Table 1.

On the Unique Nature of Silanediol 1a-Cu(OTf)₂ Hybrid Catalysis^a

Entry	HBDb	Lewis Acid	Yield (%)	ee (%)
1	1a	Cu(OTf)2	92	72
2	1a	Sc(OTf)3	95	9
3	1a	In(OTf)2	88	10
4	1a	CuOTf	10	31
5	1a	CuCl	0	--
6	1a	CuSO4	0	--
7	1b	Cu(OTf)2	76	13
8	1c	Cu(OTf)2	14	6
9	10	Cu(OTf)2	0	--
10	11	Cu(OTf)2	0	--
11	12	Cu(OTf)2	10	10
12	17	Cu(OTf)2	28	racemic
13	18	Cu(OTf)2	25	racemic

^aSee the experimental sections for details of the procedures.

^bHBD = hydrogen bond donor.