1: (4-fluoro-phenyl)-carbamic acid tert-butyl ester With tert.-butyl lithium in tetrahydrofuran T=-78 - -25°C; 2.5 h; 2: tert-butyl 4-oxo-piperidine-1-carboxylate in tetrahydrofuran T=-78°C; 4 h; 3: With potassium tert-butylate in tetrahydrofuran T=-78 - 20°C; 18 h;

1: (4-fluoro-phenyl)-carbamic acid tert-butyl ester With n-butyllithium in tetrahydrofuran; hexane T=-70 - -20°C; 3.33333 h; 2: 2-(3,4-dichloro-phenyl)-4-oxo-butyric acid methyl ester With potassium tert-butylate in tetrahydrofuran; hexane T=-60 - 20°C; 14 h;