Table 1. Optimization of the Reaction Conditionsa.
| yield (%) |
|||||
|---|---|---|---|---|---|
| entry | [M] cat. | ligand (mol %) | 4aab | 5aab | 6aab |
| 1 | Rh2(Oct)4 | – | 74 | 31 | 0 |
| 2 | Rh2(Oct)4 | BINAP (1.5) | 75 | 26 | 3 |
| 3 | Rh2(Oct)4 | Xantphos (1.5) | 76 | 7 | 18 |
| 4 | Rh2(Oct)4 | dppb (1.5) | 86 | 0 | 5 |
| 5 | Rh2(Oct)4 | PPh3 (3.0) | 86 | 8 | 0 |
| 6 | Rh2(Oct)4 | iPr-NHCc (3.0) | 53 | 4 | 15 |
| 7 | Rh2(TPA)4 | Xantphos (1.5) | 91 | 0 | 12 |
| 8 | Rh2(OPiv)4 | Xantphos(1.5) | 42 | 0 | 85 |
| 9 | CuCl | Xantphos (1.5) | 27 | 0 | 0 |
| 10 | [Pd(PhCN)2Cl2] | Xantphos (1.5) | 99 | 0 | 0 |
| 11 | Rh(COD)2BF4 | Xantphos (1.5) | 99 | 0 | 0 |
| 12 | – | Xantphos (1.5) | 0 | 0 | 0 |
a
1a (0.375 mmol, 1.5 equiv), 2a (0.25 mmol, 1.0 equiv), 3 (0.75 mmol, 3.0 equiv), MeCN (2.0 mL), [M] catalyst (1.0 mol %), ligand (1.5 mol %), Cs2CO3 (3.5 equiv), 60 °C, 6.0 h.
b
GC yields. Yields for 4aa were calculated based on 1a as the limiting substrate. Yields for 5aa and 6aa were calculated based on 2a as the limiting substrate.
c
iPr-NHC = 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride.