4-(N,N-dimethlyamino)pyridine in dichloromethane 0.5 h;

1: sodium carbonate / benzene / 5 h / Heating 2: 100 percent / 3,5-bis(ethoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine, silica gel / benzene / 0.5 h / Heating View Scheme

potassium hydroxide