Reaction of 3-formylchromone-N-benzoylhydrazone with ketenes. Synthesis and structural studies of chromone 1,3,4-oxadiazolines

Article abstract of DOI:10.1002/jhet.5570440223

(Chemical Equation Presented) The reaction of 3-formylchromone-N- benzoylhydrazone with ketenes, prepared in situ from the corresponding acid chlorides 2a-d and the mixed anhydride 2e was studied. In all cases 2-(4′-oxo-4′H-3′-chromyl)-5-phenyl-2,3-dihydro-1,3, 4-oxadiazoles (3) were isolated in yields varying from 40 to 80%. A full structure assignment of all products has been made on the basis of 1D and 2-D (COSY H-H, COSY C-H, COLOC C-H) NMR spectra. A plausible reaction mechanism is also proposed based on theoretical approaches and experimental results.