Table 2. Cyclocarbonylative Sonogashira Coupling Reactions of 2-Iodophenol (1a) with Phenylacetylene (2a)a,b.
| selectivity
(%)c |
||||
|---|---|---|---|---|
| no. | catalyst (mol %) | conv. (%)c | 3aa (%)d | 4aa (%)d |
| 1 | C1 (0.5%) | 98 | 96 (92) | 4 |
| 2 | C2 (0.5%) | 88 | 96 (85) | 4 |
| 3 | C3 (0.5%) | 84 | 95 (79) | 5 |
| 4e | Pd–NHC–Py1 (0.05%) | 83 | 89 (77) | 11 |
| 5e | Pd–NHC–Py2(0.5%) | 79 | 86 (72) | 14 |
| 6 | Pd(OAc)2 (0.5%) L1 (0.5%) | 81 | 94 (75) | 6 |
| 7 | Pd(OAc)2 (5%) DPPF (10%) | 100 | 88 (85) | 12 |
| 8f | Pd(OAc)2 (5%) DPPF (10%) | 95 | 50 (46) | 50 (45) |
| 9 | Pd(OAc)2 (0.5%) | 38 | 89 (32) | 11 |
| 10 | PdBr2 (0.5%) | 29 | 89 (24) | 11 |
| 11 | PdCl2(PPh3)2 (0.5%) | 60 | 86 (49) | 14 |
| 12 | Pd/C (10%) | 90 | 92 (81) | 8 |
a
Effect of the type of catalyst.
b
Reaction conditions: [Pd] (mol %), 2-iodophenol (0.5 mmol), phenylacetylene (0.6 mmol), Et2NH (1.0 mmol), DMF (2.5 mL), CO (100 psi), 100 °C, 16 h.
c
Determined by GC and GC–MS.
d
Isolated yield.
e
Heteroleptic N-heterocyclic carbene palladium(II) complexes (Pd–NHC–Py).59
f
THF was used as a solvent.