The influence of solvents and temperature on preparation of 6a^a.

Entry	Solvent	Temperature (°C)	Yield (%)
1	H2O	25	68
2	H2O	60	99
3	H2O	70	99
4	Non	80	82
5	EtOH	40	95
6	DCM	60	21
7	MeCN	60	26
8	THF	60	33
9	Dioxane	60	15
10	Toluene	60	Trace

^aThe mixture of 4a (1 mmol), 5a (1 mmol), NH₄OAc (2.5 mmol) and 3a (5 mol%) in solvent (5 mL) was sonicated for 5 min at different temperatures.