Table 1.

Reaction development and the control experiment^a

Entry	Derivation from standard condition	Yields of 3a (%)	Yields of recovered donor (%)	Yields of 4 (%)
1	None	96	-	99
2	No Sc(OTf)3	0	>95	0
3	Bi(OTf)3 as the catalyst	65	40	58
4	Zn(OTf)2 or Ca(OTf)2/nBu4NPF6 or B(C6F5)3 as catalyst	0	>95	0
5	TfOH as catayst	complex mixture	-	NA
6	TMSOTf as catalyst	<5	>95	<5
7	Ph3PAuNTf2 as catalyst	0	>95	0
8	4 Å MS instead of 5 Å MS	33	68	30
9	CH2Cl2 as the solvent	99	-	99
10	PhCH3 or PhCF3 or Et2O as solvent	96–97	-	>95
11b	glucose pentabenzoate 5 as donor	trace	>95	NA

^aUnless otherwise specified, all reactions were performed with 1.2 equiv of 1a, 1.0 equiv of 2a (0.05 mmol) in the presence of the catalyst (0.1 equiv) and 5 Å MS in corresponding solvent (0.05 M, 1 mL) for 2–5 h at room temperature. The yield for 3a was based on 2a, and the yields for 4 and the recovered donor were based on the 1a. ^bCH₂Cl₂ was used as the solvent. Bz Benzoyl, Me Methyl, Tf Trifluoromethanesulfonyl, DCE 1,2-dichloroethane, ⁿBu n-Butyl, TMS Trimethylsilyl, Ph Phenyl, MS Molecular sieve, Et Ethyl, NA Not applicable.