Synthesis of diverse di- to penta-substituted 1,2-dihydropyridine derivatives from gold(I)-catalyzed intramolecular addition of tertiary enamides to alkynes

As 3-aza-1,5-enynes, internal and terminal alkyne-bearing tertiary enamides underwent an efficient Au(I)-catalyzed 6-endo-dig cyclization reaction to afford a variety of di- to penta-substituted 1,2-dihydropyridine derivatives in high yields. The cyclization proceeds through a cascade comprising an intramolecular nucleophilic addition of enaminic carbon to alkyne–gold(I) complex, deprotonation, and protodeauration steps. Au(I)-catalyzed tertiary enamide–alkyne cyclization coupled with consecutive oxidative aromatization provided a straightforward route to polysubstituted pyridines.