1-(phenylhydrazinylidene)propan-2-one

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To 2-oxopropanal phenylhydrazone (5.00 g, 30.8 mmol) in acetic acid (60 mL) was added a 40% aqueous solution of glyoxal (5.9 g, 4.6 mL, 30.8 mmol) and the mixture was heated at reflux for 45 minutes. The acetic acid was removed under reduced pressure. The resultant mixture was diluted with ethyl acetate (100 mL), washed with NaHCO3 and sat. aq. NaCl. Solids were removed by filtration, the filtrate was dried over Na2SO4, filtered and concentrated. The crude material was purified by CombiFlash (180 g column, 0-20 EtOAc/heptane gradient) to afford 1-(4-hydroxy-1-phenyl-1H-pyrazol-3-yl)ethanone as a yellow solid (2.70 g, 43%). the mixture was heated at reflux for 45 minutes The acetic acid was removed under reduced pressure The resultant mixture was diluted with ethyl acetate (100 mL) washed with NaHCO3 and sat. aq. NaCl Solids were removed by filtration the filtrate was dried over Na2SO4 filtered concentrated The crude material was purified by CombiFlash (180 g column, 0-20 EtOAc/heptane gradient)

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of phenylhydrazine (10.0 g, 92.5 mmol) in water (30 mL) was added acetic acid (8.8 mL) followed by the dropwise addition of pyruvaldehyde (16.7 g, 92.5 mmol) in water (400 mL) over a 15 minute period. The solution was stirred at room temperature overnight. The reaction was filtered and the resultant solid was washed with water (2×30 mL) to provide 2-oxopropanal phenylhydrazone as a yellow solid (15.2 g, 101%). The reaction was filtered the resultant solid was washed with water (2×30 mL)