Table 1. Optimization of Reaction Conditions for the Pd-Catalyzed Cross-Coupling of s-BuB(OH)2 and 4-Chloroanisole.
| entry | variations from above | yield (%)a | 2:3a |
|---|---|---|---|
| 1 | none | 98 | >200:1 |
| 2 | 2 mol % P(t-Bu)3 precatalyst | 98 | 36:1 |
| 3 | 2 mol % Pd(dba)2, 2 mol % P(t-Bu)3·HBF4 | 70 | 36:1 |
| 4 | Cs2CO3 (3 equiv) instead of K2CO3 | <5 | – |
| 5 | K3PO4-H2O (3 equiv) instead of K2CO3 | 94 | 69:1 |
| 6 | 5 mol % n-BuP(Ad)2 precatalyst | 89 | 4:1 |
| 7 | 5 mol % PhP(t-Bu)2 precatalyst | 94 | 32:1 |
| 8 | toluene/H2O(1:2) | 89 | 70:1 |
| 9 | THF instead of toluene | <5 | – |
| 10 | dioxane instead of toluene | <5 | – |
| 11 | methylcylcohexane instead of toluene | 97 | >200:1 |
a
Yields and selectivities determined by GC.