(1R*,2R*)-Di-tert-but­yl N,N′-(cyclo­hexane-1,2-di­yl)dicarbamate

Light, M.E.; Ragusa, A.; Kilburn, J.D.

doi:10.1107/S1600536805016715

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 61| Part 6| June 2005| Pages o1956-o1958

https://doi.org/10.1107/S1600536805016715

(1R,2R)-Di-tert-butyl N,N′-(cyclohexane-1,2-diyl)dicarbamate

Mark E. Light,^a ^* Andrea Ragusa ^a and Jeremy D. Kilburn ^a

^aSchool of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, England
^*Correspondence e-mail: light@soton.ac.uk

(Received 16 May 2005; accepted 25 May 2005; online 31 May 2005)

The title compound, C₁₆H₃₀N₂O₄, was synthesized as part of ongoing studies into enantioselective recognition. The molecule sits on a twofold axis and forms ladders via N—H⋯O hydrogen-bond pairs.

Comment

(1R*,2R*)-Di-tert-butyl N,N′-(cyclohexane-1,2-diyl)dicarbamate, (I), was synthesized as part of our ongoing studies into enantioselective recognition (Botana et al., 2001 ; Rossi et al., 2002 ; Kyne et al., 2001 ). The synthesis of new chiral receptors is a major challenge for chemists since it is very difficult to predict all the factors contributing to the binding process between a host and a guest in solution (Beer et al., 1999 ). Furthermore, the use of cheap and readily available building blocks for the construction of enantioselective receptors is of fundamental importance from an industrial point of view. To that aim, compound (I), with its two chiral centres and its amidic H atoms, is an appealing intermediate for the synthesis of more complicated structures, which may be able to discriminate between two enantiomers of a racemic mixture.

In the crystal structure, the molecule is disposed about a twofold crystallographic axis. The cyclohexane ring adopts a chair conformation, with methylcarbamic acid tert-butyl ester groups hanging down below to form a V-shaped molecule in which the NH groups point in opposite directions. This arrangement aids the formation of hydrogen-bonded ladders (Fig.2) that extend along the c direction via N—H⋯O hydrogen-bond pairs. When viewed down the c axis, the hydrogen-bonded ladders arrange themselves in a close-packed manner such that the `Vs' line up, all pointing in the same direction (Fig. 3).

Figure 1
View of the structure of (I)

, showing the atomic numbering scheme. Displacement ellipsoids for non-H atoms are drawn at the 35% probability level, and H atoms are drawn with arbitrary radii. [Symmetry code: (_1) −x + 1, y, −z.]

Figure 2
Part of one of the hydrogen-bonded ladders extending along c. Hydrogen bonds are shown as dotted lines. Only those H atoms involved in classical hydrogen bonds have been included.

Figure 3
A packing diagram viewed down c, showing the arrangement of the V-shaped molecules.

Experimental

(1S,2S)-1,2-Diphenyl-1,2-ethylenediamine-L-tartaric acid (1.6 g, 4.41 mmol) was dissolved in 1M K₂CO₃ (20 ml). A solution of di-tert-butyl dicarbonate (2.77 g, 12.7 mmol) in ethanol (40 ml) was added and the mixture was stirred at room temperature for 17 h. The solvents were removed in vacuo and the residue was dissolved in water to yield the product as a pale-yellow precipitate (1.3 g, 94%). The crystal for structure determination was obtained by slow evaporation of a 0.05 mM solution of the product in dimethyl sulfoxide (DMSO, 1 ml). M.p. 493–495 K. ¹H NMR (400 MHz, DMSO-d₆): δ 7.71 (2H, m, NH), 3.62 (2H, m, CH), 1.81 (2H, m, CHHCH), 1.66 (2H, m, CHHCH), 1.24 (18H, s, CH₃), 1.17 (4H, m, CH₂CH₂CH); ¹³C NMR (100 MHz, DMSO-d₆): δ 155.2 (0), 78.2 (0), 52.3 (1), 31.6 (2), 28.3 (3), 24.2 (2); m/z (ES⁺) 337.2 [M+Na]⁺; HRMS (ES⁺) Calculated for C₁₆H₃₁N₂O₄⁺: 315.2278; found: 315.2282. Analysis calculated for C₁₆H₃₀N₂O₄: C 61.12, H 9.62, N 8.91%; found: C 61.12, H 9.64, N 8.98%.

Crystal data

C₁₆H₃₀N₂O₄
M_r = 314.42
Monoclinic, C 2
a = 18.856 (4) Å
b = 9.3110 (19) Å
c = 5.183 (1) Å
β = 101.04 (3)°
V = 893.1 (3) Å³
Z = 2
D_x = 1.169 Mg m⁻³
Mo Kα radiation
Cell parameters from 982 reflections
θ = 2.9–27.5°
μ = 0.08 mm⁻¹
T = 120 (2) K
Slab, pale yellow
0.20 × 0.12 × 0.03 mm

Data collection

Nonius KappaCCD diffractometer
φ and ω scans
Absorption correction: multi-scan(SADABS; Sheldrick, 2003 )T_min = 0.984, T_max = 0.998
3861 measured reflections
1069 independent reflections
966 reflections with I > 2σ(I)
R_int = 0.045
θ_max = 27.5°
h = −23 → 24
k = −12 → 12
l = −6 → 6

Refinement

Refinement on F²
R[F² > 2σ(F²)] = 0.035
wR(F²) = 0.078
S = 1.06
1069 reflections
108 parameters
H atoms treated by a mixture of independent and constrained refinement
w = 1/[σ²(F_o²) + (0.0274P)² + 0.2768P] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max = 0.006
Δρ_max = 0.16 e Å⁻³
Δρ_min = −0.15 e Å⁻³
Extinction correction: SHELXL97
Extinction coefficient: 0.018 (5)

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H99⋯O2ⁱ	0.84 (2)	2.20 (3)	2.996 (2)	160 (2)
Symmetry code: (i) x, y, z-1.

In the absence of significant anomalous dispersion effects, Friedel pairs were merged. All C-bound H atoms were located in a difference Fourier map, and were placed in calculated positions and treated as riding on their parent atoms, with C—H = 0.98 Å and U_iso(H) = 1.5U_eq(C) for CH₃, C—H = 0.99 Å and U_iso(H) = 1.2U_eq(C) for CH₂, and C—H = 1.00 Å and U_iso(H) = 1.2U_eq(C) for CH. The single H atom on the N atom was freely refined.

Data collection: COLLECT (Hooft, 1998 ); cell refinement: DENZO (Otwinowski & Minor, 1997 ) and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997 ); molecular graphics: CAMERON (Watkin et al., 1993 ); software used to prepare material for publication: WinGX (Farrugia, 1999 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S1600536805016715/hg6193sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536805016715/hg6193Isup2.hkl

Computing details top

Data collection: COLLECT (Hooft, 1998); cell refinement: DENZO (Otwinowski & Minor, 1997) and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: CAMERON (Watkin et al., 1993); software used to prepare material for publication: WinGX (Farrugia, 1999).

(1R*,2R*)-Di-tert-butyl N,N'-(cyclohexane-1,2-diyl)dicarbamate top

Crystal data top

C₁₆H₃₀N₂O₄	F(000) = 344
M_r = 314.42	D_x = 1.169 Mg m⁻³
Monoclinic, C2	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: C 2y	Cell parameters from 982 reflections
a = 18.856 (4) Å	θ = 2.9–27.5°
b = 9.3110 (19) Å	µ = 0.08 mm⁻¹
c = 5.183 (1) Å	T = 120 K
β = 101.04 (3)°	Slab, pale yellow
V = 893.1 (3) Å³	0.20 × 0.12 × 0.03 mm
Z = 2

Data collection top

Nonius KappaCCD diffractometer	1069 independent reflections
Radiation source: Bruker Nonius FR591 Rotating Anode	966 reflections with I > 2σ(I)
10cm confocal mirrors monochromator	R_int = 0.045
Detector resolution: 9.091 pixels mm^-1	θ_max = 27.5°, θ_min = 4.0°
φ and ω scans	h = −23→24
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)	k = −12→12
T_min = 0.984, T_max = 0.998	l = −6→6
3861 measured reflections

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)] = 0.035	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.078	w = 1/[σ²(F_o²) + (0.0274P)² + 0.2768P] where P = (F_o² + 2F_c²)/3
S = 1.06	(Δ/σ)_max = 0.006
1069 reflections	Δρ_max = 0.16 e Å⁻³
108 parameters	Δρ_min = −0.15 e Å⁻³
1 restraint	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.018 (5)

Special details top

Experimental. SADABS was used to perform the Absorption correction Parameter refinement on 3374 reflections reduced R(int) from 0.1021 to 0.0430 Ratio of minimum to maximum apparent transmission: 0.825366 The given Tmin and Tmax were generated using the SHELX SIZE command

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
C1	0.37974 (12)	−0.2307 (2)	0.5011 (4)	0.0317 (5)
H1A	0.4177	−0.2702	0.4166	0.048*
H1B	0.3579	−0.3083	0.5870	0.048*
H1C	0.4007	−0.1593	0.6326	0.048*
C2	0.26751 (12)	−0.0748 (3)	0.4139 (4)	0.0297 (5)
H2A	0.2930	−0.0054	0.5409	0.045*
H2B	0.2396	−0.1406	0.5032	0.045*
H2C	0.2348	−0.0235	0.2744	0.045*
C3	0.28359 (12)	−0.2712 (3)	0.1034 (4)	0.0319 (5)
H3A	0.2484	−0.2233	−0.0331	0.048*
H3B	0.2586	−0.3398	0.1981	0.048*
H3C	0.3190	−0.3222	0.0218	0.048*
C4	0.32203 (11)	−0.1598 (2)	0.2946 (4)	0.0249 (5)
C5	0.39673 (10)	0.0463 (2)	0.2217 (4)	0.0237 (4)
C6	0.47084 (9)	0.2357 (2)	0.0855 (3)	0.0211 (4)
H6	0.4955	0.2347	0.2743	0.025*
C7	0.42526 (11)	0.3717 (2)	0.0363 (4)	0.0281 (5)
H7A	0.3983	0.3715	−0.1474	0.034*
H7B	0.3896	0.3722	0.1537	0.034*
C8	0.47087 (12)	0.5068 (2)	0.0837 (4)	0.0297 (5)
H8A	0.4938	0.5128	0.2719	0.036*
H8B	0.4395	0.5922	0.0400	0.036*
N1	0.42652 (9)	0.1078 (2)	0.0353 (3)	0.0252 (4)
O1	0.35630 (8)	−0.06813 (17)	0.1227 (2)	0.0271 (4)
O2	0.40471 (8)	0.08750 (17)	0.4484 (3)	0.0318 (4)
H99	0.4150 (12)	0.083 (3)	−0.122 (5)	0.028 (6)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0364 (12)	0.0310 (12)	0.0280 (11)	0.0049 (10)	0.0067 (9)	−0.0021 (9)
C2	0.0277 (11)	0.0334 (11)	0.0292 (11)	−0.0006 (10)	0.0080 (8)	0.0014 (10)
C3	0.0383 (12)	0.0309 (11)	0.0274 (11)	−0.0104 (11)	0.0083 (8)	−0.0001 (9)
C4	0.0288 (10)	0.0275 (11)	0.0190 (10)	−0.0042 (9)	0.0057 (7)	0.0022 (8)
C5	0.0210 (10)	0.0296 (11)	0.0198 (10)	−0.0030 (9)	0.0021 (7)	−0.0024 (8)
C6	0.0179 (9)	0.0266 (10)	0.0186 (10)	−0.0009 (9)	0.0033 (7)	−0.0012 (8)
C7	0.0235 (10)	0.0360 (12)	0.0257 (10)	0.0038 (10)	0.0070 (8)	−0.0008 (9)
C8	0.0354 (12)	0.0293 (12)	0.0244 (11)	0.0050 (10)	0.0060 (9)	−0.0013 (9)
N1	0.0284 (9)	0.0315 (10)	0.0163 (9)	−0.0098 (8)	0.0056 (7)	−0.0051 (7)
O1	0.0333 (8)	0.0314 (8)	0.0179 (7)	−0.0104 (7)	0.0080 (6)	−0.0025 (6)
O2	0.0373 (8)	0.0411 (9)	0.0177 (7)	−0.0125 (8)	0.0072 (6)	−0.0062 (6)

Geometric parameters (Å, º) top

C1—C4	1.523 (3)	C5—N1	1.336 (3)
C1—H1A	0.9800	C5—O1	1.353 (2)
C1—H1B	0.9800	C6—N1	1.450 (3)
C1—H1C	0.9800	C6—C7	1.524 (3)
C2—C4	1.519 (3)	C6—C6ⁱ	1.539 (4)
C2—H2A	0.9800	C6—H6	1.0000
C2—H2B	0.9800	C7—C8	1.517 (3)
C2—H2C	0.9800	C7—H7A	0.9900
C3—C4	1.519 (3)	C7—H7B	0.9900
C3—H3A	0.9800	C8—C8ⁱ	1.525 (4)
C3—H3B	0.9800	C8—H8A	0.9900
C3—H3C	0.9800	C8—H8B	0.9900
C4—O1	1.470 (2)	N1—H99	0.84 (2)
C5—O2	1.218 (2)

C4—C1—H1A	109.5	O2—C5—O1	124.81 (18)
C4—C1—H1B	109.5	N1—C5—O1	110.32 (16)
H1A—C1—H1B	109.5	N1—C6—C7	111.44 (14)
C4—C1—H1C	109.5	N1—C6—C6ⁱ	110.33 (13)
H1A—C1—H1C	109.5	C7—C6—C6ⁱ	110.22 (12)
H1B—C1—H1C	109.5	N1—C6—H6	108.3
C4—C2—H2A	109.5	C7—C6—H6	108.3
C4—C2—H2B	109.5	C6ⁱ—C6—H6	108.3
H2A—C2—H2B	109.5	C8—C7—C6	112.21 (16)
C4—C2—H2C	109.5	C8—C7—H7A	109.2
H2A—C2—H2C	109.5	C6—C7—H7A	109.2
H2B—C2—H2C	109.5	C8—C7—H7B	109.2
C4—C3—H3A	109.5	C6—C7—H7B	109.2
C4—C3—H3B	109.5	H7A—C7—H7B	107.9
H3A—C3—H3B	109.5	C7—C8—C8ⁱ	110.84 (14)
C4—C3—H3C	109.5	C7—C8—H8A	109.5
H3A—C3—H3C	109.5	C8ⁱ—C8—H8A	109.5
H3B—C3—H3C	109.5	C7—C8—H8B	109.5
O1—C4—C2	110.78 (16)	C8ⁱ—C8—H8B	109.5
O1—C4—C3	102.18 (15)	H8A—C8—H8B	108.1
C2—C4—C3	110.21 (17)	C5—N1—C6	121.99 (17)
O1—C4—C1	109.87 (16)	C5—N1—H99	121.2 (16)
C2—C4—C1	112.82 (16)	C6—N1—H99	116.1 (17)
C3—C4—C1	110.47 (18)	C5—O1—C4	120.55 (14)
O2—C5—N1	124.87 (19)

Symmetry code: (i) −x+1, y, −z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H99···O2ⁱⁱ	0.84 (2)	2.20 (3)	2.996 (2)	160 (2)

Symmetry code: (ii) x, y, z−1.

Acknowledgements

The authors thank the EPSRC for funding the crystallographic facilities.

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