To a flame-dried 250-mL round-bottomed flask equipped with a magnetic stir bar was added ketone 4-3 (16.4 g, 129 mmol, 1.0 equiv) and MeCN (65 mL, 2.0 M). To the stirred reaction mixture was added Böhme's salt 4-6 (13. 3 g, 142 mmol, 1.1 equiv). The reaction vessel was fitted with an oven-dried reflux condenser, and the reaction apparatus was transferred to an 80 °C pre-warmed oil bath. After stirring at 80 °C for one hour, the reaction apparatus was removed from the oil bath and allowed to cool to room temperature. Once at room temperature, the reaction mixture was concentrated under reduced pressure by rotary evaporation to provide 3-3 as a colorless solid, which was used without further purification (25. 1 g, 88%) To a flame-dried 250-mL round-bottomed flask equipped with a magnetic stir bar was added diketone 3-2 (12.0 g, 95.1 mmol, 1.0 equiv) and EtOH (190 mL, 0.5 M). To the stirred reaction mixture was added ammonium salt 3-3 (25. 1 g, 114 mmol, 1.2 equiv) and ammonium acetate (22.0 g, 285 mmol, 3.0 equiv). The reaction vessel was fitted with an oven-dried reflux condenser, and the reaction apparatus was transferred to an 80 °C pre-warmed oil bath.