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

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ISSN: 2056-9890

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

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)[link], was synthesized as part of our ongoing studies into enantioselective recognition (Botana et al., 2001[Botana, E., Ongeri, S., Arienzo, R., Demarcus, M., Frey, J. G., Piarulli, U., Potenza, D., Gennari, C. & Kilburn, J. D. (2001). Chem. Commun. 15, 1358-1359.]; Rossi et al., 2002[Rossi, S., Kyne, G. M., Turner, D. L., Wells, N. J. & Kilburn, J. D. (2002). Angew. Chem. Int. Ed. 41, 4233-4236.]; Kyne et al., 2001[Kyne, G. M., Light, M. E., Hursthouse, M. B., de Mendoza, J. & Kilburn, J. D. (2001). J. Chem. Soc. Perkin Trans. 1, pp. 1258-1263.]). 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[Beer, P. D., Gale, P. A. & Smith, D. K. (1999). Supramolecular Chemistry. Oxford University Press.]). 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)[link], 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.

[Scheme 1]

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[link]).

[Figure 1]
Figure 1
View of the structure of (I)[link], 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]
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]
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

  • Mr = 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

  • Dx = 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[Sheldrick, G. M. (2003). SADABS. Version 2.10. Bruker AXS Inc., Madison, Wisconsin, USA.])Tmin = 0.984, Tmax = 0.998

  • 3861 measured reflections

  • 1069 independent reflections

  • 966 reflections with I > 2σ(I)

  • Rint = 0.045

  • θmax = 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(Fo2) + (0.0274P)2 + 0.2768P] where P = (Fo2 + 2Fc2)/3

  • (Δ/σ)max = 0.006

  • Δρmax = 0.16 e Å−3

  • Δρmin = −0.15 e Å−3

  • Extinction correction: SHELXL97

  • Extinction coefficient: 0.018 (5)

Table 1
Hydrogen-bond geometry (Å, °)[link]

D—H⋯A D—H H⋯A DA 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 Uiso(H) = 1.5Ueq(C) for CH3, C—H = 0.99 Å and Uiso(H) = 1.2Ueq(C) for CH2, and C—H = 1.00 Å and Uiso(H) = 1.2Ueq(C) for CH. The single H atom on the N atom was freely refined.

Data collection: COLLECT (Hooft, 1998[Hooft, R. (1998). COLLECT. Nonius BV, Delft, The Netherlands.]); cell refinement: DENZO (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.]) and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990[Sheldrick, G. M. (1990). Acta Cryst. A46, 467-473.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXL97. University of Göttingen, Germany.]); molecular graphics: CAMERON (Watkin et al., 1993[Watkin, D. M., Pearce, L. & Prout, C. K. (1993). CAMERON. Chemical Crystallography Laboratory, University of Oxford, England.]); software used to prepare material for publication: WinGX (Farrugia, 1999[Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837-838.]).

Supporting information


Comment top

(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).

Experimental top

(1S,2S)-1,2-Diphenyl-1,2-ethylenediamine-L-tartrate salt (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 from 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%.

Refinement top

Freidel pairs were merged. All C-bound H atoms were located in a difference Fourier map, and were were placed in calculated positions and treated as riding on their parent atoms, with C—H = 0.98 Å and Uiso(H) = 1.5Ueq(C) for CH3, C—H = 0.99 Å and Uiso(H) = 1.2Ueq(C) for CH2, and C—H = 1.00 Å and Uiso(H) = 1.2Ueq(C) for CH. The single H atom on the N atom was freely refined.

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).

Figures top
[Figure 1] Fig. 1. View of the structure of (I), showing the atomic numbering scheme. Displacement ellipsoids for non-H atoms are drawn at the 35% probablity level, and H atoms are drawn with abitrary radii. [Symmetry code: (_1) −x + 1, y, −z.]
[Figure 2] Fig. 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 classic hydrogen bonds have been included.
[Figure 3] Fig. 3. A packing diagram viewed down c, showing the arrangement of the V-shaped molecules.
(1R*,2R*)-Di-tert-butyl N,N'-(cyclohexane-1,2-diyl)dicarbamate top
Crystal data top
C16H30N2O4F(000) = 344
Mr = 314.42Dx = 1.169 Mg m3
Monoclinic, C2Mo Kα radiation, λ = 0.71073 Å
Hall symbol: C 2yCell parameters from 982 reflections
a = 18.856 (4) Åθ = 2.9–27.5°
b = 9.3110 (19) ŵ = 0.08 mm1
c = 5.183 (1) ÅT = 120 K
β = 101.04 (3)°Slab, pale yellow
V = 893.1 (3) Å30.20 × 0.12 × 0.03 mm
Z = 2
Data collection top
Nonius KappaCCD
diffractometer
1069 independent reflections
Radiation source: Bruker Nonius FR591 Rotating Anode966 reflections with I > 2σ(I)
10cm confocal mirrors monochromatorRint = 0.045
Detector resolution: 9.091 pixels mm-1θmax = 27.5°, θmin = 4.0°
ϕ and ω scansh = 2324
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
k = 1212
Tmin = 0.984, Tmax = 0.998l = 66
3861 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)] = 0.035H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.078 w = 1/[σ2(Fo2) + (0.0274P)2 + 0.2768P]
where P = (Fo2 + 2Fc2)/3
S = 1.06(Δ/σ)max = 0.006
1069 reflectionsΔρmax = 0.16 e Å3
108 parametersΔρmin = 0.15 e Å3
1 restraintExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.018 (5)
Crystal data top
C16H30N2O4V = 893.1 (3) Å3
Mr = 314.42Z = 2
Monoclinic, C2Mo Kα radiation
a = 18.856 (4) ŵ = 0.08 mm1
b = 9.3110 (19) ÅT = 120 K
c = 5.183 (1) Å0.20 × 0.12 × 0.03 mm
β = 101.04 (3)°
Data collection top
Nonius KappaCCD
diffractometer
1069 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
966 reflections with I > 2σ(I)
Tmin = 0.984, Tmax = 0.998Rint = 0.045
3861 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0351 restraint
wR(F2) = 0.078H atoms treated by a mixture of independent and constrained refinement
S = 1.06Δρmax = 0.16 e Å3
1069 reflectionsΔρmin = 0.15 e Å3
108 parameters
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
xyzUiso*/Ueq
C10.37974 (12)0.2307 (2)0.5011 (4)0.0317 (5)
H1A0.41770.27020.41660.048*
H1B0.35790.30830.58700.048*
H1C0.40070.15930.63260.048*
C20.26751 (12)0.0748 (3)0.4139 (4)0.0297 (5)
H2A0.29300.00540.54090.045*
H2B0.23960.14060.50320.045*
H2C0.23480.02350.27440.045*
C30.28359 (12)0.2712 (3)0.1034 (4)0.0319 (5)
H3A0.24840.22330.03310.048*
H3B0.25860.33980.19810.048*
H3C0.31900.32220.02180.048*
C40.32203 (11)0.1598 (2)0.2946 (4)0.0249 (5)
C50.39673 (10)0.0463 (2)0.2217 (4)0.0237 (4)
C60.47084 (9)0.2357 (2)0.0855 (3)0.0211 (4)
H60.49550.23470.27430.025*
C70.42526 (11)0.3717 (2)0.0363 (4)0.0281 (5)
H7A0.39830.37150.14740.034*
H7B0.38960.37220.15370.034*
C80.47087 (12)0.5068 (2)0.0837 (4)0.0297 (5)
H8A0.49380.51280.27190.036*
H8B0.43950.59220.04000.036*
N10.42652 (9)0.1078 (2)0.0353 (3)0.0252 (4)
O10.35630 (8)0.06813 (17)0.1227 (2)0.0271 (4)
O20.40471 (8)0.08750 (17)0.4484 (3)0.0318 (4)
H990.4150 (12)0.083 (3)0.122 (5)0.028 (6)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0364 (12)0.0310 (12)0.0280 (11)0.0049 (10)0.0067 (9)0.0021 (9)
C20.0277 (11)0.0334 (11)0.0292 (11)0.0006 (10)0.0080 (8)0.0014 (10)
C30.0383 (12)0.0309 (11)0.0274 (11)0.0104 (11)0.0083 (8)0.0001 (9)
C40.0288 (10)0.0275 (11)0.0190 (10)0.0042 (9)0.0057 (7)0.0022 (8)
C50.0210 (10)0.0296 (11)0.0198 (10)0.0030 (9)0.0021 (7)0.0024 (8)
C60.0179 (9)0.0266 (10)0.0186 (10)0.0009 (9)0.0033 (7)0.0012 (8)
C70.0235 (10)0.0360 (12)0.0257 (10)0.0038 (10)0.0070 (8)0.0008 (9)
C80.0354 (12)0.0293 (12)0.0244 (11)0.0050 (10)0.0060 (9)0.0013 (9)
N10.0284 (9)0.0315 (10)0.0163 (9)0.0098 (8)0.0056 (7)0.0051 (7)
O10.0333 (8)0.0314 (8)0.0179 (7)0.0104 (7)0.0080 (6)0.0025 (6)
O20.0373 (8)0.0411 (9)0.0177 (7)0.0125 (8)0.0072 (6)0.0062 (6)
Geometric parameters (Å, º) top
C1—C41.523 (3)C5—N11.336 (3)
C1—H1A0.9800C5—O11.353 (2)
C1—H1B0.9800C6—N11.450 (3)
C1—H1C0.9800C6—C71.524 (3)
C2—C41.519 (3)C6—C6i1.539 (4)
C2—H2A0.9800C6—H61.0000
C2—H2B0.9800C7—C81.517 (3)
C2—H2C0.9800C7—H7A0.9900
C3—C41.519 (3)C7—H7B0.9900
C3—H3A0.9800C8—C8i1.525 (4)
C3—H3B0.9800C8—H8A0.9900
C3—H3C0.9800C8—H8B0.9900
C4—O11.470 (2)N1—H990.84 (2)
C5—O21.218 (2)
C4—C1—H1A109.5O2—C5—O1124.81 (18)
C4—C1—H1B109.5N1—C5—O1110.32 (16)
H1A—C1—H1B109.5N1—C6—C7111.44 (14)
C4—C1—H1C109.5N1—C6—C6i110.33 (13)
H1A—C1—H1C109.5C7—C6—C6i110.22 (12)
H1B—C1—H1C109.5N1—C6—H6108.3
C4—C2—H2A109.5C7—C6—H6108.3
C4—C2—H2B109.5C6i—C6—H6108.3
H2A—C2—H2B109.5C8—C7—C6112.21 (16)
C4—C2—H2C109.5C8—C7—H7A109.2
H2A—C2—H2C109.5C6—C7—H7A109.2
H2B—C2—H2C109.5C8—C7—H7B109.2
C4—C3—H3A109.5C6—C7—H7B109.2
C4—C3—H3B109.5H7A—C7—H7B107.9
H3A—C3—H3B109.5C7—C8—C8i110.84 (14)
C4—C3—H3C109.5C7—C8—H8A109.5
H3A—C3—H3C109.5C8i—C8—H8A109.5
H3B—C3—H3C109.5C7—C8—H8B109.5
O1—C4—C2110.78 (16)C8i—C8—H8B109.5
O1—C4—C3102.18 (15)H8A—C8—H8B108.1
C2—C4—C3110.21 (17)C5—N1—C6121.99 (17)
O1—C4—C1109.87 (16)C5—N1—H99121.2 (16)
C2—C4—C1112.82 (16)C6—N1—H99116.1 (17)
C3—C4—C1110.47 (18)C5—O1—C4120.55 (14)
O2—C5—N1124.87 (19)
Symmetry code: (i) x+1, y, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H99···O2ii0.84 (2)2.20 (3)2.996 (2)160 (2)
Symmetry code: (ii) x, y, z1.

Experimental details

Crystal data
Chemical formulaC16H30N2O4
Mr314.42
Crystal system, space groupMonoclinic, C2
Temperature (K)120
a, b, c (Å)18.856 (4), 9.3110 (19), 5.183 (1)
β (°) 101.04 (3)
V3)893.1 (3)
Z2
Radiation typeMo Kα
µ (mm1)0.08
Crystal size (mm)0.20 × 0.12 × 0.03
Data collection
DiffractometerNonius KappaCCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 2003)
Tmin, Tmax0.984, 0.998
No. of measured, independent and
observed [I > 2σ(I)] reflections
3861, 1069, 966
Rint0.045
(sin θ/λ)max1)0.650
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.035, 0.078, 1.06
No. of reflections1069
No. of parameters108
No. of restraints1
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.16, 0.15

Computer programs: COLLECT (Hooft, 1998), DENZO (Otwinowski & Minor, 1997) and COLLECT, DENZO and COLLECT, SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), CAMERON (Watkin et al., 1993), WinGX (Farrugia, 1999).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H99···O2i0.84 (2)2.20 (3)2.996 (2)160 (2)
Symmetry code: (i) x, y, z1.
 

Acknowledgements

The authors thank the EPSRC for funding the crystallographic facilities.

References

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