Diastereoselective Construction of Tetrahydropyridine Fused Bicyclic Structures via Three-Component Domino Reaction

The three-component reactions of
enals, electron-deficient alkynes,
and hydroxyl-functionalized primary amines for the highly diastereoselective
construction of dihydro-3H-benzo­[4,5]­oxazolo­[3,2-a]­pyridines, hexahydropyrido­[2,1-b]­[1,3]­oxazines,
and tetrahydro-2H-oxazolo­[3,2-a]­pyridines
have been achieved. Domino formation of one C–C, two C–N,
and one C–O bonds are furnished in these reactions. This bis-annulation
protocol allows for the synthesis of fused heterocyclic products of
high structural diversity with variation not only of appended fragments
but also the ring size of the central backbone.