Methylation of imidazopyrazine, imidazoquinoxaline, and pyrazoloquinoxaline through Suzuki–Miyaura cross coupling

The Suzuki–Miyaura cross coupling is a versatile and powerful reaction for carbon–carbon bond formation which nevertheless requires optimization of conditions. While the coupling of arylboron derivatives with aryl or alkenyl halides has been widely explored, alkylation has attracted less attention. We describe herein the methylation of bromo derivatives of imidazopyrazine, imidazoquinoxaline, and pyrazoloquinoxaline having biologically interesting structures. As the challenging Suzuki–Miyaura reaction is highly substratedependent, the choices of the base, solvent, and additive are also discussed.