Optimization studies for palladium-catalysed C–H arylation of benzophosphole 2a with 4-iodotoluene 3a^a.

Entry	Ligand	Base (equiv.)	Conditions	Yield of 4aab (%)
1		NaOtBu (2.0)	90 °C, 16 h	66
2	SPhos	NaOtBu (2.0)	90 °C, 16 h	21
3	XPhos	NaOtBu (2.0)	90 °C, 16 h	19
4	PPh2Cy	NaOtBu (2.0)	90 °C, 16 h	56
5	PPh3	NaOtBu (2.0)	90 °C, 16 h	39
6		KOtBu (2.0)	90 °C, 16 h	68
7		LiOtBu (2.0)	110 °C, 16 h	21
8		Cs2CO3 (2.0)	110 °C, 16 h	0
9		NaOtBu (1.5)	90 °C, 16 h	31
10		NaOtBu (2.0)/TBAB (1.0)	90 °C, 16 h	22
11		NaOtBu (2.0)	μW, 90 °C, 1 h	72
12		NaOtBu (2.0)	μW, 80 °C, 2 h	35
13c		NaOtBu (2.0)	μW, 90 °C, 1 h	83
14d		NaOtBu (2.0)	μW, 90 °C, 1 h	(79)

^aConditions: 2a (0.10 mmol), 3a (0.15 mmol), Pd(OAc)₂ (0.010 mmol), ligand (0.020 mmol), base (0.20 mmol), toluene (1.5 mL), under the indicated conditions.

^bDetermined by ¹H NMR using triethylphosphate as internal standard. Isolated yield is in parentheses.

^cIn 1.0 mL of toluene.

^dOn a 0.20 mmol scale with Pd(OAc)₂ (0.010 mmol, 5 mol%) in 2.0 mL of toluene. TBAB = tetrabutylammonium bromide.