Organocalcium Hydride-Catalyzed Intramolecular C(sp³)–H Annulation of Functionalized 2,6-Lutidines

Abstract

This work reports an intramolecular C(sp3)–H annulation of functionalized 2,6-lutidines catalyzed by an organocalcium hydride [{(DIPPnacnac)CaH(thf)}2] (DIPPnacnac = CH{(CMe)(2,6- i Pr2–C6H3N)}2). This reaction constitutes a streamlined approach for producing a new family of tetrahydro-1,5-naphthyridines and hexahydropyrido[3,2-b]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.

1,2-trans-Diaminocyclohexane (DACH) in Asymmetric Catalysis: Nearing Fifty Years of Faithful Service and Counting

“…16 for the aza-Michael/Mannich cascade reaction of -imino-oxobutanamides 685, formed in situ from N-alkoxyacetoacetamide 683 and nitrosobenzene 684, with methyleneindolinones 686 to afford spiro-oxindole-3,3′--lactams 687 with three contiguous stereocenters (two quaternary) in moderate to good yields and with diastereoselectivities up to 10:1 and enantioselectivities >99% ee (Scheme 233). 785 Wang 786 described the first efficient and enantioselective Friedel-Crafts alkylation/cyclization cascade of naphthols 688 with a variety of ,-unsaturated -keto esters 689 catalyzed by rosin-derived DACH thiourea Cat. 82 to afford various potentially bioactive and optically active functionalized chromanes 690 in high yields and high enantioand diastereoselectivities (Scheme 234a).…”