Pyridine derivatives play a pivotal role in coordination chemistry and catalysis. A number of complexes involving coordination of different metals to a great variety of pyridine-containing ligands have been reported in the literature. In apparent contradiction with the easy formation of this sort of complex, transformations of the pyridine skeleton catalyzed by transition-metal complexes are very scarce and often suffer from harsh reaction conditions and/or limited substrate scope (for instance, pyridine itself proved to be particularly reluctant to partake in most of the reported catalytic processes).For these reasons, the ability to efficiently functionalize pyridines and their derivatives (e.g., quinoline, isoquinoline, etc.) remains an important issue in synthetic chemistry.

     On the other hand, the pyridine core is present in a huge number of relevant heteropolycycles. Among them, the indolizine framework is a common substructure in a number of biologically important natural products and pharmaceuticals and is used to provide a high level of fluorescence.4 Most synthetic strategies require starting from pyridinium N-methylides or pyridines with specific C2 functionalization.In contrast, only two annulation reactions of the pyridine ring that involve N-alkylation/nucleophilic cyclization have recently been reported.