Optimization of reaction conditions^a.

Entry	CpR	Base	Solvent	Yieldb (%)
1	Cp*	TMPH	DCE	31
2	Cp*	PMP	DCE	Trace
3	Cp*	i-Pr2NEt	DCE	Trace
4	Cp*	Pyridine	DCE	0
5	Cp*	2,6-Lutidine	DCE	34
6	Cp*	sym-Collidine	DCE	62
7	Cp	sym-Collidine	DCE	10
8	CpR1	sym-Collidine	DCE	14
9	CpR2	sym-Collidine	DCE	20
10	Cp*	sym-Collidine	CHCl3	60
11	Cp*	sym-Collidine	PhCl	70
12	Cp*	sym-Collidine	PhCF3	83
13c	Cp*	sym-Collidine	PhCF3	77 (72d)
14e	Cp*	sym-Collidine	PhCF3	56

^aAll reactions were carried out with 1a (0.1 mmol), 2a (1.5 equiv.), Ph₃C⁺BF₄⁻ (1.7 equiv.), base (1.8 equiv.) and 30 mol% of iron catalyst in solvent (0.5 mL).

^bNMR yield.

^c20 mol% of iron catalyst.

^dIsolated yield.

^e10 mol% iron catalyst. DCE = 1,2-dichloroethane. PMP = 1,2,2,6,6-pentamethylpiperidine. sym-Collidine = 2,4,6-collidine. Cp* = pentamethylcyclopentadienyl. Cp^R1 = 1,3-(t-Bu)₂cyclopentadienyl, Cp^R2 = tetramethylcyclopentadienyl.