Crystal structure and identification of resonance forms of diethyl 2-(3-oxoiso-1,3-dihydrobenzofuran-1-ylidene)malonate
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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]. 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 isobenzofuran unit. This delocalization is likely to be responsible for the unusual intermolecular 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 interactions are observed, which link the molecules into  chains.
Tyumentsev , M S , Foreman , M R S J , Steenari , B-M & Slawin , A M Z 2017 , ' Crystal structure and identification of resonance forms of diethyl 2-(3-oxoiso-1,3-dihydrobenzofuran-1-ylidene)malonate ' Acta Crystallographica Section E , vol 73 , no. 10 , pp. 1576-1579 . DOI: 10.1107/S2056989017013962
Acta Crystallographica Section E
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The research leading to these results received funding from the European Community's Seventh Framework Programme ([FP7/2007–2013]) under grant agreement No. 607411 (MC-ITN EREAN: European Rare Earth Magnet Recycling Network).
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