Table 2. Optimization of the reaction conditions^a.

Entry	1	Cat.	Yield (%)b	ee (%)c	drd
1	1a	—	29	0	1.5 : 1
2	1v	—	32	0	10 : 1
3	1a	C6	83	0	1.2 : 1
4	1v	C6	80	2	10 : 1
5	1v	CP1	79	44	11.5 : 1
6	1v	CP2	72	7	9 : 1
7	1v	CP3	82	63	7 : 1
8	1v	CP4	74	47	4.5 : 1
9	1v	CP5	77	83	4 : 1

^aReaction conditions: 1v (0.025 mmol), 4a (0.025 mmol), catalyst (10 mol%) in toluene (0.25 mL), and 5 Å MS(25 mg) at 0 °C for 3 h.

^bIsolated yield.

^cee determined by chiral HPLC analysis.

^ddr determined by crude ¹H NMR analysis.