Table 1. Optimization of the Reaction Conditions^a.

entry	[Cu] (X equiv)	ESF (Y equiv)	time (h)	yield (2a, %)b
1c	CuO (2.0)	2.0	20	20
2d	CuO (2.0)	2.0	20	74
3	CuO (2.0)	2.0	20	89
4	CuO (1.0)	2.0	20	91
5	/	2.0	20	trace
6	CuO (1.0)	4.0	20	73
7	CuO (1.0)	1.5	20	70
8e	CuO (1.0)	1.5	20	80
9f	CuO (1.0)	2.0	20	87
10	CuO (1.0)	2.0	5	N.D.
11	CuO (1.0)	2.0	48	89

^aReaction conditions: a mixture of benzoic acid (1a, 0.1 mmol), [Cu], ESF, and anhydrous MeCN (2 mL) reacted at 80 °C under argon atmosphere for the corresponding time.

^bThe yields were determined by HPLC using 2a as the external standard (t_R = 7.5 min, λ_max = 229.9 nm, water/acetonitrile = 50:50 (v/v)).

^cIn the air.

^dUndried MeCN (2 mL).

^eReacted at 70 °C.

^fReacted at 90 °C.