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Paper | Regular issue | Vol 57, No. 8, 2002, pp.1445-1459
Published online, 1st January, 1970
DOI: 10.3987/COM-02-9504
Reactions of α-Oxo Ketenes with Amides: Experimental Data and Semiempirical AM1 Molecular Orbital Calculations

Emin Saripinar,* Ilhan Ozer Ilhan, and Yunus Akçamur

*Department of Chemistry, Arts and Sciences Faculty, Erciyes University, TR-38039 Kayseri, Turkey

Abstract

The thermal decomposition of 4-acyl substituted furan-2,3-diones (1a, b) leads to the α-oxo ketenes (2a, b) as an intermediate which undergoes nucleophilic addition reactions with amides. Some of α-N-acyl-oxo-amide derivatives (4a-h) obtained show keto-enol tautomerism. The reaction mechanism of ketene (R1) with formamide (R2) are calculated by AM1 method. Transition states (TS1 and TS2) were further confirmed by vibrational analysis and characterized by the corresponding imaginary vibration modes and frequencies. According to calculations, intermediate (IN) is in the planar zwitterion structure. The transition structure (TS2) has almost a planar structure. Analysis of the molecular orbitals indicates that the reaction is best described as pseudopericyclic.