(E)-2,2-Dimethyl-5-(3-phenylallylidene)-1,3-dioxane-4,6-dione

The title compound, C15H14O4, was prepared by the reaction of 2,2-dimethyl-1,3-dioxane-4,6-dione and (Z)-3-phenylacrylaldehyde in ethanol. The dioxane ring is in a sofa conformation with the C atom bonded to the two methyl groups forming the flap. With the exception of the flap atom and the methyl group C atoms, all other non-H atoms are essentially planar, with an r.m.s. deviation of 0.067 (1) Å. The crystal structure is stabilized by weak intermolecular C—H⋯O hydrogen bonds.

The title compound, C 15 H 14 O 4 , was prepared by the reaction of 2,2-dimethyl-1,3-dioxane-4,6-dione and (Z)-3-phenylacrylaldehyde in ethanol. The dioxane ring is in a sofa conformation with the C atom bonded to the two methyl groups forming the flap. With the exception of the flap atom and the methyl group C atoms, all other non-H atoms are essentially planar, with an r.m.s. deviation of 0.067 (1) Å . The crystal structure is stabilized by weak intermolecular C-HÁ Á ÁO hydrogen bonds.

D-HÁ
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: LH5147).

Comment
Starting with its discovery and correct structural assignment, Meldrum's acid has become a widely used reagent in organic synthesis (Kuhn et al., 2003;Casadesus et al., 2006) owing to the interesting conformational features of the products.
We have recently reported the crystal structure of 5-(2-fluorobenzylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione (Zeng et al. 2009). As part of our search for new Meldrum's acid, the title compound (I) has been synthesized and its structure is reported herein. The molecular structure of (I) is shown in Fig. 1. The dioxane ring is in a sofa conformation with the C atom bonded to the two methyl groups forming the flap. With the exception of the flap atom and the methyl group C atoms, all other non-hydrogen atoms are essentially planar with an rms deviation of 0.067 (1)Å. The deviation of atom C13 from the mean-plane formed by O1/O2/C11/C12/C10 is 0.270 (1)Å. The crystal structure is stabilized by weak intermolecular C-H···O hydrogen bonds (Table 1).

Experimental
The mixture of malonic acid (6.24 g, 0.06 mol) and acetic anhydride(9 ml) in strong sulfuric acid (0.25 ml) was stirred with water at 303K, After dissolving, propan-2-one (3.48 g, 0.06 mol) was added dropwise into solution for 1 h. The reaction was allowed to proceed for 2 h. The mixture was cooled and filtered, and then an ethanol solution of (Z)-3-phenylacrylaldehyde (7.92g,0.06 mol) was added. The solution was then filtered and concentrated. Single crystals were obtained by evaporation of an petroleum ether-ethylacetate (4:1 v/v) solution of (I) at room temperature over a period of several days.

Refinement
The H atoms were placed in calculated positions (C-H = 0.93 and 0.96 Å), and refined as riding with U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C). Fig. 1. The molecular structure of (I), drawn with 30% probability ellipsoids and spheres of arbritrary size for the H atoms.