Réaction #48034

Équation de réaction

ethyl 2-chloro[(4-chlorophenyl) hydrazono]acetate

styrene

triethylamine

→

ethyl 1-(4-chlorophenyl)-5-phenyl-4,5-dihydro-(1H)-pyrazole-3-carboxylate

Rendement 94.0%

Solvants

benzene

Conditions de réaction

Traitement

1. 1
   Températurethe resulting solution is heated
2. 2
   Températureat reflux temperature for 1 hour
3. 3
   Autrethe formed precipitate is removed by filtration
4. 4
   Lavagewashed with toluene
5. 5
   ConcentrationThe filtrate is concentrated in vacuo
6. 6
   Autrepurified by flash chromatography (silica gel, dichloromethane)

Mode opératoire

Part B: To a stirred boiling solution of ethyl 2-chloro[(4-chlorophenyl) hydrazono]acetate (22.95 gram, 0.088 mol) and styrene (30.3 ml, 0.264 mol) in benzene (140 ml) is added triethylamine (34.3 ml, 0.247 mol) and the resulting solution is heated at reflux temperature for 1 hour. The resulting solution is cooled to room temperature and the formed precipitate is removed by filtration and washed with toluene. The filtrate is concentrated in vacuo and purified by flash chromatography (silica gel, dichloromethane) to give ethyl 1-(4-chlorophenyl)-5-phenyl-4,5-dihydro-(1H)-pyrazole-3-carboxylate (27.2 gram, 94% yield) as a syrup which slowly solidifies on standing. 1H-NMR (200 MHz, CDCl3): 1.38 (t, J=7 Hz, 3H), 3.06 (dd, J=18 and 7 Hz, 1H), 3.73 (dd, J=18 and 13 Hz, 1H), 4.33 (q, J=7 Hz, 2H), 5.38 (dd, J=13 and 7 Hz, 1H), 7.02 (br d, J=8 Hz, 2H), 7.08-7.40 (m, 7H).

Source