Table 2.

Optimization studies.^a

entry	catalyst	solvent	temp. (°C)	conv. (%)	3 yield (%)
1	8• (TFA)2	CH3CN	140	65	48
2	8• (TFA)2	DCE	140	49	20
3	8• (TFA)2	MeOH	140	100	40
4	8• (TFA)2	EtOH	140	100	78 (73)b
5	8• (TFA)2	EtOH	120	85	47
6c	TFA	EtOH	140	100	0
7	FeCl3	DCE	rt	100	0

^aConditions: substrate 9i (0.2 mmol) and 10 mol % catalyst in 1.0 mL of solvent in a 5 mL sealed tube were heated to the temperature indicated for 12 h. Conversions and yields were determined by ¹H NMR using CH₂Br₂ as an internal standard.

^bIsolated yield;

^c20 mol % TFA was used.