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

Table 2

Reaction conditions in the Erlenmeyer reaction.

Entry	The amount of catalysts; (mmol %)	Reaction temperature; (°C)	Reaction time; (h)	Isolated yields; (%)^a
1	0	60	4	41^b
2	2.5	60	4	67
3	5	60	4	75
4	10	60	4	76
5	20	60	4	78
6	5	25	24	15
7	5	40	4	56
8	5	60	4	75
9	5	Reflux temperature	4	62
10	5	60	1.5	53
11	5	60	2.5	56
12	5	60	4	75
13	5	60	5	75

aBased on benzaldehyde; isolated yields based on benzaldehyde; 5 mmol benzaldehyde, 5.5 mmol hippuric acid and 15 mmol acetic anhydride were used.
^bNot isolated yield, some by-products were found.