Regioselective Late-Stage C-3 Functionalization of Pyrazolo[3,4-b]pyridines

This contribution reports for the first time the late-stage C–H activation of pyrazolo[3,4-b]pyridine derivatives. A family of 16 molecules functionalized on the C-3 position by this methodology is demonstrated. After a careful optimization, a reliable procedure has been developed with Pd(phen)2(PF6)2 catalyst (10 mol%), affording C-3 arylated pyrazolo[3,4-b]pyridines in yields ranging from 40 to 81%.