Catalyst- and Base-Controlled Site-Selective sp2 and sp3 Direct Arylation of 5,7-Dimethyl-2-phenylpyrazolo[1,5-a]pyrimidine Using Aryl Bromides.

The palladium-catalyzed direct C–H arylation of various heterocyclic is now recognized to be the most effective methodology for making aromatic compounds. In this paper, we present a new approach to control the site-selective direct C–H arylation of both sp2 and sp3 sites in 5,7-dimethyl-2-phenylpyrazolo[1,5-a]pyrimidine by using aryl bromides. The desired compounds were obtained in satisfactory yields. The effects of each reaction parameter including catalyst, base, and solvent were investigated.