5-Aldehyde-2-thiophene borate ester was synthesized using 5-bromothiophene carboxaldehyde as a raw material, pinacol diboronate [B2(pin)2] as a boron reagent, and K3PO4·7H2O as a base, under the catalysis of chloro(2-dicyclohexylphosphino-2,4,6-triisopropyl-1,1-biphenyl)[2-(2-amino-1,1-biphenyl)]palladium(II) (Xphos-Pd-G2) and 2-dicyclohexylphosphino-2,4,6-triisopropylbiphenyl (Xphos). The target compound, 5-Formyl-2-thiopheneboronic acid, was then prepared by hydrolysis. The synthetic reaction formula for 5-Formyl-2-thiopheneboronic acid is shown in the figure below:
