Synthesis of new 2-E-3,5-dihalothiophenes

2-Substituted 3,5-dihalothiophenes, general procedure

To a well stirred solution of diisopropylamine (4.46 mmol) in anhydrous THF (10 ml) under N2 at -40 C, BuLi (4.46 mmol) is added dropwise and stirrring is continued for 25 min at -40 C. Then a solution of the 2,3-dihalothiophene (4.05 mmol) in anhydrous THF (5 ml) is added rapidly at -40 C and stirring is continued for 60 min at -40 C. The intermediate thus formed is trapped by (slow) addition of the electrophile in THF (5 ml) and stirring is continued for 30 min at -40 C. The mixture is then allowed to warm to 0 C and poured into water. The aqueous layer is extracted with diethyl ether, the combined organic layers are washed with water and dried (MgSO4). The solvent is removed and the residue is either distilled under reduced pressure (kugelrohr) or filtered over a short silica-column.