Greener approach: Ionic liquid [Et<sub>3</sub>NH][HSO<sub>4</sub>]-catalyzed multicomponent synthesis of 4-arylidene-2-phenyl-5(4<i>H</i>)oxazolones under solvent-free condition

<p>We have developed simple, greener, safer multicomponent synthesis series of 4-arylidene-2-phenyl-5(4<i>H</i>) oxazolones <b>4(a-r)</b> catalyzed by Bronsted acid ionic liquid as triethylammonium hydrogen sulfate [Et<sub>3</sub>NH][HSO<sub>4</sub>] and catalytic amount of acetic anhydride and sodium acetate with excellent yields (90–99%). The protocol offers economical, environmentally benign, solvent-free conditions, and recycle–reuse of the catalyst and easily available starting as benzoyl chloride <b>1</b>, amino acid <b>2</b> and a variety of aldehydes <b>3</b>. The cyclization followed by condensation of benzoyl chloride, amino acid, and a variety of aldehydes catalyzed by ILs [Et<sub>3</sub>NH][HSO<sub>4</sub>] and catalytic amount of acetic anhydride and sodium acetate. The final products were confirmed by their characterization data such as FTIR, <sup>1</sup>H-NMR, <sup>13</sup>C-NMR, Mass, high-resolution mass spectra and were compared with its reported method.</p>