The results of optimization of reaction conditions on the model reaction^a.

Entry	Amount of MC–SO3H (mg)	Temperature (°C)	Time (min)	Yieldb (%)
1	20	R.T	120	Trace
2	20	50	120	62
3	20	80	120	96
4	5	80	120	37
5	10	80	120	79
6	12	80	120	96
7	15	80	120	96
8	12	80	60	96
9	12	80	30	96
10	12	80	20	90
11	12	80	10	69

^aReaction conditions: 4-bromobenzaldehyde (1 mmol), benzil (1 mmol), ammonium acetate (3 mmol), EtOH (4 mL).

^bIsolated yield.