To a mixture of methyl 5-bromo-3-methyl-1-benzofuran-2-carboxylate (6.06 g) synthesized above, zinc cyanide (2.64 g) and N,N-dimethylformamide (60 mL) was added tetrakis(triphenylphosphine)palladium (0) (1.31 g), and the mixture was deaerated and stirred under argon atmosphere at 80° C. overnight. Water was added to quench the reaction, and the mixture was extracted with ethyl acetate. The extract was washed with saturated brine, dried over magnesium sulfate, and concentrated under reduced pressure. The residue was washed with diisopropyl ether to give the title object compound (4.20 g, 87%) as a pale-brown solid.
