Table 4. Comparison of catalytic performance among 1a, 2a, and other common carbene transfer catalysts ^a .

Entry	Catalyst	Yield of 5a b (%)
1	1a	90
2	[FeII(TPFPP)]	48
3	2a	92
4	[Rh2(esp)2]	10
5	CuI	1
6	[Ru(TTP)(CO)]	56

^aConditions: Ph₂CN₂ (0.2 mmol), styrene (2 mmol), catalyst (0.004 mmol), DCM (1 mL), 40 °C, 12 h, and under Ar.

^bYield determined by ¹H NMR with PhTMS as the internal standard.