4,4-Bis(1H-pyrrol-2-yl)penta­nol

Guillaume Journot; Reinhard Neier; Helen Stoeckli-Evans

doi:10.1107/S1600536809054269

. 2010 Jan 16;66(Pt 2):o393. doi: 10.1107/S1600536809054269

4,4-Bis(1H-pyrrol-2-yl)pentanol

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

PMCID: PMC2979789 PMID: 21579814

Abstract

The title achiral compound, C₁₃H₁₈N₂O, crystallized in the chiral monoclinic space group P2₁. The pyrrole rings are inclined to one another by 62.30 (11)°, and the propanol chain is in an extended conformation. In the crystal, the two pyrrole NH groups are involved in intermolecular N—H⋯O hydrogen bonds, leading to the formation of a helical arrangement propagating along the b axis. An interesting feature of the crystal structure is the absence of any conventional hydrogen bonds involving the hydroxy H atom. There is, however, a weak intermolecular O—H⋯π interaction involving one of the pyrrole rings.

Related literature

For substituted calix[4]pyrroles, see: Gale et al. (1998 ▶); Sessler & Davis (2001 ▶); Sessler et al. (2003 ▶). For the crystal structures of similar compounds, see: Warriner et al. (2003 ▶); Maeda et al. (2007 ▶); Sobral et al. (2003 ▶). For details of hydrogen-bonding graph-set analysis, see: Bernstein et al. (1995 ▶). For a description of the Cambridge Structural Database, see: Allen (2002 ▶).

Experimental

Crystal data

C₁₃H₁₈N₂O
M _r = 218.29
Monoclinic,
a = 8.4721 (15) Å
b = 8.2111 (9) Å
c = 8.7120 (15) Å
β = 101.530 (14)°
V = 593.82 (16) Å³
Z = 2
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 173 K
0.45 × 0.45 × 0.40 mm

Data collection

Stoe IPDS-2 diffractometer
6119 measured reflections
1701 independent reflections
1518 reflections with I > 2σ(I)
R _int = 0.032

Refinement

R[F ² > 2σ(F ²)] = 0.030
wR(F ²) = 0.077
S = 0.97
1701 reflections
159 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.19 e Å⁻³
Δρ_min = −0.16 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: ORTEP-3 (Farrugia, 1997 ▶) and Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809054269/is2505sup1.cif

e-66-0o393-sup1.cif^{(17.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809054269/is2505Isup2.hkl

e-66-0o393-Isup2.hkl^{(83.8KB, hkl)}

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—H1N⋯O1ⁱ	0.88 (2)	2.05 (2)	2.9238 (18)	174.3 (19)
N2—H2N⋯O1ⁱⁱ	0.90 (2)	2.06 (2)	2.9529 (18)	171.5 (19)
O1—H1O⋯Cg1ⁱⁱⁱ	0.87 (3)	2.53	3.20	135
O1—H1O⋯Cg2ⁱⁱⁱ	0.87 (3)	2.64	3.10	114

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) . Cg1 and Cg2 are the centroids of the C7=C8 bond and the N2/C5–C8 pyrrole ring, respectively.

Acknowledgments

HSE is grateful to the XRD Application LAB, Microsystems Technology Division, Swiss Center for Electronics and Microtechnology, Neuchâtel, for access to the X-ray diffraction equipment.

supplementary crystallographic information

Comment

The title compound (systematic name: 4,4-di(1H-pyrrol-2-yl)pentan-1-ol) was prepared as a building block for the formation of substituted calix[4]pyrroles. The latter have been shown to form extremely interesting host–guest complexes with various anions (Gale et al., 1998; Sessler and Davis, 2001; Sessler et al., 2003).

The structure of the title compound is shown in Fig. 1, and the geometrical parameters are given in the Supplementary Information and the archived CIF. This achiral compound crystallized in the chiral monoclinic space group P2₁. The bond lengths and angles are similar to those observed in 5 similar 1,1-bis(2-pyrrolyl)ethane compounds in the Cambridge Crystal Structure Database (CSD, V5.30, last update Sep. 2009; Allen et al., 2002). These include the (3,4,5-tribromo-2-pyrrolyl) derivative (Warriner et al., 2003; AJARIM), the o-, m- and p-pyridyl derivaties (Maeda et al., 2007; CIGKIN, CIGKEJ, CIGKAF, respectively) and the phenyl derivative (Sobral et al., 2003; JADHUS), all of which crystallized as racemates.

In the title compound the pyrrole ring mean-planes are inclined to one another by 62.30 (11)°, and the propanol chain is in the extended conformation. In the 5 compounds located in the CSD this angle varies between 68.5 to 89.6 °.

In the crystal the molecules are linked by conventional N—H···N intermolecular hydrogen bonds leading to the formation of helical chains propagating along the b axis (Fig. 2 and Table 1). The basic unitary hydrogen bonding graph set can be described by an R²₃(16) ring, while the basic binary graph set is a C(8) chain. This gives an extended notation of C(8)[R²₃(16)] (Bernstein et al., 1995). A fuller hydrogen bonding graph set analysis can be obtained using the program Mercury (Macrea et al., 2006).

An O—H···π interaction is also observed in the crystal structure (Fig. 2 and Table 1). It can be considered either to involve the C7═C8 bond (centroid = Cg1) with an O—H···π angle of ca 135°, or a weaker interaction involving the pyrrole ring (N2/C5—C8; centroid = Cg2), with an O—H···π angle of only ca 114° [these data were obtained using the program Mercury (Macrae et al., 2006)].

Experimental

A mixture of 3-acetylpropanol (10 ml, 98.6 mmol) and pyrrole (50 ml, 0.720 mol) were stirred for 5 min and then trifluoro acetic acid [TFA] (0.74 ml, 9.6 mmol, 0.097 equiv.) was added. The whole mixture was stirred foran additional 5 min and then quenched with aqueous NaOH (0.1 N, 30 ml). The mixture was extracted with CH₂Cl₂ (50 ml × 2) and the organic layer dried (Na₂SO₄). The solvent was removed in vacuo and the remaining oil crystallized with dichloromethane (20 ml). The colourless block-like crystals obtained were washed with 2-propanol [m.p. 372 K; Yield 14.1 g (65.3%)]. ¹H NMR (CDCl₃) δ 7.85 (bs, 2H, N—H), 6.63–6.61 (ddd, J = 2.7 Hz,2.7 Hz, 1.6 Hz, 2H, pyrrolic-H_1–8), 6.15–6.13 (ddd, J = 3.3 Hz, 2.7 Hz, 1.6 Hz, 2H, pyrrolic-H_2–7), 6.10–6.08 (ddd, J = 3.3 Hz, 1.6 Hz,1.6 Hz, 2H, pyrrolic-H_3–6), 3.61–3.57 (td, J = 6 Hz, 5 Hz, 2H, –O—CH2₁₂), 2.07–2.03 (m, 2H, –CH2₁₀–), 1.59 (s, 3H, –CH3₁₃), 1.51–1.43 (m, 2H,-CH2₁₁–), 1.24–1.20 (t, J = 5 Hz, 1H, –OH); ¹³C NMR (CDCl₃)δ 137.97 (C_4–5), 117.15 (C_1–5), 107.92 (C_2–7),104.77 (C_3–6), 63.26 (C₁₂), 39.04 (C₉), 37.35 (C₁₀),28.01 (C₁₁), 26.62 (C₁₃). MS calcd. for C₁₃H₁₈N₂O 218.14, found 217.13 (M—H⁺).