An "on water" palladium-catalyzed direct (hetero)arylation of 2H-pyrazolo[3,4-b]pyridines has been developed. The reactions proceeds smoothly with at low catalytic loading at low temperature providing the C3 (hetero)arylated products in good to excellent isolated yields. Free NH 3-arylated 7-azaindazoles were also prepared by simple cleavage of the N-protected groups.

The stable radical cation of large aromatic hydrocarbons remains a challenge, due to the recessive aromatic character and high reactivity. Here we report the design, synthesis, and characterization of new aromatic π-radical cations from one π-electron oxidation of baytwisted dibenzoperopyrene derivatives. Experimental observations and theoretical calculations revealed that these π-radical cations had significant resonance hybrid structures, advantageous to the spin-and charge-delocalizations over the molecular backbones and emerging global aromaticity in the distorted π-system. Therefore, they are thermodynamically stable even without fully steric protection of all C−H bonds on the carbon skeleton and can be well characterized and studied routinely at ambient conditions. Moreover, the π-radical cation materials demonstrated readily formed magnetic molecule aggregates in the solution phase, while in powder states cationic monoradical characters were manifested and in the crystalline state intermolecular through-space interactions were popular. The phenomenon of varied magnetic activity in different states is experimentally investigated by various spectral means and X-ray crystallographic analysis, assisted by DFT calculations. Our study provides an insight into the resonance hybrid effects in the design of stable large aromatic hydrocarbon radical cations and demonstrates state-associated magnetic activities for π-radical cations, which are necessary in applications as magnetic materials.

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