1: 3,4-dichloropyridine With n-butyllithium; diisopropylamine in tetrahydrofuran; hexane T=-75°C; 2 h; 2: carbon dioxide T=-78°C;

1: 3,4-dichloropyridine With 2,2,6,6-tetramethyl-piperidine; n-butyllithium in diethyl ether; hexane T=-75°C; 2 h; 2: carbon dioxide T=-78°C;

1.1: butyllithium; diisopropylamine / tetrahydrofuran; hexane / 2 h / -75 °C 1.2: 76 percent / 1,1,2-trichloro-1,2,2-trifluoroethane / tetrahydrofuran; hexane / 1 h / -75 °C 2.1: 2,2,6,6-tetramethylpiperidine; butyllithium / diethyl ether; hexane / 2 h / -75 °C 2.2: -78 °C View Scheme