Reaktion #40777

Reaktionsgleichung

hydrazine hydrate

2-benzylidene-butyraldehyde

H2O

→

desired product

Ausbeute 94.0%

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

Ausbeute 94.0%

Lösungsmittel

diethylether

ether

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.STIRRINGThe mixture was stirred overnight (with ice bath)
2. 2
   workup.ADDITIONwas added
3. 3
   Sonstigethe organic layer was separated
4. 4
   Extraktionthe aqueous layer was extracted 2 times with diethylether
5. 5
   TrocknenThe combined organic layers were dried over Na2SO4
6. 6
   Filtrationfiltrated
7. 7
   Einengenconcentrated in vacuo
8. 8
   SonstigeVacuum destination yielded 6.1 g of a clear fluid (102-106° C., 0.6 mbar)

Vorschrift

62 ml (10 equiv.) hydrazine hydrate was added to 150 mL diethylether. The emulsion was cooled with an ice/NaCl bath to −10° C. A solution of 20.4 g 2-benzylidene-butyraldehyde in 100 mL ether was added dropwise at −10° C. and stirred at −10° C. for 3 hours. The mixture was stirred overnight (with ice bath) and allowed to slowly reach room temperature H2O was added, the organic layer was separated and the aqueous layer was extracted 2 times with diethylether. The combined organic layers were dried over Na2SO4, filtrated and concentrated in vacuo. Vacuum destination yielded 6.1 g of a clear fluid (102-106° C., 0.6 mbar) containing 94% of the desired product (mixture of diastereomeric pairs). Characteristic signals of the first diastereomeric pair: 1H NMR (400 MHz, CDCl3) δ 0.83 (t, J=6.5 Hz, 3H), 3.03-3.13 (m, 1H), 4.74-4.81 (m, 1H), 6.83 (br s, 1H). Characteristic signals of the second diastereomeric pair: 1H NMR (400 MHz, CDCl3) δ 1.00 (t, J=7.5 Hz, 3H), 2.84-2.93 (m, 1H), 4.28-4.34 (m, 1H), 6.76 (br s, 1H).

Quelle