Diethyl bromoterephthalate (45.2 g, 150 mmol), K2CO3 (41.5 g, 300 mmol), 140 ml of toluene and 140 ml of H2O were placed in the reaction vessel and flushed with argon for 30 minutes. 2,5-Dimethylbenzeneboronic acid (24.8 g, 165 mmol) (cf. B3) and Pd(PPh3)4 (0.7 g, 0.6 mmol) were subsequently added under protective gas. The brownish mixture, which was turbid as a result of phase separation, was stirred vigorously under a blanket of protective gas at an internal temperature of 85° C. The reaction was complete after 24 hours (according to TLC). After phase separation, the organic phase was shaken with dilute HCl/H2O (until neutral). The aqueous phase was shaken with toluene and the organic phases were combined. After filtering off any palladium residues, the solution was evaporated. The product was obtained as a yellow oil in satisfactory purity (greater than 97%). Yield: 48.7 g (99%).
