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| Entry | Base | Mono-substituted intermediate | DIT yield (η%) |
|---|---|---|---|
| 1 | Cs2CO3 | Present | 89 |
| 2 | NaHCO3 | Present | 78 |
| 3 | KHCO3 | Present | 82 |
| 4 | NaOH | Absent | 88 |
| 5 | KOH | Absent | 91 |
Reaction conditions: 2,5-dibromothiophene 0.2 M; solvent mixture 1,4-dioxane/H2O (2 : 1); boronic ester 1.5 eq.; Pd(PPh3)4, catalyst 1.5 mol%; base 4 eq.; temperature 90 °C; time 24 h; argon atmosphere.
