Aza-Favorsky reaction with regioisomeric C- and N-linked 1,4-bis(imino)benzenes: Synthetic and reactivity dissimilarities

Structurally analogous C- and N-linked 1,4-bis(imino)-functionalized benzenes react with acetylenes in the KOBut/ DMSO superbase system to give the corresponding bis-(propargylamino)-containing derivatives in 62–82% yields (C-linking) or 38–42% yields (N-linking). In the latter case, with phenylacetylene, the yields of mono- and bisadducts were 32 and 38%, respectively. The observed dissimilarities between both bisimine chemotypes in the reactivity and synthetic outcomes imply the long-range adverse repulsive interaction between nitrogen anionic center and the second nitrogen atom in the N-linked 1,4-bis(imino) benzenes.