Synthesis of 4-arylidene-2-aryl-5(4h)-oxazolones using the Boc₂O/pyridine system

The possibility of using the tert-butyl dicarbonate/pyridine (Boc₂O/Py) system for the synthesis of 4-arylidene-2-phenyl-5(4H)-oxazolones was studied. The ratio of Boc₂O/pyridine varied concerning hippuric acid, as well as the reaction conditions. It has been found that the best results are obtained when all the reagents, except for the aldehyde, are stirred at room temperature and the reaction mixture is refluxed for 1 h after the addition of the aldehyde. Boc-O-protected oxazolones have been used to synthesize derivatives of the green fluorescent protein chromophore