Reaction of 3-formylchromone-<i>N</i>-benzoylhydrazone with ketenes. Synthesis and structural studies of chromone 1,3,4-oxadiazolines
作者:George C. Kaspentakis、Constantinos A. Tsoleridis、Julia Stephanidou-Stephanatou
DOI:10.1002/jhet.5570440223
日期:2007.3
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
Mechanochemical synthesis of 2,5-disubstituted1,3,4-oxadiazoles was developed as an environmentally benign alternative to conventional solvent-based methods. In the presence of triphenylphosphine and trichloroisocyanuric acid, N-acylbenzotriazoles condense with acylhydrazides leading to oxadiazoles derivatives in good to excellent yields within minutes. The approach circumvents the need for strictly