Tritch, K. J.; Capek, J. A.; Klein, N. D.; Noland, W. E. ChemSpider Synthetic Pages 2017, 815, 1.
Ketone (2–3 g), CH2Cl2 (80 mL), and MgSO4 (2.0 eq.) were combined in a round-bottomed flask, with magnetic stirring. Phenylhydrazine (2.0 eq.), and then toluene-4-sulfonic acid monohydrate (4–7 mol%) were added. The resulting orange-colored mixture was refluxed for 24 h in an N2 atmosphere, allowed to cool to room temperature, and then filtered. The filtrate was washed with NaHCO3 solution (aq., sat., 30 mL), and then brine (30 mL). The organic portion was dried with MgSO4, filtered, and then concentrated on a rotary evaporator. The resulting brown residue was recrystallized from toluene, washed with pentane, and then dried under vacuum (0.1 mm Hg, 97 ºC, 4 h), giving yellow flakes.