copper(I) bromide dimethylsulfide complex; boron trifluoride diethyl etherate in tetrahydrofuran T=-78°C; 3 h;

1: MeLi / tetrahydrofuran / 0.25 h / -78 °C 2: 1)n-Bu3P / 1)CuBr*Me2S / 1)THF, -78 deg C, 20 min 2)-78 deg C, 1h, then -40 deg C, 2 h View Scheme

tributylphosphine; copper(I) bromide dimethylsulfide complex 1)THF, -78 deg C, 20 min 2)-78 deg C, 1h, then -40 deg C, 2 h; Yield given. Multistep reaction;