Exploration of the cycloaddition of 1b; selectivity with different Au and Pt catalystsa.
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| Entry | [M] | T (°C) | t (h) | 4b : 3b ratiob | Yieldc (%) |
| 1 | IPrAuCl/AgSbF6 (Au1) | rt | 2 | 5 : 1 | 70 (4b) |
| 2 | JohnPhosAuNTf2 (Au2′) | rt | 12 | — | —d |
| 3 | XPhosAuNTf2 (Au4)e | 80 | 12 | 1.1 : 1 | 18 (4b) |
| 4 | RuPhosAuNTf2 (Au5) | 40 | 12 | 16 : 1 | 32 (4b) |
| 5 | IPrMeAuCl/AgNTf2 (Au6) | rt | 2 | 1 : 0 | 96 (4b) |
| 6 | (ArO)3PAuCl/AgSbF6 (Au3)f | −15 | 1.5 | 1 : 7 | 66 (3b) |
| 7 | (C6F5)3PAuCl/AgNTf2 (Au7)g | −15 | 1 | 1 : 12 | 70 (3b) |
| 8 | AuCl3 | rt | 12 | — | —d |
| 9 | AuBr3 | rt | 12 | — | —d |
| 10h | PicAuCl2 | 110 | 8 | 1 : 0 | 17 (4b) |
| 11h | PtCl2 | 110 | 0.5 | 1 : 0 | 43 (4b) |
| 12h | [PtCl2(ethene)2]2g | 110 | 1 | 1 : 0 | 53 (4b) |
| 13h | PtCl2/(C6F5)3P (1 : 1) | 110 | 1 | 1 : 0 | 62 (4b) |
| 14h | PtCl2 | 70 | 2 | 1 : 0 | 81 (4b) |
| 15i | PtCl2 | 50 | 2 | 1 : 0 | 88 (4b) |
| 16j | PtCl2 | 30 | 2.5 | 1 : 0 | 99 (4b) |
| 17j | PtCl2 (1 mol%) | 30 | 24 | 1 : 0 | 92 (4b) |
a
Carried out with [M] (10 mol%) in CH2Cl2 (0.05 M), unless otherwise noted. See Tables S1–S2 for the structures of Au complexes and further examples.
b
Ratio determined by 1H-NMR of the crude mixtures.
c
Isolated yield.
d
Complex mixture of products.
e
Carried out in 1,2-DCE.
f
Ar = 3,5-(tBu)2C6H3.
g
Carried out with 5 mol% catalyst.
h
Carried out in toluene.
i
Carried out in cyclohexane (with 1 ppm of water).
j
Carried out in 1,4-dioxane.