5-Cyano-1,3-phenylene diacetate

In the title molecule, C11H9NO4, the two acetoxy groups are twisted from the plane of the benzene ring by 67.89 (4) and 53.30 (5)°. Both carbonyl groups are on the same side of the aromatic ring. In the crystal, weak C—H⋯O hydrogen bonds link molecules into layers parallel to the ac plane. The crystal packing exhibits π–π interactions between the aromatic rings, indicated by a short intercentroid distance of 3.767 (3) Å.

In the title molecule, C 11 H 9 NO 4 , the two acetoxy groups are twisted from the plane of the benzene ring by 67.89 (4) and 53.30 (5) . Both carbonyl groups are on the same side of the aromatic ring. In the crystal, weak C-HÁ Á ÁO hydrogen bonds link molecules into layers parallel to the ac plane. The crystal packing exhibitsinteractions between the aromatic rings, indicated by a short intercentroid distance of 3.767 (3) Å .

Comment
In the synthesis of a class of organogelators, it was necessary to shorten the synthesis of 3,5-dialkoxybenzyl amine derivatives by utilizing 5-cyano-1,3-phenylene diacetate as an intermediate. Typical synthesis of these benzyl amine derivatives started at the alkylation of methyl 3,5-dihydroxybenzoate, followed by several synthetic steps that required lithium aluminium hydride (LAH), and sodium azide (Carr, 2008). By forming the nitrile and catalytically reducing it, the hazardous chemicals (LAH, NaN 3 ) are removed from the synthetic scheme creating a greener process. The 3-acetoxy-5carbamoylphenyl acetate is dehydrated using cyaniuric acid chloride in dimethylformamide (Bhattacharyya et al., 2012).
The crude solid nitrile is isolated by diluting the reaction mixture with bicarbonate solution and vacuum filtration.
Investigated compound ( Fig. 1) crystallized in the monoclinic crystal system and the molecule occupies a general position in the unit cell. Both acetoxy groups are planar and form dihedral angles with the mean plane of the Ph-ring equal to 67.89 (4) and 53.30 (5) °, respectively and have similar geometry found in the structure of benzene-1,3,5-triyl triacetate (Haines & Hughes, 2009). In the crystal, the molecules (I) form centrosymmetric dimers through partial π-π stacking interactions between aromatic rings. Such mutual orientation of the molecules is a reason of the existance of weak intermolecular C···C contacts with distances from 3.532 Å (C1···C2) to 3.464 Å (C1···C3) that are slightly bigger than their sum of the van der Waals radii. At the same time, two weak intermolecular C-H···O hydrogen bonds with H···O distances of 2.54 and 2.48 Å (Table 1), respectively, link molecules into layers parallel to ac plane. The crystal packing exhibits π-π interactions between the aromatic rings proved by short intercentroid distance of 3.767 (3) Å.

Experimental
In a 250 ml round bottom flask equipped with a stir bar, 8.50 g (35.7 mmol) 3,5-diacetoxybenzamide was suspended in 25 ml of dry N,N-dimethylformamide (DMF). The reaction was placed under nitrogen. A solution of 4.40 g (23.8 mmol) 2,4,6-trichloro[1,3,5]triazine (TCT) in 15 ml of dry DMF was generated. After the TCT solution turned yellow (10 min.), it was added drop wise to the amide suspension over a period of 15 min. After 30 min. all amide dissolved. The reaction was stirred at room temperature overnight. At which time, 150 ml of 0.5 M sodiumbicarbonate solution was added slowly with vigorous stirring. A white solid was collected by vacuum filtration. The solid was washed with a copious amount of water and left to air dry, producing 7.9 g (97% yield) of 3-acetoxy-5-cyanophenyl acetate. m.p. 350 K (Ellis et al., 1976 168.4, 151.4, 122.8, 120.8, 117.2, 113.8, 21.1 The nitrile was then recrystallized from the slow evaporation of acetone with 10% water, giving X-ray quality crystals. Their positions were constrained so that the U iso (H) was equal to 1.2Ueq and 1.5 U eq of their respective parent atoms.

Figure 1
Moleculear structure of the title compound showing the atomic numbering and 50% probability displacement ellipsoids. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.