Inverse-Electron-Demand Aza-[4+2] Cycloadditions Between 1,3-Aazadiene And In Situ Generated Metallo-Ynamides

The 1,4-dihydropyridine skeleton is among the most important heterocyclic pharmacophores and has been found as the structural core in many clinical pharmaceuticals; meanwhile it also serves as versatile building blocks in organic synthesis. Based on our recent studies on the formation of ynamido-metal intermediates, a Cs₂CO₃-promoted aza-[4+2] cycloaddition reaction between in situ generated ynamido-metal species and 1,3-azadiene have been reported, giving access to a variety of 1,4-dihydropyridines under mild conditions. The obtained 1,4-dihydropyridine products could be converted into substituted pyridines upon treatment with NaOH via desulfonation and aromatization cascades. Moreover, several metal-mediated cyclization reactions of these present products have also been investigated to give a set of 7-azaindoles.