Glyoxal → 1-(1-benzyl-4-hydroxy-1H-pyrazol-3-yl)ethanone

Reaction equation

[CH:1]([CH:3]=O)=[O:2].[CH2:5]([NH:12][N:13]=[CH:14][C:15](=[O:17])[CH3:16])[C:6]1[CH:11]=[CH:10][CH:9]=[CH:8][CH:7]=1>O.CO>[CH2:5]([N:12]1[CH:16]=[C:15]([OH:17])[C:14]([C:1](=[O:2])[CH3:3])=[N:13]1)[C:6]1[CH:11]=[CH:10][CH:9]=[CH:8][CH:7]=1

Participants

Procedure

To a 40% aqueous solution of glyoxal (8.28 g, 6.55 mL, 57.1 mmol) was added a slurry of 2-oxopropanal benzylhydrazone (10.1 g, 57.1 mmol) in water (250 mL) and methanol (25 mL). The resulting mixture was heated at reflux for 3 hours before cooling to room temperature. The mixture was extracted with EtOAc (2×100 mL) and the combined organic extracts were washed with water, saturated aqueous NaCl, dried over Na2SO4, filtered and concentrated. The crude material was purified by CombiFlash (120 g column, 0-100% EtOAc/heptane gradient) to provide 1-(1-benzyl-4-hydroxy-1H-pyrazol-3-yl)ethanone (4.07 g, 33%).