1: 1.) O3, 2.) Me2S / 1) MeOH, -78 deg C; 2) MeOH, rt, 1 h 2: 22 percent / Li, TiCl4, TMSCl, air / tetrahydrofuran / 24 h / Heating View Scheme

dimethylsulfide; ozone 1) MeOH, -78 deg C; 2) MeOH, rt, 1 h; Yield given. Multistep reaction;