Table 2. Optimization of reaction conditions for the gold-catalyzed cycloisomerization of 2a.
| ||||||
|---|---|---|---|---|---|---|
| Entry | Catalyst (3 mol%) | Solvent | Temperature (°C) | Yielda (%) | ||
| 4a | 5a | 6a | ||||
| 1b | [JohnPhosAu(MeCN)]SbF6 | DCM | rt | N.D. | 37 | 54 |
| 2 | JohnPhosAuOAc | DCE | rt | N.R. | ||
| 3 b | [JohnPhosAu(MeCN)]SbF 6 | DCM | 0 | Trace | 84 | <5 |
| 4 | IPrAuNTf2 | DCE | 80 | N.D. | N.D. | 90 |
| 5 | [JohnPhosAu(MeCN)]SbF 6 | DCE | 60 | N.D. | N.D. | 95 |
| 6b | [JohnPhosAu(MeCN)]SbF6 | DCM | −20 | 5d | Trace | N.D. |
| 7 b , c | IPrAuNTf 2 | DCM | −30 | 75 | Trace | N.D. |
a
Isolated yield.
b
The reaction was quenched with DMS (dimethyl sulfide).
c
The reaction was conducted for 8 hours.
d
NMR yield.