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
11^b	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.

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