Transition Metal-Mediated Intramolecular [2+2+2] Cycloisomerizations of Cyclic Triynes and Enediynes

Nitrogen-containing 15-membered triacetylenic macrocycles known as 1,6,11-tris(arylsulfonyl)-1,6,11-triazacyclopentadeca-3,8,13-triynes (1) and enediynic macrocycles called 1,6,11-tris(arylsulfonyl)-1,6,11-triazacyclopentadeca-3-ene-8,13-diynes (4 and 5) were satisfactorily prepared. [2+2+2] cycloisomerization processes catalyzed by transition metals were tested in the above-mentioned macrocycles. Readily available and familiar cyclotrimerization precatalysts were examined for efficiency. Among them, the RhCl(CO)(PPh₃)₂ complex was found to catalyze the cycloisomerization reaction giving the desired cycloadducts in high yields.