Four-membered Rings with Two Nitrogen Atoms

Synthesis and Functionalization of 3-Alkylidene-1,2-diazetidines Using Transition Metal Catalysis

“…Indeed, they have been studied computationally as components of β-turn mimetics . Unfortunately, systematic exploration of the practical applications of 1,2-diazetidines in medicinal chemistry has been severely hampered by a lack of high-yielding, general routes for their preparation and functionalization . The best synthetic methods developed to date involve the following: [2π + 2π] cycloadditions of azodicarbonyl compounds with electron-rich alkenes, “on water” [2σ + 2σ + 2π] cycloadditions of azodicarboxylates with quadricyclane, Pd-catalyzed ring closure of 2,3-allenyl hydrazines, bisalkylation of 1,2-dialkylhydrazines with 1,2-dibromoethane, and Hard−Soft Acids and Bases (HSAB) controlled ring closure .…”