Sulfuric Acid → Tert-butyl 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxylate

Participants

Reaction Conditions

Reaction Steps

A solution of 5 g of 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxylic acid in 35 ml of dioxane is introduced into a 250 ml autoclave and then cooled to -10° C. 2 ml of concentrated H2SO4 and 70 ml of 2-methylpropene, cooled to -10° C., are then added and the autoclave is closed, allowed to warm up to RT and then heated at 40° C. for 18 hours, with vigorous stirring. After cooling to RT, the reaction mixture is concentrated under vacuum, the residue is extracted with DCM, the organic phase is washed with water, with 5% Na2CO3 solution and with saturated NaCl solution and dried over MgSO4 and the solvent is evaporated off under vacuum. The residue is chromatographed on silica using a toluene/AcOEt mixture (from 90/10 to 80/20; v/v) as the eluent to give 3.15 g of the expected product, m.p.=112° C.

Provenance & Evidence