Diallyl 5-[(4-hexyl­oxyphen­yl)imino­meth­yl]-m-phenyl­ene dicarbonate

Ana María Herrera-González; Delia López-Velázquez; Sylvain Bernès

doi:10.1107/S1600536809041142

. 2009 Oct 23;65(Pt 11):o2810–o2811. doi: 10.1107/S1600536809041142

Diallyl 5-[(4-hexyloxyphenyl)iminomethyl]-m-phenylene dicarbonate

Ana María Herrera-González ^a, Delia López-Velázquez ^b, Sylvain Bernès ^c,^*

PMCID: PMC2971017 PMID: 21578402

Abstract

The title molecule, C₂₇H₃₁NO₇, an imine derivative bearing both carbonate and allyl functionalities, was synthesized in the hope of obtaining a mesogenic polymerizable material. The allylcarbonate arms are fully disordered over two sets of sites, reflecting a large degree of rotational freedom about σ bonds [occupancies: 0.665 (9)/0.335 (9) for one substituent, 0.564 (9)/0.436 (9) for the other]. In contrast, the hexyl chain is ordered, and presents the common all-trans extended conformation. The benzene rings connected via the imine group make a dihedral angle of 9.64 (11)°. In the crystal, the Y-shaped molecules are weakly associated into centrosymmetric dimers through pairs of C—H⋯O(hexyl) contacts. The resulting layers of dimers, approximately parallel to (2 Inline graphic 5), are closely packed in the crystal, allowing π⋯π interactions between benzene rings of neighboring layers: the separation between the centroid of the benzene ring substituted by allylcarbonate and the centroid of the benzene ring bearing the hexyloxy group in the adjacent layer is 3.895 (1) Å.

Related literature

For the crystal structure of 4-(hexyloxy)aniline, used as a starting material, see: Herrera et al. (2005 ▶). For the crystal structures of molecules with allycarbonate functionality, see: Michelet et al. (2003 ▶); Burns & Forsyth (2008 ▶); Flores Ahuactzin et al. (2009 ▶). For applications of the above molecules as polymerizable monomers, see: Herrera (2006 ▶).

Experimental

Crystal data

C₂₇H₃₁NO₇
M _r = 481.53
Triclinic,
a = 8.6407 (11) Å
b = 10.9711 (14) Å
c = 15.014 (2) Å
α = 102.756 (11)°
β = 103.368 (12)°
γ = 101.092 (12)°
V = 1305.4 (3) Å³
Z = 2
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 298 K
0.6 × 0.6 × 0.2 mm

Data collection

Bruker P4 diffractometer
Absorption correction: none
8105 measured reflections
5927 independent reflections
3505 reflections with I > 2σ(I)
R _int = 0.027
3 standard reflections every 97 reflections intensity decay: 1%

Refinement

R[F ² > 2σ(F ²)] = 0.053
wR(F ²) = 0.165
S = 1.04
5927 reflections
409 parameters
20 restraints
H-atom parameters constrained
Δρ_max = 0.14 e Å⁻³
Δρ_min = −0.15 e Å⁻³

Data collection: XSCANS (Siemens, 1996 ▶); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809041142/ci2922sup1.cif

e-65-o2810-sup1.cif^{(28.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809041142/ci2922Isup2.hkl

e-65-o2810-Isup2.hkl^{(290.1KB, 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
C13—H13A⋯O15ⁱ	0.93	2.60	3.511 (2)	166

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Symmetry code: (i) Inline graphic .

Acknowledgments

AMH is indebted to PROMEP (Mexico) for providing a research grant. Partial support from VIEP-BUAP (project Nos. 7/I/NAT/05 and 36/NA/06–1) is gratefully acknowledged.

supplementary crystallographic information

Comment

We are involved in a general project dealing with the synthesis of new allyl carbonate compounds, with the hope to obtain suitable monomers for the preparation of glasses with designed properties (Herrera, 2006). The previous report in this series was about allyl 4-hydroxyphenyl carbonate (Flores Ahuactzin et al., 2009), which was found to display a disordered allyl functionality in the solid-state.

The title molecule, (I), is based on a benzene core di-substituted by allyl carbonate groups. The molecule is completed by a third substituent, derived from 4-(hexyloxy)aniline, for which the X-ray structure has been also reported (Herrera et al., 2005). The whole molecule is a Schiff base including chemical features expected to give a mesogenic behavior to the material. This compound can be prepared following two routes, starting from 3,5-dihydroxybenzaldehyde. The two steps route (Fig. 1 and experimental) consists of the functionalization of 3,5-dihydroxybenzaldehyde using allylchloroformate, followed by condensation with 4-(hexyloxy)aniline, to form the Schiff base. The alternative route (Herrera, 2006) is to prepare the Schiff base prior to functionalize with allylchloroformate.

The resulting compound (Fig. 2) is characterized by strongly disordered allylcarbonate substituents: five of the seven atoms in each substituent are disordered over two sites (Fig. 2, inset), with occupancies being 0.564 (9) and 0.436 (9) for one arm, and 0.665 (9) and 0.335 (9) in the other. A remarkable arrangement is observed in the first substituent (O22···C28), where disordered final CCH₂ groups are placed almost perpendicular, reflecting a high degree of free rotation about σ bonds in these substituents. This behavior, resulting in a variety of stable conformations for the allylcarbonate functional groups, has been also observed in related structures (Michelet et al., 2003; Burns & Forsyth, 2008; Flores Ahuactzin et al., 2009). In (I), the observed disorder may be related to the rather low melting point of this material, 318 K (45° C).

The imine component is ordered, and the hexyl chain presents the common all-trans conformation. The complete molecule is Y-shaped, with a small dihedral angle of 9.64 (11)° between the benzene rings.

The crystal structure (Fig. 3) contains centrosymmetric dimers, formed through weak C—H···O(hexyl) contacts. Dimers are arranged in planes, approximately parallel to the (225) in the crystal. Two neighboring layers are in close contact viaπ···π interactions between benzene rings (Fig. 3, inset). The centroid of the benzene ring substituted by allylcarbonate and the centroid of the benzene ring bearing the hexyloxy group in the following layer (symmetry code: x - 1, y, z), are separated by 3.895 (1) Å.

Experimental

A solution of 3,5-dihydroxybenzaldehyde (0.5 g, 3.6 mmol) in CH₂Cl₂ and pyridine as catalyst was cooled in an ice bath, and allylchloroformate (0.95 g, 7.8 mmol) was added dropwise under stirring at 278 K. The mixture was stirred for 4 h under an atmosphere of Ar. The reaction was then treated with a solution of HCl at 5%, and concentrated under reduced pressure, yielding the crude aldehyde (3) as a liquid (Fig. 1). This intermediate was purified by column chromatography on silica, eluting with CH₂Cl₂. Yield 91%. To a solution of (3) (0.5 g, 1.6 mmol) in dry ethanol (30 ml) was added 4-(hexyloxy)aniline (0.33 g, 1.6 mmol) under an atmosphere of Ar. The reaction mixture was then heated to 325 K for 18 h. The reaction mixture was cooled to room temperature and solvent eliminated under reduced pressure, affording (I), which was purified by column chromatography on silica, eluting with CH₂Cl₂ and then recrystallized from methanol (93% yield; brown crystals).