Organocalcium Hydride-Catalyzed Intramolecular C(sp)-H Annulation of Functionalized 2,6-Lutidines.

This work reports an intramolecular C(sp)-H annulation of functionalized 2,6-lutidines catalyzed by an organocalcium hydride [{(nacnac)CaH(thf)}] (nacnac = CH{(CMe)(2,6-Pr-CHN)}). This reaction constitutes a streamlined approach for producing a new family of tetrahydro-1,5-naphthyridines and hexahydropyrido[3,2-]azocines derivatives in good to excellent yields with high atom efficiency and broad substrates scope. A calcium alkyl complex was isolated from the stoichiometric reaction between calcium hydride and the substrate through deprotonation, which was structurally characterized and confirmed as the catalytic intermediate.