Reaktion #40775

Reaktionsgleichung

hydrazine hydrate

diethylether

2-Methyl-3-phenyl-propenal

→

desired product

4-Methyl-5-phenyl-4,5-dihydro-1H-pyrazole

Lösungsmittel

H2O

Reaktionsbedingungen

Aufarbeitung

1. 1
   TemperaturThe emulsion was cooled with an ice bath
2. 2
   Sonstigethe organic layer was separated
3. 3
   Extraktionthe aqueous layer was extracted with diethylether
4. 4
   TrocknenThe combined organic layers were dried over Na2SO4
5. 5
   Filtrationfiltrated
6. 6
   Einengenconcentrated in vacuo
7. 7
   workup.DISTILLATIONVacuum distillation

Vorschrift

5.22 ml (1 equiv.) hydrazine hydrate was added to 100 mL diethylether. The emulsion was cooled with an ice bath. 15.0 mL 2-Methyl-3-phenyl-propenal was added dropwise, and the mixture was stirred overnight at room temperature. H2O was added, the organic layer was separated and the aqueous layer was extracted with diethylether. The combined organic layers were dried over Na2SO4, filtrated and concentrated in vacuo. Vacuum distillation yielded 5.9 g of desired product (mixture of diastereomeric pairs) as a clear fluid (76-82° C., 0.2-0.3 mbar). 1H NMR (400 MHz, CDCl3) of first diastereomeric pair; δ 0.71 (d, J=7 Hz), 3H), 3.20-3.31 (m, 1H), 4.77 (d, J=10 Hz, 1H), 6.73 (br s, 1H), 7.23-7.42 (m, 5H), 8.55-8.60 (m, 2H). 1H NMR (400 MHz, CDCl3) of second diastereomeric pair: δ 1.24 (d, J=7 Hz), 3H), 2.90-3.11 (m, 1H), 4.22 (d, J=11 Hz, 1H), 6.71 (br s, 1H), 7.23-7.42 (m, 5H), 8.55-8.60 (m, 2H).

Quelle