1: With oxalyl dichloride; dimethyl sulfoxide in dichloromethane T=-78°C; 1 h; 2: 4-fluoro-4-hydroxymethyl-piperidine-1-carboxylic acid tert-butyl ester in dichloromethane T=-78°C; 1.5 h; 3: With triethylamine in dichloromethane T=20°C; 1.5 h;