Abstract
The reaction of diethyl malonate with phthaloyl chloride in aceto-nitrile in the presence of tri-ethyl-amine and magnesium chloride results in the formation of the title compound, diethyl 2-(3-oxo-1,3-di-hydro-2-benzo-furan-1-yl-idene)propane-dioate, C15H14O6. One of the ester groups of the diethyl malonate fragment is almost coplanar with the isobenzo-furan unit, while the plane of the other group is perpendicular to it [dihedral angles = 5.45 (3) and 83.30 (3)°, respectively]. The C-C and C-O distances both in the heterocyclic furan ring and the diethyl malonate fragment are indicative of the dipolar delocalization occurring within the isobenzo-furan unit. This delocalization is likely to be responsible for the unusual inter-molecular O⋯O contact [2.756 (2) Å], established between the O atom of the furan ring and the carbonyl O atom of the diethyl malonate fragment. In the crystal, weak C-H⋯O inter-actions are observed, which link the mol-ecules into [100] chains.
Highlights
The reaction of diethyl malonate with phthaloyl chloride in acetonitrile in the presence of triethylamine and magnesium chloride results in the formation of the title compound, diethyl 2-(3-oxo-1,3-dihydro-2-benzofuran-1-ylidene)propanedioate, C15H14O6
One of the ester groups of the diethyl malonate fragment is almost coplanar with the isobenzofuran unit, while the plane of the other group is perpendicular to it [dihedral angles = 5.45 (3) and 83.30 (3), respectively]
According to the structure of the resonance form (Ia) a partial positive charge is localized on the oxygen atom of the heterocyclic furan ring, and one of the carbonyl oxygen atoms of the diethyl malonate fragment carries a partial negative charge, which should lead to an electrostatic attraction of these two oxygen atoms
Summary
The structural analysis of diethyl 2-(3-oxoisobenzofuran1(3H)-ylidene)malonate (I) was undertaken as part of a study into the synthesis of new reagents for the recovery of trivalent lanthanide metal ions by liquid–liquid extraction. In turn (IV) was to be made by the reaction of diethyl malonate with phthaloyl chloride. It is already known that acid chlorides react with diethyl malonate when treated with a combination of triethylamine and a mild Lewis acid (magnesium chloride) in acetonitrile (Rathke & Cowan, 1985). Instead of (IV), an organic product, which contained two ethyl groups in different electronic environments, was obtained in this reaction. Crystals of this compound were grown and examined with singlecrystal X-ray diffractometry, and the product was found to be the title compound, (I). The formation of (I) can be rationalized by the nucleophilic attack of the oxygen atom (in an enol form) of the keto-diethylmalonate group on the carbon atom of the unreacted acid chloride group.
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