The unique reactivity of 5,6-unsubstituted 1,4-dihydropyridine in the Huisgen 1,4-diploar cycloaddition and formal [2 + 2] cycloaddition

Abstract

The three-component reaction of isoquinolines, dialkyl acetylenedicarboxylates, and 5,6-unsubstituted 1,4-dihydropyridines in acetonitrile at room temperature afforded functionalized isoquinolino[1,2-f][1,6]naphthyridines in good yields and with high diastereoselectivity. More importantly, the formal [2 + 2] cycloaddition reaction of dialkyl acetylenedicarboxylates and 5,6-unsubstituted 1,4-dihydropyridines in refluxing acetonitrile gave unique 2-azabicyclo[4.2.0]octa-3,7-dienes as major products and 1,3a,4,6a-tetrahydrocyclopenta[b]pyrroles as minor products via further rearrangement.

Rapid construction of tricyclic tetrahydrocyclopenta[4,5]pyrrolo[2,3-b]pyridine via isocyanide-based multicomponent reaction

“…In recent years, 5,6-unsubstituted 1,4-dihydropyridines have been recognized as the reactive electron-rich dienophiles, which proceeded several Povarov reactions with various 1-aza-1,3-butadienes [ 40 – 44 ]. Recently, we have found that the three-component reaction of isoquinolines, dialkyl but-2-ynediaotes and 5,6-unsubstituted 1,4-dihydropyridines afforded functionalized isoquinolino[1,2- f ][1,6]naphthyridines in good yields and with high diastereoselectivity via a [4 + 2] cycloaddition process [ 45 ]. Very recently, we also found that base-promoted [4 + 2] cycloaddition of salicyl N -tosylimines and 5,6-unsubstituted 1,4-dihydropyridines resulted in novel tetrahydrochromeno[3,2- b ]pyridine derivatives in satisfactory yields [ 46 ].…”