1: 1.) n-BuLi, 2.) BF3*OEt2 / 1.) THF, -78 deg C, 30 min, 2.) -78 deg C, 90 min 2: 1.) copper(I) cyanide, 2.) trimethylsilyl chloride / 1.) ether, from -40 to -78 deg C, 1.5 h, 2.) -78 deg C, 2 h View Scheme

chloro-trimethyl-silane; copper (I) cyanide 1.) ether, from -40 to -78 deg C, 1.5 h, 2.) -78 deg C, 2 h; Yield given. Multistep reaction. Yields of byproduct given;