Preparation
3,5-diethyl-1,2-dihydro-1-phenyl-2-propylpyridine (DHP) was prepared using methods shown below. A 1000 mL four neck flask was equipped with a mechanical stirrer, a reflux condenser, a thermometer, and an addition funnel. An ice-water bath was used to cool the flask as needed. The flask was charged with 86 g de-ionized water, 9.8 g (0.16 mole) acetic acid, and 216 g (3.0 mol) butyraldehyde. With cooling and stirring, 60 g (0.64 mole) aniline was added over a 35-minute period while maintaining the reaction temperature at 20℃. The reaction mixture was stirred for one hour at less than 25℃. The reaction mixture was then heated to 750C and held for two hours. Finally, the reaction mixture was heated to reflux (~90°C) and was held for five hours. The reaction mixture was cooled and the layers were separated. The top, organic layer was distilled through a 14" packed column under reduced pressure. The fraction taken at a head temperature of 140-1430C and 5 mm Hg pressure weighed 104 grams and was analyzed to contain 73% DHP for an overall yield of 46%.
