Table 1. Catalyst Screening with 1-Bromo-3,5-dimethoxybenzene (1) and 3-Ethynylpyridine (2)a.
entry | catalyst | 3 (yield, %)b |
---|---|---|
1 | Pd(PPh3)2Cl2, CuI | 0c |
2 | P1 | 52 |
3 | P2 | 75 |
4 | P3 | 0 |
5 | P4 | 57 |
6 | P5 | 53 |
7 | P6 | 0 |
8 | P7 | 0 |
9 | P8 | 27 |
10 | P9 | 23 |
11 | P10 | 63 |
12 | P11 | 56 |
13 | P12 | 0 |
14 | P13 | 4 |
15 | P14 | 1 |
16 | P15 | 0 |
17 | P6 with L1 (1:1) | 84d |
18 | P7 with L1 (1:1) | 78d |
19 | P2 with L1 (1:1) | 71d |
20 | P2 | 2e |
Reaction conditions: 1 (0.5 mmol), 2 (0.8 mmol), cat. (.025 mmol), DABCO (1.0 mmol), THF (2.5 mL), rt for 18 h under argon atmosphere.
Yield was determined by liquid chromatography/mass spectrometry (LC/MS) with pyrene as internal standard.
Followed standard Sonogashira reaction procedure.
Catalyst and ligand stirred for 5 min prior to reagent addition.
Without degassing using argon or nitrogen.