A solution of 2-bromo-5-pentylthiophene (10.0 g), 4-methoxyphenyl boronic acid (7.9 g), 2M aqueous sodium carbonate solution (150 cm3), 2.3 g tetrakis(triphenylphosphine)palladium (0) and dimethoxyethane (100 cm3) was heated under reflux for 6 h. 20% Hydrochloric acid (200 cm3) was added to the cooled reaction mixture and the resultant mixture extracted with diethyl ether (5×100 cm3). The combined organic layers were washed with 20% hydrochloric acid (1×100 cm3), brine (2×100 cm3) and then dried (MgSO4), filtered and evaporated down. The residue was purified by column chromatography on silica gel using a 4:1 hexane/dichloromethane mixture as eluent and recrystallisation from ethanol to yield 8.7 g of 2-(4-methoxyphenyl)-5-pentylthiophene, K 58-60° C., I.
