The Zwitterionic Imidazolium Salt: First Used for Synthesis of 4-Arylidene-2-phenyl-5(4H)-oxazolones under Solvent-Free Conditions

Table 1

Evaluation of several sulfonates in the Erlenmeyer reaction.

Entry	Catalyst	Reaction temperature (°C)	Reaction time; (h)	Isolated yields; (%)^a
1	Imidazolium salt (1)	60	4	76
2	CH3SO3H	60	4	16
3	NH2SO3H	60	4	7

aBased on benzaldehyde; isolated yields based on benzaldehyde; 5 mmol benzaldehyde, 5.5 mmol hippuric acid, 10 mmol% catalyst, and 15 mmol acetic anhydride were used.