[3 + 2 + 1] Pyridine Skeleton Synthesis Using Acetonitrile as C4N1 Units and Solvent.

The first [3 + 2 + 1] methodology for pyridine skeleton synthesis via cascade carbopalladation/cyclization of acetonitrile, arylboronic acids, and aldehydes was developed. This reaction proceeds via six step tandem reaction sequences involving the carbopalladation reaction of acetonitrile, a nucleophilic addition, a condensation, an intramolecular Michael addition, cyclization, and aromatization. Delightfully, both palladium acetate and supported palladium nanoparticles catalyzed this reaction with similar catalytic performance. The characterization results of the fresh and used supported palladium nanoparticle catalysts indicated that the reaction might be performed via a Pd(0)/Pd(II) catalytic cycle that began with Pd(0). Furthermore, the products showed good fluorescence characteristics. The green homogeneous/heterogenous catalytic methodologies pave a new way for constructing the pyridine skeleton.