methanesulfonyl chloride; triethylamine in dichloromethane T=0 - 20°C; 5 h;

1: tri-n-butyl-tin hydride With n-butyllithium; diisopropylamine in tetrahydrofuran; hexane T=0°C; 0.5 h; 2: tert-butyl 4-oxo-piperidine-1-carboxylate in tetrahydrofuran; hexane T=-78°C; 2 h; 3: With methanesulfonyl chloride; triethylamine in tetrahydrofuran; hexane T=-78 - 20°C; 15 h;