Cesium carbonate → 4-(1-methyl-1H-pyrazol-5-yl)-2-thiophenecarboxylic Acid

Participants

Reaction Conditions

Reaction Steps

To a solution of 4-bromo-2-thiophenecarboxylic acid (3.91 g, 18.9 mmol) in dioxane/H2O (4:1, 100 mL) was added Cs2CO3 (21.7 g, 66.6 mmol), tetrakistriphenylphosphine Pd(0) (1.1 g, 0.95 mmol) and 1-methyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (3.94 g, 18.94 mmol) [prepared according to the procedure of Preparation 7]. The reaction mixture was heated to 85° C. in a sealed tube for 12 hours and partitioned between H2O and CHCl3. The pH of the aqueous phase was adjusted to ˜3 with 6N HCl and washed several times with CHCl3. The combined organic fractions were dried (Na2SO4), concentrated under vacuum and used directly without further purification (2.84 g, 13.64 mmol, 72%): LC-MS (ES) m/z=209 (M+H)+.

Provenance & Evidence