To a solution of 3-(tert-butoxycarbonyl)amino-5-bromo-thiophene-2-carboxylic acid methyl ester (4.566 g, 13.58 mmol) in dry DMF (40 mL) are added copper (I) iodide (52 mg, 0.27 mmol), Pd2 dba3 (622 mg, 0.68 mmol) and triethylamine (9.46 mL, 67.9 mmol), and the mixture is deoxygenated by bubbling nitrogen through solution for 10 min. Then tert-butylacetylene (6.62 mL, 54.32 mmol) and BINAP (676 mg, 1.09 mmol) are added to the mixture, and it is heated at 60° C. overnight under nitrogen. The mixture is diluted with CH2Cl2 and filtered through celite washing with CH2Cl2. Filtrate is washed with brine, organic fraction is separated, dried over Na2SO4, concentrated, and the residue is purified by column chromatography on silica gel eluting with gradient of EtOAc in hexane to give of 5-(3,3-dimethyl-but-1-ynyl)-3-(tert-butoxycarbonyl)amino-thiophene-2-carboxylic acid methyl ester.
