2,2′-[(2S*,6R*)-Piperidine-2,6-di­yl]­di­pro­pan-2-ol

Guillaume Journot; Reinhard Neier; Helen Stoeckli-Evans

doi:10.1107/S1600536812005879

. 2012 Feb 24;68(Pt 3):o857. doi: 10.1107/S1600536812005879

2,2′-[(2S,6R)-Piperidine-2,6-diyl]dipropan-2-ol

Guillaume Journot ^a, Reinhard Neier ^a,^*, Helen Stoeckli-Evans ^b

PMCID: PMC3297911 PMID: 22412714

Abstract

In the title compound, C₁₁H₂₃NO₂, the piperidine ring has a chair conformation. The two hydroxy H atoms are disordered over two positions with fixed occupancy ratios of 0.57:0.43 and 0.63:0.37. In the molecule, there are two short N—H⋯O interactions. In the crystal, four symmetry-related molecules are linked by O—H⋯O hydrogen bonds to form a cage-like arrangement, centered about the point of intersection of three twofold axes. These cages stack along the [100] direction.

Related literature

For literature on ligands of the pincer-type family, see: van Koten (1989 ▶); Albrecht & van Koten (2001 ▶). For metal complexes of such pincer ligands, see: Hofmeier & Schubert (2004 ▶); Li et al. (2007 ▶). For the synthesis of the starting material 2,2′-(pyridine-2,6-diyl)dipropan-2-ol, see: Klein et al. (2009 ▶). For an example of the transformation of bis-benzylic alcohols of 2,6-disubstituted pyridines, see: Klein et al. (2009 ▶). For the crystal structure of cis-(piperidine-2,6-diyl)dimethanol, see: Hartung et al. (2007 ▶).

Experimental

Crystal data

C₁₁H₂₃NO₂
M _r = 201.30
Orthorhombic,
a = 12.0713 (9) Å
b = 23.4762 (10) Å
c = 34.496 (2) Å
V = 9775.8 (10) Å³
Z = 32
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 173 K
0.45 × 0.45 × 0.40 mm

Data collection

Stoe IPDS 2 diffractometer
Absorption correction: multi-scan (MULscanABS in PLATON; Spek, 2009 ▶) T _min = 0.911, T _max = 1.000
32226 measured reflections
2319 independent reflections
1499 reflections with I > 2σ(I)
R _int = 0.135

Refinement

R[F ² > 2σ(F ²)] = 0.086
wR(F ²) = 0.146
S = 1.16
2319 reflections
135 parameters
4 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.16 e Å⁻³
Δρ_min = −0.15 e Å⁻³

Data collection: X-AREA (Stoe & Cie, 2009 ▶); cell refinement: X-AREA; data reduction: X-RED32 (Stoe & Cie, 2009 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2009 ▶) and Mercury (Macrae et al., 2008 ▶); software used to prepare material for publication: SHELXL97, PLATON and publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812005879/pk2389sup1.cif

e-68-0o857-sup1.cif^{(26.2KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812005879/pk2389Isup2.hkl

e-68-0o857-Isup2.hkl^{(114.6KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536812005879/pk2389Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1⋯O1′	0.84 (3)	2.38 (3)	2.792 (3)	111 (2)
N1—H1⋯O1′′	0.84 (3)	2.43 (3)	2.814 (3)	109 (2)
O1′—H1A⋯O1′′ⁱ	0.82	1.99	2.805 (3)	169
O1′—H1B⋯O1′ⁱⁱ	0.83	1.99	2.807 (4)	167
O1′′—H1C⋯O1′ⁱ	0.82	2.00	2.805 (3)	171
O1′′—H1D⋯O1′′ⁱⁱⁱ	0.83	2.03	2.762 (5)	148

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Acknowledgments

HSE thanks the staff of the XRD Application Laboratory, CSEM, Neuchâtel, for access to the X-ray diffraction equipment.

supplementary crystallographic information

Comment

Terpyridine and its derivatives are prototypical ligands of the pincer type family (Van Koten, 1989; Albrecht & van Koten, 2001). They have been widely used in coordination chemistry (Hofmeier & Schubert, 2004). The metal complexes obtained from pincer ligands are conformationally restricted and often thermodynamically highly stable (Hofmeier & Schubert, 2004; Li et al., 2007). The bis-benzylic alcohols of 2,6-disubstituted pyridines belonging to this class of ligands can be easily transformed (Klein et al., 2009).

The modification of these ligands by the hydrogenation of the pyridine ring installs chirality into the structure and increases the basicity and the strength of the ligand. In contrast to the 2,6-pyridinedicarboxylic acids and its derivatives, which have been extensively used, studies on the corresponding tridentate ONO-piperidine ligands containing the bis-alcohols have been very rare so far. The title compound (2) was prepared by the stereoselective cis-reduction of 2,2'-(pyridine-2,6-diyl)dipropan-2-ol (1). Herein we report on the synthesis and the crystal structure of the title compound, (2).

The molecular structure of the title molecule is illustrated in Fig. 1. The geometric parameters are very similar to those found for cis-(piperidine-2,6-diyl)dimethanol (Hartung et al., 2007). The piperidine ring has a chair conformation, with atoms N1 and C4 being displaced from the plane through atoms C2/C3/C5/C6 by 0.667 (2) and -0.662 (3) Å, respectively.

In the molecule the amine (N1) H atom is involved in two short interactions with the hydroxyl O atoms, O1' and O1'' (Table 1). The hydroxyl H atoms are each disordered over two positions, H1A/H1B and H1C/H1D. Their occupancies were initially refined before being fixed at 0.57/0.43 and 0.63/0.37, respectively. The ¹H NMR signal for the hydroxyl H atoms [δ 2.88 (bs, 2 H, OH); see archived CIF] is a broad singlet, which indicates some fluxionality of these protons in solution.

In the crystal, four symmetry related molecules are linked by O—H···O hydrogen bonds to form a cage-like arrangement, centered about the point of intersection of three 2-fold axes (Fig 2). These cages are arranged in stacks along direction [100], as shown in Fig. 3.

Experimental

The synthesis of the title compound (2) is illustated in Fig. 4. The starting material, 2,2'-(pyridine-2,6-diyl)dipropan-2-ol (1), was prepared in one step from the commercially available dimethyl pyridine-2,6-dicarboxylate, according to the method described by (Klein et al., 2009). The title compound (2), was synthesized by heating 0.5 g (2.56 mmol) of compound (1), together with 10% Pd/C (430 mg), methanol (10 ml) and acetic acid (10 ml), in an autoclave under hydrogen (50 atm), with stirring at 323 K for 12 h. For workup the reaction was filtered through a pad of celite and washed three times with dichloromethane. The solution was concentrated under vacuum to give a colourless slurry. The slurry was dissolved in dichloromethane and washed with 5% sodium hydroxide and the mixture was stirred for 5 min. The organic layer was separated and the aqueous layer was extracted three times with dichloromethane. The combined organic layers were washed with brine, dried with sodium sulfate and concentrated under vacuum to yield 0.494 g (96%) of compound (2). Melting point: 345.3 K. HRMS calcd. for [C₁₁H₂₃NO₂⁺H⁺] 224.1621; found 224.1621. Colourless rod-like crystals were obtained by slow evaporation of a solution of (2) in dichloromethane. Spectroscopic data for the title compound (2), are given the archived CIF.