1-(3-Pyridinyl)-1-ethanone hydrazone (Preparation 76, 0.69 g, 5.3 mmol) was dissolved in dioxan (30 ml) and manganese dioxide (0.85 g, 5.3 mmol) was added portionwise followed by a saturated solution of potassium hydroxide in ethanol (0.5 ml). The reaction mixture was stirred at room temperature for 1.5 h and then filtered through a pad of Celite®. To half of the filtrate was added 1-(3-phenylpropyl)-1H-pyrrole-2,5-dione (Preparation 80, 0.57 g, 2.6 mmol) and the reaction mixture was heated to 90° C. for 7 h and then cooled to room temperature for 16 h. The reaction mixture was heated under reflux for 16 h and then cooled to room temperature for 72 h before concentrating in vacuo. The reaction mixture was purified by chromatography using silica gel (30 g) eluting with dichloromethane:0.880 ammonia (99:1) and then dichloromethane:methanol:0.880 ammonia (97:2:1) to afford the title compound as an oil (230 mg, 28%).
