1: 1) n-butyllithium / 1) diethyl ether, -30 deg C, 1h, 2) <-50 deg C 2: 64 percent / ethyllithium / diethyl ether / 0.5 h / -55 °C View Scheme

1: 3-bromo-2-methyl-5-methyl-thiophene With n-butyllithium in tetrahydrofuran; hexane T=-78°C; 0.25 h; Inert atmosphere; 2: tributoxyborane in tetrahydrofuran; hexane T=-78 - 20°C; Inert atmosphere;

1: With n-butyllithium in tetrahydrofuran 2: With tributoxyborane 3: With hydrogenchloride

carbon disulfide; bromine