. 2011 Jul 19;7:988–996. doi: 10.3762/bjoc.7.111

Table 2.

Optimization of the 1,3-dipolar cycloaddition of 6a and tert-butyl acrylate using chiral (S_a)-BINAP (13) ligand.

Entry	Catalyst^a	Base	Yield^b (%)	ee^c (%)

1	(S_a)-13/AgClO₄	Et₃N	78	88
2	(S_a)-13/AgClO₄	Et₃N^d	75	85
3	(S_a)-13/AgSbF₆	Et₃N	79	72
4	(S_a)-13/AgTFA	Et₃N	82	40
5	(S_a,S_a)-14	^___	^___e	^___e
6	(S_a,S_a)-14	Et₃N	90	78
7	(S_a,S_a)-14	DIPEA	87	70
8	(S_a,S_a)-14	Et₃N^d,f	92	99

^aThe generation of silver catalysts was achieved by mixing equimolar amounts of silver(I) and (S_a)-BINAP. ^bAfter flash chromatography (silica gel). The observed endo:exo ratio was always >98:2 (¹H NMR). ^cDetermined using analytical chiral HPLC columns (Daicel, Chiralpak AS). ^dReaction performed at 0 °C. ^eNot determined. ^fAfter 3 days reaction.