Potassium Carbonate → Methyl 5-chloro-4-(1-methyl-1H-pyrazol-5-yl)thiophene-2-carboxylate

Participants

Reaction Steps

A solution of methyl 4-bromo-5-chloro-2-thiophenecarboxylate (5 g, 19.57 mmol)[prepared in Preparation 2], 1-methyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (4.28 g, 20.55 mmol)[prepared in Preparation 1], potassium carbonate (10.82 g, 78 mmol) and bis(tri-t-butylphosphine)palladium(0) (0.500 g, 0.978 mmol) in 1,4-dioxane (82 ml) and water (16.31 ml) was stirred at 80° C. in a sealed tube for 2 h. The reaction mixture was partitioned between H2O-DCM and the aqueous phase was washed several times with DCM. The combined organic fractions were dried over Na2SO4, concentrated and purified via column chromatography (silica, 25% EtOAc in hexanes) yielding methyl 5-chloro-4-(1-methyl-1H-pyrazol-5-yl)-2-thiophenecarboxylate (3.2 g, 12.47 mmol, 63.7% yield) as a white solid: LCMS m/e ES 257, 259 (M, M+2)+.

Provenance & Evidence