Table 1. The discovery and initial optimization of monodefluorination reaction.

Entry a	Catalyst	Base	2	3	Conversion
1	Pd(OAc)2 1 mol%	KOt-Bu	94%	0%	100%
2 b	Pd(OAc)2 1 mol%	NaOt-Bu	8%	7%	—
3 b	Pd(OAc)2 1 mol% & SIPrCuCl 1 mol%	NaOt-Bu	12%	52%	90%
4 c	Pd(OAc)2 3 mol% & SIPrCuCl 20 mol%	NaOt-Bu	15%	51%	100%
5 c	Pd(OAc)2 3 mol% & SIPrCuCl 20 mol% & 2-pyridone 5 mol%	NaOt-Bu	3%	56%	100%

^aReaction conditions: Ph₃SiH (4 equiv.), base (5 equiv.), DMF, 25 °C, 1 h.

^bReaction performed at 45 °C for 11 h then 60 °C for 17 h.

^cReaction performed at 45 °C for 2 h, followed by 60 °C for 17 h. Ar = 4-(4-CH₃Ph)C₆H₄; SIPr = N,N′-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene; DMF = N,N-dimethylformamide. All yields were determined by GC using an internal standard.