Table 3. Optimization of the Carbonylative Sonogashira Coupling Reactions of 4-Iodoanisole (1a) and Phenylacetylene (2a)^a.

entry	NHC-Pd-Py (mol %)	solvent	T (°C)	base	time (h)	yield 3aa (%)b
1	Pd-C3	toluene	80	Et3N	1	10
	(0.01)
2	Pd-C3	toluene	100	Et3N	1	20
	(0.01)
3	Pd-C3	toluene	120	Et3N	1	52
	(0.01)
4	Pd-C3	toluene	100	Et3N	3	55
	(0.01)
5	Pd-C3	toluene	120	Et3N	3	91
	(0.01)
6	Pd-C3	toluene	120	Et3N	3	99
	(0.05)
7	Pd-C3	toluene	120	Et3N	3	99
	(0.03)
8	Pd-C3	toluene	100	Et3N	3	97
	(0.03)
9	Pd-C3	toluene	100		3	0
	(0.03)
10	Pd-C3	toluene	100	KOH	3	8
	(0.03)
11	Pd-C3	toluene	100	K2CO3	3	5
	(0.03)
12	Pd-C3	THF	100	Et3N	3	61
	(0.03)
13	Pd-C3	DMF	100	Et3N	3	73
	(0.03)
14	Pd-C3	CH3CN	100	Et3N	3	84
	(0.03)
15	Pd-C2	toluene	100	Et3N	3	79
	(0.03)
16	Pd-C1	toluene	100	Et3N	3	85
	(0.03)
17	Pd(PPh3)2Cl2	toluene	100	Et3N	3	48
	(0.03)
18	Pd(PhCN)2Cl2	toluene	100	Et3N	3	31
	(0.03)
19	PdBr2	toluene	100	Et3N	3	22
	(0.03)

^aReaction conditions: 4-iodoanisole (1.0 mmol), phenylacetylene (1.5 mmol), base (2.0 mmol), solvent (5 mL), CO (200 psi).

^bIsolated yield.