Sequential Suzuki–Miyaura Cross-coupling Reactions of 4-Halopyrazolyl MIDA 3-Boronates: A Modular Synthetic Entry to 3,4-Bis(hetero)aromatic Pyrazoles

Abstract

Abstract The 1,3-dipolar cycloaddition of N-arylsydnones with ethynyl MIDA boronate produces mixtures of the corresponding regioisomeric pyrazolyl 3(4)-boronates, with the pyrazolyl 3-boronates predominating by a factor of 7:3. Further C-4 iodination of the latter opened access to 4-iodopyrazolyl MIDA 3-boronates as valuable scaffolds for the elaboration of unsymmetrically 1,3,4-trisubstituted pyrazole derivatives via Suzuki cross-coupling reactions.