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

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 (25), 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.

The title molecule, C 27 H 31 NO 7 , 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 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-HÁ Á ÁO(hexyl) contacts. The resulting layers of dimers, approximately parallel to (225), are closely packed in the crystal, allowing Á Á Á 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 .
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. 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 CCH 2 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 via π···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.

S2. Experimental
A solution of 3,5-dihydroxybenzaldehyde (0.5 g, 3.6 mmol) in CH 2 Cl 2 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 supporting information on silica, eluting with CH 2 Cl 2 . 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 CH 2 Cl 2 and then recrystallized from methanol (93% yield; brown crystals).

Figure 1
The synthetic route used for the preparation of (I).  The molecular structure of (I), with displacement ellipsoids shown at the 30% probability level. Only major disorder components are shown. The inset represents the central benzene ring with disordered allylcarbonate groups: the major disorder component is shown in red and the minor component in blue; site occupation factors are quoted.