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Acta Cryst. (2009). E65, o956    [ doi:10.1107/S160053680901109X ]

(1R,2R)-N,N'-Diisobutyl-N,N'-dimethylcyclohexane-1,2-diamine

P. K. Eckert, V. H. Gessner and C. Strohmann

Abstract top

The title compound, C16H34N2, is a chiral diamine with fixed R configuration at both stereogenic carbon centres of the cyclohexane backbone. Due to their different substituents, the two N atoms also become stereogenic. In the crystal structure, the configuration at one of the two nitrogen centres is fixed, with the free electron pair pointing inward and the isobutyl group in a trans position towards the cyclohexane backbone resulting in an R configuration. The isobutyl group at the second N atom, however, is disordered with 75% S configuration and 25% R configuration. In both cases, the isobutyl group is arranged in a trans position towards the cyclohexane backbone.

Comment top

In preparative chemistry, chiral nitrogen ligands such as (1R,2R)-N,N,N',N'-tetramethylcyclohexane-1,2-diamine [(R,R)-TMCDA] and its derivatives are often used to enhance the stereoselectivity of deprotonation or addition reactions by coordinating to organolithium reagents (Kizirian, 2008). In the case of the cyclohexanediamine ligands, derivatives with three different substituents at the nitrogen centres revealed to be more efficient than their symmetric analogues (Kizirian et al., 2003; Stead et al., 2008).

The title compound represents the crystal structure of such an uncoordinated (R,R)-TMCDA derivative (for related crystal structures, see: Strohmann & Gessner, 2007a,b; Strohmann & Gessner, 2008; Strohmann et al. et al., 2008b; Strohmann et al., 2008a). (1R,2R)-N,N'-diisobutyl-N, N'-dimethylcyclohexane-1,2-diamine (1) (Fig. 1), crystallizes at -78 °C in the orthorhombic crystal system, space group P212121. The asymmetric unit contains one molecule of the chiral diamine. The configuration at one of the two nitrogen centres is fixed with the free electron pair pointing inward and the isobutyl group arranged in a trans-position towards the cyclohexane backbone. The second nitrogen centre, however, can be described by a model that has the free electron pair pointing outwards in 75% of all molecules and inwards in the others.

Related literature top

The synthesis of the title compound is described by Kizirian et al. (2003). For the crystal structure of the related molecule (1R,2R)-N,N'- dimethylcyclohexane-1,2-diamine, see Strohmann et al. (2008b). Crystal structures of (1R,2R)-N,N'- tetramethylcyclohexane-1,2-diamine coordinated to lithium organyls are described by Strohmann & Gessner (2007a) and Strohmann & Gessner (2008). Other related diamines coordinated to lithium organyls are specified by Strohmann & Gessner (2007b) and Strohmann et al. (2008a). The use of chiral nitrogen ligands to enhance the stereoselectivity of deprotonation or addition reactions is discussed by Kizirian (2008) and Stead et al. (2008).

Experimental top

The title compound (100 mg, 0.39 mmol) was diluted in n-pentane (2 ml). After cooling to -78 °C, clear crystals suitable for single-crystal x-ray studies were obtained. For synthesis of the title compound, see Kizirian et al. (2003).

Refinement top

H atoms were refined using a riding model in their ideal geometric positions with Uiso(H) = 1.5Ueq(C) for methyl H atoms and Uiso(H) = 1.2Ueq(C) for all other H atoms. H14 was located from the Fourier map and refined and its coordinates were refined freely yielding a C—H distance of 1.03 (3) Å. The Friedel pairs were not merged and the Flack parameter (Flack, 1983) yielded an indeterminate value with large uncertainty (1(4)). The following distances were restrained using DFIX: C13b—N2 and N2—C13a at 1.43 Å, C14—C16b, C14—16a, C14—C15a and C14—C15b at 1.52 Å. For the description of the disorder, a splitting model was used which had the free electron pair at the nitrogen centre pointing outwards in 75% of all molecules and inwards in the others. Absolute structure: not determined in the present model. Absolute configuration: known from starting material.

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: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound with thermal ellipsoids drawn at the 50% probability level.
(1R,2R)-N,N'-Diisobutyl-N,N'- dimethylcyclohexane-1,2-diamine top
Crystal data top
C16H34N2F(000) = 576
Mr = 254.45Dx = 0.991 Mg m−3
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P2ac 2abCell parameters from 999 reflections
a = 10.4693 (15) Åθ = 2.3–25°
b = 10.8013 (16) ŵ = 0.06 mm−1
c = 15.077 (2) ÅT = 173 K
V = 1705.0 (4) Å3Plates, colourless
Z = 40.40 × 0.40 × 0.20 mm
Data collection top
Bruker SMART APEX CCD
diffractometer		3004 independent reflections
Radiation source: fine-focus sealed tube2730 reflections with I > 2σ(I)
graphiteRint = 0.051
ω scansθmax = 25.0°, θmin = 2.3°
Absorption correction: multi-scan
(SADABS; Bruker, 1999)		h = −12→12
Tmin = 0.977, Tmax = 0.989k = −12→12
20171 measured reflectionsl = −17→17
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.056Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.149H atoms treated by a mixture of independent and constrained refinement
S = 1.06 w = 1/[σ2(Fo2) + (0.0787P)2 + 0.3166P]
where P = (Fo2 + 2Fc2)/3
3004 reflections(Δ/σ)max < 0.001
202 parametersΔρmax = 0.20 e Å−3
6 restraintsΔρmin = −0.13 e Å−3
Crystal data top
C16H34N2V = 1705.0 (4) Å3
Mr = 254.45Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 10.4693 (15) ŵ = 0.06 mm−1
b = 10.8013 (16) ÅT = 173 K
c = 15.077 (2) Å0.40 × 0.40 × 0.20 mm
Data collection top
Bruker SMART APEX CCD
diffractometer		3004 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 1999)		2730 reflections with I > 2σ(I)
Tmin = 0.977, Tmax = 0.989Rint = 0.051
20171 measured reflectionsθmax = 25.0°
Refinement top
R[F2 > 2σ(F2)] = 0.056H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.149Δρmax = 0.20 e Å−3
S = 1.06Δρmin = −0.13 e Å−3
3004 reflectionsAbsolute structure: ?
202 parametersFlack parameter: ?
6 restraintsRogers parameter: ?
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*/UeqOcc. (<1)
C10.7243 (2)0.2944 (2)0.79640 (18)0.0615 (6)
H1A0.66950.32570.74870.092*
H1B0.81410.30690.78040.092*
H1C0.70550.33900.85140.092*
C20.5745 (2)0.1385 (2)0.84275 (17)0.0589 (6)
H2A0.56300.18500.89880.071*
H2B0.56830.04930.85700.071*
C30.4646 (2)0.1725 (2)0.77945 (15)0.0546 (6)
H30.46480.26430.77040.065*
C40.3389 (2)0.1358 (3)0.8223 (2)0.0727 (8)
H4A0.26820.15720.78250.109*
H4B0.32880.18020.87850.109*
H4C0.33850.04640.83340.109*
C50.4814 (3)0.1104 (3)0.69055 (19)0.0778 (8)
H5A0.48850.02070.69900.117*
H5B0.55920.14150.66210.117*
H5C0.40750.12860.65290.117*
C60.7989 (2)0.0998 (2)0.86174 (14)0.0489 (5)
H60.76550.01450.87330.059*
C70.8261 (2)0.1571 (2)0.95317 (15)0.0559 (6)
H7A0.86330.24060.94520.067*
H7B0.74490.16620.98610.067*
C80.9177 (2)0.0778 (3)1.00701 (16)0.0629 (6)
H8A0.93560.11871.06440.075*
H8B0.8778−0.00351.01940.075*
C91.0415 (3)0.0585 (3)0.95720 (17)0.0649 (7)
H9A1.09740.00200.99130.078*
H9B1.08620.13880.95090.078*
C101.0166 (2)0.0039 (2)0.86573 (17)0.0597 (6)
H10A0.9798−0.08000.87260.072*
H10B1.0989−0.00450.83390.072*
C110.9259 (2)0.0829 (2)0.81027 (15)0.0498 (5)
H110.96560.16670.80480.060*
C120.8408 (3)−0.0772 (2)0.71239 (16)0.0619 (6)
H12A0.7509−0.05850.72450.093*
H12B0.8714−0.13920.75480.093*
H12C0.8492−0.10970.65200.093*
C140.9642 (3)0.0817 (2)0.56237 (16)0.0668 (7)
H140.931 (3)−0.003 (3)0.5418 (19)0.075 (8)*
C13A0.8956 (3)0.1169 (3)0.64982 (18)0.0542 (7)0.75
H13C0.92560.19980.66860.065*0.75
H13D0.80280.12310.63800.065*0.75
C15A1.1073 (3)0.0796 (6)0.5758 (4)0.1065 (18)0.75
H15D1.13690.16250.59240.160*0.75
H15E1.14920.05410.52060.160*0.75
H15F1.12870.02080.62300.160*0.75
C16A0.9211 (5)0.1727 (3)0.4920 (3)0.0825 (12)0.75
H16D0.82840.16630.48420.124*0.75
H16E0.96370.15350.43570.124*0.75
H16F0.94320.25700.51040.124*0.75
C13B1.0029 (8)0.0830 (10)0.6582 (5)0.062 (3)0.25
H13A1.08420.03690.66370.074*0.25
H13B1.02040.16990.67510.074*0.25
C15B1.0898 (9)0.1100 (18)0.5153 (9)0.102 (5)0.25
H15A1.07410.12020.45170.153*0.25
H15B1.14970.04160.52470.153*0.25
H15C1.12630.18650.53940.153*0.25
C16B0.8646 (9)0.1787 (9)0.5399 (8)0.079 (4)0.25
H16A0.90040.26140.54970.118*0.25
H16B0.78960.16730.57790.118*0.25
H16C0.83940.17010.47760.118*0.25
N10.70037 (17)0.16326 (17)0.80918 (12)0.0488 (4)
N20.9148 (2)0.03281 (19)0.72094 (12)0.0610 (6)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0625 (14)0.0513 (13)0.0708 (16)0.0042 (11)0.0025 (13)0.0042 (12)
C20.0647 (14)0.0613 (14)0.0507 (13)−0.0004 (11)0.0043 (11)−0.0009 (11)
C30.0584 (13)0.0525 (12)0.0528 (13)0.0063 (11)−0.0044 (11)−0.0018 (11)
C40.0608 (14)0.0777 (17)0.0795 (19)0.0068 (13)0.0026 (14)−0.0061 (15)
C50.0804 (18)0.096 (2)0.0568 (15)−0.0007 (16)−0.0078 (15)−0.0057 (15)
C60.0569 (12)0.0472 (12)0.0425 (11)−0.0058 (10)0.0003 (10)0.0022 (9)
C70.0600 (13)0.0661 (14)0.0417 (12)−0.0017 (12)0.0012 (10)−0.0021 (11)
C80.0668 (15)0.0772 (16)0.0447 (13)−0.0073 (14)−0.0073 (12)0.0019 (12)
C90.0615 (14)0.0754 (17)0.0577 (14)−0.0009 (13)−0.0100 (12)0.0024 (13)
C100.0534 (13)0.0625 (15)0.0633 (15)0.0003 (11)−0.0009 (12)−0.0041 (12)
C110.0545 (12)0.0490 (11)0.0458 (12)−0.0074 (10)0.0008 (10)−0.0032 (10)
C120.0734 (16)0.0575 (14)0.0548 (14)−0.0028 (12)−0.0042 (12)−0.0110 (12)
C140.093 (2)0.0611 (15)0.0467 (13)−0.0051 (14)0.0091 (13)−0.0048 (12)
C13A0.0574 (18)0.0569 (17)0.0483 (18)−0.0011 (14)0.0007 (14)−0.0032 (14)
C15A0.093 (4)0.144 (5)0.083 (3)0.033 (3)0.031 (3)0.022 (4)
C16A0.125 (4)0.077 (2)0.045 (2)−0.008 (3)0.001 (2)−0.0032 (19)
C13B0.040 (5)0.080 (7)0.065 (6)−0.012 (4)0.009 (4)−0.019 (5)
C15B0.074 (8)0.159 (16)0.072 (9)−0.006 (9)−0.008 (7)−0.035 (10)
C16B0.081 (8)0.112 (10)0.044 (6)−0.024 (7)−0.002 (6)0.001 (7)
N10.0529 (10)0.0485 (10)0.0449 (10)−0.0022 (8)−0.0001 (8)0.0034 (8)
N20.0701 (13)0.0672 (12)0.0457 (11)−0.0163 (10)0.0073 (10)−0.0078 (9)
Geometric parameters (Å, °) top
C1—N11.451 (3)C10—H10B0.99
C1—H1A0.98C11—N21.456 (3)
C1—H1B0.98C11—H111
C1—H1C0.98C12—N21.425 (3)
C2—N11.437 (3)C12—H12A0.98
C2—C31.539 (3)C12—H12B0.98
C2—H2A0.99C12—H12C0.98
C2—H2B0.99C14—C13B1.500 (9)
C3—C51.509 (4)C14—C15A1.512 (3)
C3—C41.519 (3)C14—C16A1.516 (3)
C3—H31C14—C16B1.517 (3)
C4—H4A0.98C14—C15B1.525 (3)
C4—H4B0.98C14—C13A1.549 (4)
C4—H4C0.98C14—H141.03 (3)
C5—H5A0.98C13A—N21.4196 (18)
C5—H5B0.98C13A—H13C0.99
C5—H5C0.98C13A—H13D0.99
C6—N11.470 (3)C15A—H15D0.98
C6—C71.538 (3)C15A—H15E0.98
C6—C111.550 (3)C15A—H15F0.98
C6—H61C16A—H16D0.98
C7—C81.521 (3)C16A—H16E0.98
C7—H7A0.99C16A—H16F0.98
C7—H7B0.99C13B—N21.428 (2)
C8—C91.512 (4)C13B—H13A0.99
C8—H8A0.99C13B—H13B0.99
C8—H8B0.99C15B—H15A0.98
C9—C101.522 (4)C15B—H15B0.98
C9—H9A0.99C15B—H15C0.98
C9—H9B0.99C16B—H16A0.98
C10—C111.527 (3)C16B—H16B0.98
C10—H10A0.99C16B—H16C0.98
N1—C1—H1A109.5C10—C11—H11107
N1—C1—H1B109.5C6—C11—H11107
H1A—C1—H1B109.5N2—C12—H12A109.5
N1—C1—H1C109.5N2—C12—H12B109.5
H1A—C1—H1C109.5H12A—C12—H12B109.5
H1B—C1—H1C109.5N2—C12—H12C109.5
N1—C2—C3115.0 (2)H12A—C12—H12C109.5
N1—C2—H2A108.5H12B—C12—H12C109.5
C3—C2—H2A108.5C15A—C14—C16A113.5 (4)
N1—C2—H2B108.5C13B—C14—C16B113.2 (7)
C3—C2—H2B108.5C13B—C14—C15B102.3 (6)
H2A—C2—H2B107.5C16B—C14—C15B110.5 (9)
C5—C3—C4111.3 (2)C15A—C14—C13A110.4 (3)
C5—C3—C2110.9 (2)C16A—C14—C13A107.4 (3)
C4—C3—C2108.8 (2)C13B—C14—H14113.1 (16)
C5—C3—H3108.6C15A—C14—H14111.5 (17)
C4—C3—H3108.6C16A—C14—H14105.3 (16)
C2—C3—H3108.6C16B—C14—H14108.2 (17)
C3—C4—H4A109.5C15B—C14—H14109.5 (18)
C3—C4—H4B109.5C13A—C14—H14108.5 (17)
H4A—C4—H4B109.5N2—C13A—C14114.8 (2)
C3—C4—H4C109.5N2—C13A—H13C108.6
H4A—C4—H4C109.5C14—C13A—H13C108.6
H4B—C4—H4C109.5N2—C13A—H13D108.6
C3—C5—H5A109.5C14—C13A—H13D108.6
C3—C5—H5B109.5H13C—C13A—H13D107.5
H5A—C5—H5B109.5C14—C15A—H15D109.5
C3—C5—H5C109.5C14—C15A—H15E109.5
H5A—C5—H5C109.5H15D—C15A—H15E109.5
H5B—C5—H5C109.5C14—C15A—H15F109.5
N1—C6—C7115.18 (19)H15D—C15A—H15F109.5
N1—C6—C11112.73 (17)H15E—C15A—H15F109.5
C7—C6—C11109.68 (18)C14—C16A—H16D109.5
N1—C6—H6106.2C14—C16A—H16E109.5
C7—C6—H6106.2H16D—C16A—H16E109.5
C11—C6—H6106.2C14—C16A—H16F109.5
C8—C7—C6111.6 (2)H16D—C16A—H16F109.5
C8—C7—H7A109.3H16E—C16A—H16F109.5
C6—C7—H7A109.3N2—C13B—C14117.4 (6)
C8—C7—H7B109.3N2—C13B—H13A108
C6—C7—H7B109.3C14—C13B—H13A108
H7A—C7—H7B108N2—C13B—H13B108
C9—C8—C7110.6 (2)C14—C13B—H13B108
C9—C8—H8A109.5H13A—C13B—H13B107.2
C7—C8—H8A109.5C14—C15B—H15A109.5
C9—C8—H8B109.5C14—C15B—H15B109.5
C7—C8—H8B109.5H15A—C15B—H15B109.5
H8A—C8—H8B108.1C14—C15B—H15C109.5
C8—C9—C10110.9 (2)H15A—C15B—H15C109.5
C8—C9—H9A109.5H15B—C15B—H15C109.5
C10—C9—H9A109.5C14—C16B—H16A109.5
C8—C9—H9B109.5C14—C16B—H16B109.5
C10—C9—H9B109.5H16A—C16B—H16B109.5
H9A—C9—H9B108C14—C16B—H16C109.5
C9—C10—C11112.7 (2)H16A—C16B—H16C109.5
C9—C10—H10A109.1H16B—C16B—H16C109.5
C11—C10—H10A109.1C2—N1—C1112.73 (19)
C9—C10—H10B109.1C2—N1—C6111.51 (17)
C11—C10—H10B109.1C1—N1—C6113.93 (18)
H10A—C10—H10B107.8C13A—N2—C12112.9 (2)
N2—C11—C10110.38 (19)C12—N2—C13B127.4 (5)
N2—C11—C6116.00 (19)C13A—N2—C11118.2 (2)
C10—C11—C6108.98 (18)C12—N2—C11115.92 (18)
N2—C11—H11107C13B—N2—C11114.9 (4)
Acknowledgements top

The authors thank the Fonds der Chemischen Industrie (FCI) and the Deutsche Forschungsgemeinschaft (DFG) for financial support.

references
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