Table 1.

Investigation of Palladium Precatalysts and Reoxidants

Entry	Pd source	Reoxidant /equiv	Solvent	Gas atm	Time (h)	Yield (%)a
1	Pd(OAc)2	Cu(OAc)2 / 1	toluene	O2	12	92
2	Pd(OAc)2		toluene	O2	12	5
3		Cu(OAc)2 / 1	toluene	O2	12	0
4	Pd(O2CCF3)2	Cu(OAc)2 / 1	toluene	O2	24	70
5	PdCl2	Cu(OAc)2 / 1	toluene	O2	24	21
6	PdCl2(CH3CN)2	Cu(OAc)2 / 1	toluene	O2	24	27
7	PdCl2(PPh3)2	Cu(OAc)2 / 1	toluene	O2	24	67b
8	Pd(OAc)2	PPh3 / 0.2	toluene	O2	12	5
9	Pd(OAc)2	pyridine / 0.2	toluene	O2	12	1
10	Pd(OAc)2	PhI(OAc)2 / 0.2	DCEc	air	12	25
11	Pd(OAc)2	K2S2O8 / 5	DCEd	air	12	2
12	Pd(OAc)2	benzoquinone / 1	toluene	air	12	4

^aGC yield was determined with respect to a calibrated internal standard.

^bAbout 5–10% diacetylated amide of 2-aminobiphenyl was observed.

^cSlightly higher yield was obtained in dichloroethane than in methylene chloride.

^dThe reaction was performed at 80 °C in dichloroethane; the same low yield was observed with or without bases.