反应详情

Cesium carbonate (35.2 g, 108 mmol), 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (0.4 g, 0.7 mmol) and tris(dibenzylideneacetone)dipalladium(0) (0.2 g, 0.2 mmol) were added to a solution of ethyl 5-amino-1-methylpyrazole-4-carboxylate (15.3 g, 90 mmol) in dioxan (50 ml) under an inert atmosphere. A solution of 3-bromo-2-nitrotoluene (16.2 g, 75 mmol) in dioxane (10 ml) was added and the mixture was stirred for 30 min at room temperature then heated at reflux for 72 h. The suspension was filtered through Celite® filter agent, washed with EtOAc and the filtrate was concentrated in vacuo. The residue was purified by flash chromatography on silica gel (eluant; 50% EtOAc:50% pet. ether) then recrystallised from EtOAc/pet. ether to yield the title compound (12.5 g, 45%).

1. temperaturethen heated
2. temperatureat reflux for 72 h
3. filtrationThe suspension was filtered through Celite®
4. filtrationfilter agent
5. washwashed with EtOAc
6. concentrationthe filtrate was concentrated in vacuo
7. customThe residue was purified by flash chromatography on silica gel (eluant; 50% EtOAc:50% pet. ether)
8. customthen recrystallised from EtOAc/pet. ether