Annulation Producing Diverse Heterocycles Promoted by Cobalt Hydride

This study demonstrates the efficient synthesis of various heterocycles using the metal hydrogen atom transfer (MHAT)/ radical-polar crossover (RPC) method, emphasizing its versatility under mild conditions with high functional group tolerance. By distinguishing between cyclization and annulation, we underscore the complexity and efficiency of this approach in constructing intricate molecular architectures. Notably, the incorporation of an acetone solvent in the formation of cyclic acetal dioxanes from homoallylic alcohols reveals a novel annulation mechanism. Extensive substrate scope analysis and density functional theory calculations provide insights into reaction pathways, highlighting the critical role of cationic alkylcobalt(IV) intermediates and collidine in product selectivity. This study elucidates the mechanisms of the MHAT/RPC method and showcases its potential as a robust alternative to conventional synthetic strategies.