Table 1. Optimization of the reaction conditions for the Ullmann coupling of 4-iodoanisole (1a) and methylamine (2a)^a).

Entry	Catalyst	Base	Temperature (°C)	Time (h)	Yield (%)b)	TON
1	Cu-A	Cs2CO3	110	24	64	46.3
2	Cu-B	Cs2CO3	110	3	76	56.2
3c)	Cu-B	Cs2CO3	110	3	80	59.2
4	Cu-B	K2CO3	110	24	53	39.2
5	Cu-B	K3PO4	110	24	NR	0
6	Cu-B	NEt3	110	24	NR	0
7d)	Cu-B	Cs2CO3	110	24	NR	0
8e)	Cu-B	Cs2CO3	110	24	NR	0
9f)	Cu-B	Cs2CO3	25	24	NR	0
10	Cu0 NPs	Cs2CO3	110	24	50	36.2
11	Cu0-Carbon Black	Cs2CO3	110	24	50g)	35.9
12	DVAC-1	Cs2CO3	110	24	NR	0

^a)Reaction conditions: 4-iodoanisole (1a, 1 mmol, 234 mg), methylamine (2a, 40 wt % aqueous solution, 2.5 mL, 28.9 mmol) and inorganic base (2 mmol);

^b)Isolated yields;

^c)The reaction was conducted using 1a (10 mmol), 2a (40 wt % aqueous solution, 25 mL), and Cs₂CO₃ (20 mmol);

^d)Methyl amine (40 wt% aqueous solution, 1 mL) and N,N-dimethylformamide (2 mL);

^e)Methyl amine (40 wt% aqueous solution, 1 mL) and dimethyl sulfoxide (2 mL);

^f)The reaction was performed at room temperature;

^g)Determined by¹H NMR spectra. NR = no reaction; TON = turn over number (mole of substrate converted per mole of active site).