formic acid; [{(η5-C5Me5)RhCl}2(μ-Cl)2]; triethylamine; N-(2-amino-ethyl)-4-methyl-benzenesulphonamide in ethyl acetate T=28°C; 3 h; chemoselective reaction;

diethyl-1,4-dihydro-2,6-dimethyl-3,5-pyridine dicarboxylate; silica gel in benzene T=60°C; 20 h;

1: triethylamine / 17 h 2: pyridine / 2 h / Ambient temperature 3: sodium carbonate / benzene / 5 h / Heating 4: 83 percent / 3,5-bis(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine, silica gel / benzene / 0.5 h / Heating View Scheme

NSC26899 in acetonitrile T=80°C;

1: pyridine / 2 h / Ambient temperature 2: sodium carbonate / benzene / 5 h / Heating 3: 83 percent / 3,5-bis(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine, silica gel / benzene / 0.5 h / Heating View Scheme

1: 78 percent / NaNO2, NaOH / methanol / 0 °C 2: Et3N / CH2Cl2 / Ambient temperature 3: 81 percent / Bu3SnH, AIBN / benzene / Heating View Scheme