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Acta Cryst. (2008). E64, o687    [ doi:10.1107/S1600536808006119 ]

(1R,2R)-N,N'-Dimethylcyclohexane-1,2-diamine

C. Strohmann, V. H. Gessner, A. Damme, S. Koller and C. Däschlein

Abstract top

The molecule of the title compound, C8H18N2, possesses C2 symmetry. Owing to its stereochemistry, it is used in the synthesis of chiral ligands and metal complexes for asymmetric synthesis. The cyclohexane ring shows a chair conformation with the amino groups in equatorial positions. Contrary to the literature, the title compound is not a liquid, but a crystalline solid at room temperature (293 K). The absolute configuration is assigned from the synthesis.

Comment top

Due to their strong coordination ability diamine bases have become powerful agents in various fields of chemistry e.g. for the deaggregation of organolithium compounds or the coordination of transition metals. Especially chiral amines have attracted special attention in asymmetric synthesis. Thereby, (1R,2R)-N,N'-dimethylcyclohexane-1,2-diamine is an important chiral amine, which serves as a starting material for the synthesis of numerous diamine bases with a cyclohexane framework. The amine crystallizes at room temperature as colourless needles in the orthorhombic crystal system, space group P212121. The asymmetric unit contains one molecule of the C2 symmetric amine (see figure 1).

In the unit cell molecules are interconnected via hydrogen bonding to give infinite layers (see figure 2). H atoms (H1N) are arranged in direction to the nitrogen atom (N2) of an adjacent molecule (N1—HN1—N2' angle: 166 (3)°). However, the long N1—N2' distance of 3.250 (4) Å and the short N1—HN1 distance of 0.91 (4) Å indicate weak N–H···N hydrogen bonds.

Related literature top

The synthesis of the title compound is described by Kizirian et al. (2005). For related literature, see: Larrox and Jacobsen (1994); Cole et al. (2005); Seebach et al. (1977); Strohmann & Gessner (2007); Strohmann et al. (2003, 2004); Strohmann, Däschlein & Auer (2006); Strohmann, Dilsky & Strohfeldt (2006); Strohmmann & Gessner (2007a,b).

Experimental top

Treatment of the enantiomerically pure (R,R)-1,2-diammoniumcyclohexane mono-(+)-tartrate with two equivalents of ethylchloroformate in the presence of a stochiometric amount of NaOH resulted in the formation of diethyl-(1R,2R)-cyclohexane-1,2-diyldicarbamat. Subsequent reduction with an excess of LiAlH4 gave colourless crystals of the title compound during bulb-to-bulb destillation. Contrary to a formerly published synthesis, (1R,2R)-N,N'-diemthylcyclohexane-1,2-diamine is not liquid but a highly hygroscopic crystalline solid.

1H-NMR (500.1 MHz, CDCl3): 0.86–0.94 (m, 2H; CH2CHN), 1.13–1.19 (m, 2H; CH2CH2CHN), 1.61–1.67 (m, 2H; CH2CH2CHN), 1.68–1.75 (br, 2H, NH), 1.93–2.00 (m, 2H; CH2CHN), 2.02–2.06 (m, 2H; CHNCHN), 2.33 (s, 6H; NCH3).

13C-NMR (100.6 MHz, CDCl3): 25.0 (CH2CH2CHN), 30.8 (CH2CHN), 33.7 (CH3), 63.2 (CHN).

Refinement top

Refinement was accomplished by full-matrix least-squares methods (based on Fo2, SHELXL97); anisotropic thermal parameters for all non-H atoms in the final cycles; the H atoms were refined on a riding model in their ideal geometric positions, except for H(1 N) and H(2 N), which were refined independently.

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT-Plus (Bruker, 1999); data reduction: SAINT-Plus (Bruker, 1999); program(s) used to solve structure: SHELXS90 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1999); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. ORTEP plot of the molecular structure of (1R,2R)-N,N'-diemthylcyclohexane-1,2-diamine. Thermal ellipsoids are drawn at the 50% probability level.
[Figure 2] Fig. 2. ORTEP plot of the unit cell.
[Figure 3] Fig. 3. Display of the hydrogen bonding.
(1R,2R)-N,N'-Dimethylcyclohexane-1,2-diamine top
Crystal data top
C8H18N2F000 = 320
Mr = 142.24Dx = 1.038 Mg m−3
Orthorhombic, P212121Melting point: 313 K
Hall symbol: P 2ac 2abMo Kα radiation
λ = 0.71073 Å
a = 7.552 (4) Åθ = 2.8–25.0º
b = 8.521 (5) ŵ = 0.06 mm−1
c = 14.142 (8) ÅT = 173 (2) K
V = 910.0 (8) Å3Needle, colourless
Z = 40.40 × 0.10 × 0.10 mm
Data collection top
Bruker APEXCCD
diffractometer		953 independent reflections
Radiation source: fine-focus sealed tube784 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.050
T = 173(2) Kθmax = 25.0º
ω scansθmin = 2.8º
Absorption correction: multi-scan
(SADABS; Bruker, 1999)		h = −8→8
Tmin = 0.912, Tmax = 0.982k = −10→9
4816 measured reflectionsl = −16→16
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)] = 0.051H atoms treated by a mixture of
independent and constrained refinement
wR(F2) = 0.111  w = 1/[σ2(Fo2) + (0.0405P)2 + 0.258P]
where P = (Fo2 + 2Fc2)/3
S = 1.08(Δ/σ)max < 0.001
953 reflectionsΔρmax = 0.12 e Å−3
101 parametersΔρmin = −0.11 e Å−3
Primary atom site location: structure-invariant direct methodsExtinction correction: none
Crystal data top
C8H18N2V = 910.0 (8) Å3
Mr = 142.24Z = 4
Orthorhombic, P212121Mo Kα
a = 7.552 (4) ŵ = 0.06 mm−1
b = 8.521 (5) ÅT = 173 (2) K
c = 14.142 (8) Å0.40 × 0.10 × 0.10 mm
Data collection top
Bruker APEXCCD
diffractometer		953 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 1999)		784 reflections with I > 2σ(I)
Tmin = 0.912, Tmax = 0.982Rint = 0.050
4816 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.051Δρmax = 0.12 e Å−3
wR(F2) = 0.111Δρmin = −0.11 e Å−3
S = 1.08Absolute structure: ?
953 reflectionsFlack parameter: ?
101 parametersRogers parameter: ?
H atoms treated by a mixture of
independent and constrained refinement
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
C10.8581 (4)0.3857 (3)0.28989 (19)0.0346 (7)
H10.87020.50000.30460.042*
C20.6814 (4)0.3316 (4)0.3294 (2)0.0477 (9)
H2A0.67850.35250.39820.057*
H2B0.67030.21680.32020.057*
C30.5242 (4)0.4129 (5)0.2827 (3)0.0608 (11)
H3A0.41280.36630.30670.073*
H3B0.52470.52560.29990.073*
C40.5304 (4)0.3970 (4)0.1764 (3)0.0528 (10)
H4A0.51310.28570.15860.063*
H4B0.43330.45900.14790.063*
C50.7059 (4)0.4540 (4)0.1385 (2)0.0458 (9)
H5A0.71740.56790.15090.055*
H5B0.70910.43810.06910.055*
C60.8605 (4)0.3685 (3)0.18321 (18)0.0331 (7)
H60.85140.25450.16710.040*
C71.0546 (5)0.3573 (4)0.4252 (2)0.0581 (10)
H7A1.08070.46990.42500.087*
H7B1.15830.29940.44800.087*
H7C0.95370.33670.46700.087*
C81.0664 (5)0.3767 (5)0.0508 (2)0.0644 (11)
H8A1.04920.26290.04650.097*
H8B1.18940.40250.03500.097*
H8C0.98660.42960.00650.097*
N11.0117 (3)0.3064 (4)0.32977 (18)0.0389 (7)
H1N0.985 (4)0.203 (4)0.329 (2)0.056 (10)*
N21.0282 (4)0.4287 (3)0.14644 (19)0.0413 (7)
H2N1.109 (4)0.391 (4)0.193 (2)0.045 (9)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0385 (17)0.0216 (15)0.0438 (17)0.0043 (16)0.0006 (14)0.0013 (13)
C20.044 (2)0.0420 (19)0.057 (2)0.0050 (17)0.0110 (17)0.0051 (17)
C30.039 (2)0.053 (2)0.090 (3)0.0029 (19)0.010 (2)0.007 (2)
C40.0335 (19)0.0403 (19)0.085 (3)−0.0023 (17)−0.0126 (19)0.0081 (19)
C50.046 (2)0.0355 (19)0.056 (2)−0.0032 (17)−0.0131 (16)0.0054 (16)
C60.0341 (16)0.0251 (16)0.0400 (17)−0.0025 (15)−0.0054 (14)−0.0008 (13)
C70.068 (2)0.055 (2)0.052 (2)0.010 (2)−0.0109 (18)−0.0046 (18)
C80.057 (2)0.085 (3)0.052 (2)−0.008 (2)0.0120 (18)0.005 (2)
N10.0389 (15)0.0388 (16)0.0390 (15)0.0029 (14)−0.0033 (13)0.0002 (13)
N20.0370 (16)0.0514 (18)0.0355 (15)−0.0048 (14)0.0004 (13)0.0048 (13)
Geometric parameters (Å, °) top
C1—N11.455 (4)C5—H5A0.9900
C1—C61.516 (4)C5—H5B0.9900
C1—C21.519 (4)C6—N21.462 (4)
C1—H11.0000C6—H61.0000
C2—C31.525 (4)C7—N11.454 (4)
C2—H2A0.9900C7—H7A0.9800
C2—H2B0.9900C7—H7B0.9800
C3—C41.511 (5)C7—H7C0.9800
C3—H3A0.9900C8—N21.452 (4)
C3—H3B0.9900C8—H8A0.9800
C4—C51.510 (4)C8—H8B0.9800
C4—H4A0.9900C8—H8C0.9800
C4—H4B0.9900N1—H1N0.91 (4)
C5—C61.515 (4)N2—H2N0.96 (3)
N1—C1—C6109.4 (2)C4—C5—H5B109.2
N1—C1—C2114.6 (2)C6—C5—H5B109.2
C6—C1—C2110.3 (3)H5A—C5—H5B107.9
N1—C1—H1107.4N2—C6—C5110.5 (2)
C6—C1—H1107.4N2—C6—C1109.3 (2)
C2—C1—H1107.4C5—C6—C1111.1 (3)
C1—C2—C3112.8 (3)N2—C6—H6108.6
C1—C2—H2A109.0C5—C6—H6108.6
C3—C2—H2A109.0C1—C6—H6108.6
C1—C2—H2B109.0N1—C7—H7A109.5
C3—C2—H2B109.0N1—C7—H7B109.5
H2A—C2—H2B107.8H7A—C7—H7B109.5
C4—C3—C2111.4 (3)N1—C7—H7C109.5
C4—C3—H3A109.3H7A—C7—H7C109.5
C2—C3—H3A109.3H7B—C7—H7C109.5
C4—C3—H3B109.3N2—C8—H8A109.5
C2—C3—H3B109.3N2—C8—H8B109.5
H3A—C3—H3B108.0H8A—C8—H8B109.5
C5—C4—C3110.6 (3)N2—C8—H8C109.5
C5—C4—H4A109.5H8A—C8—H8C109.5
C3—C4—H4A109.5H8B—C8—H8C109.5
C5—C4—H4B109.5C7—N1—C1113.5 (2)
C3—C4—H4B109.5C7—N1—H1N111 (2)
H4A—C4—H4B108.1C1—N1—H1N106 (2)
C4—C5—C6111.9 (3)C8—N2—C6113.4 (3)
C4—C5—H5A109.2C8—N2—H2N114.6 (19)
C6—C5—H5A109.2C6—N2—H2N100.9 (19)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N1—H1N···N2i0.91 (4)2.36 (4)3.250 (4)166 (3)
Symmetry codes: (i) −x+2, y−1/2, −z+1/2.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N1—H1N···N2i0.91 (4)2.36 (4)3.250 (4)166 (3)
Symmetry codes: (i) −x+2, y−1/2, −z+1/2.
Acknowledgements top

We are grateful to the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie(FCI). VHG thanks the FCI, and CD the Studienstiftung des deutschen Volkesfor a doctoral scholarship.

references
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