Table 1.

Optimization of a model U-5C-4CR

Entry	Catalysta	Temperature (°C)	Time (h)	Yield (%)b	drc
1	–	23	12	34	–
2	–	60	12	63	73:27
3	Sc(OTf)3	60	12	72	72:28 (70:30)d
4	TiCl4	60	12	74	73:27
5	Sc(OTf)3	60	24	69	74:26

Reactions were performed on a 0.602 mmol scale in MeOH

^a10 mol%

^bIsolated yields

^cdr values based on HPLC/MS analyses of the crude reaction mixtures

^ddr value based on ¹H NMR analysis of the sample purified by column chromatography on silica