Substrate-Controlled Regio- and Stereoselective Synthesis of ( Z)- and ( E)- N-Styrylated Carbazoles, Aza-carbazoles, and γ-Carbolines via Hydroamination of Alkynes.

We report herein the substrate-controlled regio- and stereoselective hydroamination of carbazoles, aza-carbazoles, and γ-carbolines with functionalized aromatic as well as aliphatic alkynes in a KOH/DMSO system in good yields. The electronic effect of the substrates governs the stereochemistry of the product. Electron-donating alkynes provided ( Z)-stereoselective products, and electron-withdrawing alkynes provided ( E)-stereoselective products. This approach also provides an easy route for the synthesis of mono- and bis-hydroaminated product. The deuterium-labeling studies were also conducted to support the mechanistic pathway.