Nitrogen substituted cyclic enediynes: synthesis, thermal reactivity and complexation with metal ions

A number of N-substituted cyclic enediynes (azaenediynes) have been synthes ized via Pd(0)-catalysed ene-yne coupling followed by N-alkylation. The sim plest of them, a 10-membered monocyclic enediyne 1, underwent Bergman cycli zation (BC) at 23 degrees C with a half-life of 72 h. The kinetics of BC sl owed down considerably by fusing a benzene ring onto the enediyne. Several novel bis(azaenediyne)s and bis(diazaenediyne)s 3-6 have been synthesized. Their onset temperatures for BC were lowered under metal ion complexation c onditions.