Hydrazine Monohydrate

• 1-Phenylpropargyl Alcohol [P0220]
• Hydrazine Monohydrate [H0172]
• Trifluoroacetic Acid (= TFA) [T0431]
• Methanol

Trifluoroacetic acid (0.355 mL, 4.64 mmol, 11.6 eq.) was added to a solution of 1-Phenylpropargyl alcohol (52.9 mg, 0.40 mmol) and hydrazine monohydrate (500 mg, 10.0 mmol, 25 eq.) in methanol (5 mL) at room temperature. An RVC electrode was immersed in the solution and constant current electrolysis was performed at a current of 40 mA until an electrical flow of 45 F/mol was completed. Water (20 mL) was added to the reaction mixture and the aqueous layer was extracted with diethyl ether (20 mL, twice). The combined organic layer was dried over sodium sulfate and filtered. The solvent was removed under reduced pressure to give 1-phenyl-1-propanol as a colorless liquid (57.2 mg, >99% yield).

The reaction mixture was monitored by UPLC.
The experiment was conducted in a fume hood because gas is produced during the reaction.
The reaction was carried out for about 8 hours.
IKA ElectraSyn 2.0 was used as an electrolytic apparatus in this experiment.

1-phenyl-1-propanol

¹H NMR (400 MHz, CDCl₃); δ 7.39–7.26 (m, 5H), 4.59 (t, J = 6.4 Hz, 1H), 2.07 (br s, 1H), 1.88–1.70 (m, 2H), 0.92 (t, J = 7.2 Hz, 3H).

• eHydrogenation: Hydrogen-free Electrochemical Hydrogenation
  • C. Russo, M. C. Leech, J. M. Walsh, J. I. Higham, L. Giannessi, E. Lambert, C. Kiaku, D. L. Poole, J. Mason, C. A. I. Goodall, P. Devo, M. Giustiniano, M. Radi, K. Lam, Angew. Chem, Int. Ed. 2023, 62, e202309563.

• 1,3-Diphenyl-1,3-propanedione [D0910]
• Hydrazine Monohydrate [H0172]
• EtOH

Hydrazine monohydrate (275 mg, 5.5 mmol, 1.1 eq.) was added to 1,3-diphenyl-1,3-propanedione (1.12 g, 5.0 mmol) in EtOH (20 mL) at room temperature. The mixture was refluxed for 2 hours.Then water (80 mL) was added to the reaction mixture and precipitate was filtered to give 3,5-diphenyl-1H-pyrazole as a white solid (1.05 g, 95% yield).

The reaction mixture was monitored by UPLC.

3,5-Diphenyl-1H-pyrazole

¹H NMR (400 MHz, DMSO-d₆); δ 7.83-7.75 (m, 4H), 7.43-7.38 (m, 4H), 7.34-7.25 (m, 2H), 7.14 (s, 1H).

• A New Model for Dioxygen Binding in Hemocyanin. Synthesis, Characterization, and Molecular Structure of the μ-η²:η² Peroxo Dinuclear Copper(II) Complexes, [Cu(HB(3,5-R₂pz)₃)]₂(O₂) (R = i-Pr and Ph)
• N. Kitajima, K. Fujisawa, C. Fujimoto, Y. Morooka, S. Hashimoto, T. Kitagawa, K. Toriumi, K. Tatsumi, A. Nakamura, J. Am. Chem. Soc. 1992, 114, 1277.

• 4-Phenyl-3-butyn-2-one [P1336]
• Hydrazine Monohydrate [H0172]
• Ethanol

Hydrazine monohydrate (0.267 mL, 5.5 mmol, 1.1 eq.) was added to a solution of 4-phenyl-3-butyn-2-one (0.707 mL, 5.0 mmol) in EtOH (20 mL) at room temperature and the mixture was refluxed for 4 hours. Then the solvent was removed under reduced pressure and the residue was purified by column chromatography (on silica gel, ethyl acetate:hexane = 0:1 - 1:1) to give 5-methyl-3-phenyl-1H-pyrazole as a pale yellow solid (684 mg, 86% yield).

The reaction mixture was monitored by UPLC.

5-Methyl-3-phenyl-1H-pyrazole

¹H NMR (400 MHz, CDCl₃); δ 7.71 (d, J = 8.0 Hz, 2H), 7.37 (t, J = 7.2 Hz, 2H), 7.32-7.28 (m, 1H), 6.35 (s, 1H), 2.30 (s, 3H).

• Direct synthesis of pyrazoles from esters using tert-butoxide-assisted C-(C=O) coupling
• B. R. Kim, G. H. Sung, K. E. Ryu, S.-G. Lee, H. J. Yoon, D.-S. Shin, Y.-J. Yoon, Chem. Commun. 2015, 51, 9201.