Diversification of 4-Alkylpyridines: Mining for Reactivity with Alkylidene Dihydropyridines

Pyridines are valued structures in pharmaceutical development. Using a soft enolization approach, we can diversify alkyl pyridines under mild conditions via alkylidene dihydropyridines (ADHPs). Recent work in our group has demonstrated the utility of ADHPs in palladium-catalyzed reactions. However, the fundamental reactivity of ADHPs remains largely unexplored, with only scattered reports in the literature. We seek to further explore the reactivity of these electron-rich intermediates in different contexts, as new transformations can provide useful synthetic tools for pharmaceutical discovery. Herein we describe our investigations in this area, including the development of two new synthetic methods. Specifically, we describe the oxidation of ADHPs to the corresponding pyridylic ketones under mild conditions, and the iridium-catalyzed asymmetric alkylation of alkylidene dihydropyridines branch-allylated alkyl pyridines.