameters from 25 reflections
a = 16.7752 (17) Å	θ = 20–25°
b = 5.7573 (10) Å	µ = 0.61 mm⁻¹
c = 12.2887 (13) Å	T = 297 K
β = 105.680 (7)°	Plate, colourless
V = 1142.7 (3) Å³	0.30 × 0.30 × 0.20 mm
Z = 4

Data collection top

Entaf–Nonius CAD-4 diffractometer	2058 reflections with I > 2σ(I)
Radiation source: tube sealed	R_int = 0.019
Graphite monochromator	θ_max = 74.9°, θ_min = 3.7°
2θ–ω scan	h = −21→0
Absorption correction: ψ scan (North et al., 1968)	k = −7→0
T_min = 0.83, T_max = 0.90	l = −14→15
2442 measured reflections	3 standard reflections every 300 reflections
2354 independent reflections	intensity decay: none

Refinement top

Refinement on F²	H 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) = 0.105	Δρ_max = 0.22 e Å⁻³
S = 1.03	Δρ_min = −0.18 e Å⁻³
2354 reflections	Extinction correction: SHELXL2014/7 (Sheldrick, 2015), FC^*=KFC[1+0.001XFC²Λ³/SIN(2Θ)]^-1/4
158 parameters	Extinction coefficient: 0.0107 (9)
0 restraints	Absolute 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

	x	y	z	U_iso*/U_eq
O1	0.76749 (6)	0.89601 (14)	0.38299 (7)	0.0445 (3)
N1	0.85894 (7)	0.5703 (2)	0.53117 (9)	0.0478 (3)
C1	0.75159 (7)	0.65596 (19)	0.36005 (9)	0.0359 (3)
C2	0.83327 (6)	0.5226 (2)	0.40885 (9)	0.0370 (3)
C3	0.71413 (6)	0.60757 (19)	0.23561 (9)	0.0347 (3)
C4	0.67124 (8)	0.4020 (2)	0.20194 (10)	0.0438 (3)
C5	0.63480 (9)	0.3576 (2)	0.08879 (12)	0.0514 (4)
C6	0.64086 (8)	0.5178 (3)	0.00766 (10)	0.0527 (4)
C7	0.68404 (8)	0.7206 (3)	0.04003 (10)	0.0516 (4)
C8	0.72072 (7)	0.7658 (2)	0.15340 (10)	0.0427 (3)
C9	0.89766 (6)	0.57714 (19)	0.34642 (9)	0.0352 (3)
C10	0.91137 (8)	0.4216 (2)	0.26755 (11)	0.0458 (4)
C11	0.96758 (8)	0.4696 (3)	0.20612 (11)	0.0552 (4)
C12	1.01117 (8)	0.6743 (3)	0.22244 (11)	0.0521 (4)
C13	0.99884 (8)	0.8302 (2)	0.30109 (12)	0.0517 (4)
C14	0.94275 (8)	0.7827 (2)	0.36305 (11)	0.0454 (4)
H1	0.71190	0.60500	0.40080	0.0430*
H2	0.82070	0.35640	0.39920	0.0440*
H3	0.66700	0.29320	0.25600	0.0530*
H4	0.60610	0.21950	0.06720	0.0620*
H5	0.61590	0.48860	−0.06840	0.0630*
H6	0.68870	0.82810	−0.01440	0.0620*
H7	0.74990	0.90330	0.17440	0.0510*
H8	0.88230	0.28220	0.25550	0.0550*
H9	0.97580	0.36260	0.15350	0.0660*
H10	1.04860	0.70720	0.18080	0.0630*
H11	1.02840	0.96890	0.31290	0.0620*
H12	0.93530	0.88950	0.41620	0.0540*
H13	0.7225 (12)	0.959 (3)	0.4061 (15)	0.077 (5)*
H14	0.8637 (12)	0.732 (4)	0.5400 (16)	0.085 (6)*
H15	0.9080 (12)	0.508 (3)	0.5611 (15)	0.074 (5)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0495 (5)	0.0365 (4)	0.0494 (5)	0.0033 (4)	0.0169 (4)	−0.0058 (3)
N1	0.0460 (6)	0.0600 (7)	0.0362 (5)	−0.0006 (5)	0.0089 (4)	0.0094 (5)
C1	0.0370 (5)	0.0355 (5)	0.0375 (5)	0.0012 (4)	0.0138 (4)	0.0019 (4)
C2	0.0378 (6)	0.0353 (6)	0.0381 (5)	0.0000 (4)	0.0106 (4)	0.0049 (4)
C3	0.0315 (5)	0.0362 (6)	0.0374 (5)	0.0048 (4)	0.0108 (4)	0.0026 (4)
C4	0.0496 (6)	0.0368 (6)	0.0456 (6)	−0.0001 (5)	0.0140 (5)	0.0032 (5)
C5	0.0540 (7)	0.0442 (7)	0.0536 (7)	−0.0054 (6)	0.0102 (6)	−0.0083 (6)
C6	0.0535 (7)	0.0617 (8)	0.0390 (6)	0.0018 (6)	0.0059 (5)	−0.0046 (6)
C7	0.0566 (7)	0.0565 (8)	0.0400 (6)	−0.0017 (6)	0.0104 (5)	0.0096 (6)
C8	0.0430 (6)	0.0419 (6)	0.0427 (6)	−0.0041 (5)	0.0108 (5)	0.0047 (5)
C9	0.0321 (5)	0.0346 (5)	0.0378 (5)	0.0039 (4)	0.0077 (4)	0.0051 (4)
C10	0.0417 (6)	0.0437 (7)	0.0525 (7)	−0.0027 (5)	0.0138 (5)	−0.0079 (5)
C11	0.0465 (7)	0.0714 (9)	0.0508 (7)	−0.0004 (6)	0.0186 (6)	−0.0137 (7)
C12	0.0375 (6)	0.0719 (9)	0.0495 (7)	0.0009 (6)	0.0162 (5)	0.0087 (6)
C13	0.0431 (6)	0.0468 (7)	0.0669 (8)	−0.0062 (5)	0.0176 (6)	0.0070 (6)
C14	0.0453 (6)	0.0382 (6)	0.0548 (7)	−0.0019 (5)	0.0171 (5)	−0.0028 (5)

Geometric parameters (Å, º) top

O1—C1	1.4213 (14)	C10—C11	1.386 (2)
N1—C2	1.4732 (15)	C11—C12	1.373 (2)
O1—H13	0.95 (2)	C12—C13	1.375 (2)
C1—C3	1.5138 (15)	C13—C14	1.388 (2)
N1—H15	0.88 (2)	C1—H1	0.9800
N1—H14	0.94 (2)	C2—H2	0.9800
C1—C2	1.5435 (16)	C4—H3	0.9300
C2—C9	1.5172 (15)	C5—H4	0.9300
C3—C8	1.3868 (16)	C6—H5	0.9300
C3—C4	1.3888 (16)	C7—H6	0.9300
C4—C5	1.3831 (19)	C8—H7	0.9300
C5—C6	1.382 (2)	C10—H8	0.9300
C6—C7	1.375 (2)	C11—H9	0.9300
C7—C8	1.3870 (17)	C12—H10	0.9300
C9—C14	1.3896 (16)	C13—H11	0.9300
C9—C10	1.3837 (17)	C14—H12	0.9300

C1—O1—H13	108.0 (11)	O1—C1—H1	108.00
O1—C1—C3	112.57 (9)	C2—C1—H1	108.00
C2—C1—C3	112.55 (9)	C3—C1—H1	108.00
H14—N1—H15	108.3 (17)	N1—C2—H2	107.00
O1—C1—C2	107.90 (9)	C1—C2—H2	107.00
C2—N1—H14	107.2 (12)	C9—C2—H2	107.00
C2—N1—H15	109.4 (12)	C3—C4—H3	120.00
N1—C2—C9	115.19 (9)	C5—C4—H3	120.00
C1—C2—C9	112.28 (9)	C4—C5—H4	120.00
N1—C2—C1	106.72 (9)	C6—C5—H4	120.00
C1—C3—C4	119.87 (10)	C5—C6—H5	120.00
C1—C3—C8	121.46 (10)	C7—C6—H5	120.00
C4—C3—C8	118.66 (10)	C6—C7—H6	120.00
C3—C4—C5	120.64 (11)	C8—C7—H6	120.00
C4—C5—C6	120.21 (12)	C3—C8—H7	120.00
C5—C6—C7	119.59 (12)	C7—C8—H7	120.00
C6—C7—C8	120.39 (13)	C9—C10—H8	119.00
C3—C8—C7	120.49 (12)	C11—C10—H8	119.00
C2—C9—C10	119.74 (10)	C10—C11—H9	120.00
C2—C9—C14	122.38 (10)	C12—C11—H9	120.00
C10—C9—C14	117.86 (11)	C11—C12—H10	120.00
C9—C10—C11	121.26 (12)	C13—C12—H10	120.00
C10—C11—C12	120.37 (13)	C12—C13—H11	120.00
C11—C12—C13	119.19 (13)	C14—C13—H11	120.00
C12—C13—C14	120.66 (12)	C9—C14—H12	120.00
C9—C14—C13	120.65 (11)	C13—C14—H12	120.00

O1—C1—C2—N1	59.72 (11)	C1—C3—C8—C7	−178.29 (12)
O1—C1—C2—C9	−67.39 (11)	C4—C3—C8—C7	0.98 (18)
C3—C1—C2—N1	−175.47 (9)	C3—C4—C5—C6	0.1 (2)
C3—C1—C2—C9	57.42 (12)	C4—C5—C6—C7	0.6 (2)
O1—C1—C3—C4	−159.70 (11)	C5—C6—C7—C8	−0.6 (2)
O1—C1—C3—C8	19.56 (15)	C6—C7—C8—C3	−0.2 (2)
C2—C1—C3—C4	78.10 (13)	C2—C9—C10—C11	177.69 (11)
C2—C1—C3—C8	−102.65 (12)	C14—C9—C10—C11	−0.64 (18)
N1—C2—C9—C10	136.09 (11)	C2—C9—C14—C13	−177.49 (11)
N1—C2—C9—C14	−45.66 (15)	C10—C9—C14—C13	0.80 (18)
C1—C2—C9—C10	−101.48 (12)	C9—C10—C11—C12	0.0 (2)
C1—C2—C9—C14	76.77 (13)	C10—C11—C12—C13	0.5 (2)
C1—C3—C4—C5	178.33 (12)	C11—C12—C13—C14	−0.4 (2)
C8—C3—C4—C5	−0.94 (19)	C12—C13—C14—C9	−0.3 (2)

Hydrogen-bond geometry (Å, º) top

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

D—H···A	D—H	H···A	D···A	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+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.

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