[reaction: see text] Triynes 1 could effectively be cyclotrimerized to annulated benzenes 2 by treatment with a catalytic amount of zinc powder, N-heterocyclic carbene, and CoCl(2) or FeCl(3).

An iron species derived from FeCl 2 or FeCl 3 by in situ reduction with zinc powder in the presence of imidazol-2-ylidene or bidentate nitrogen ligand could effectively catalyze intramolecular cycloisomerization of triynes to annulated benzenes. With a 2-iminomethylpyridine ligand, hydrates of FeCl 2 and FeCl 3 as well as their anhydrous ones could be used.

An iron species derived from FeCl 2 or FeCl 3 by in situ reduction with zinc powder in the presence of imidazol-2-ylidene or bidentate nitrogen ligand could effectively catalyze intramolecular cycloisomerization of triynes to annulated benzenes. With a 2-iminomethylpyridine ligand, hydrates of FeCl 2 and FeCl 3 as well as their anhydrous ones could be used.

Zn or -FeCl3/Zn. -A novel title reaction is demonstrated for a variety of substituted triynes affording tricycles in good yields. The reaction is also extended to the formation of heterocycles (IV) and (VI). Double cyclotrimerization affords the product (VIII) in quantitative yield. -(SAINO, N.; KOGURE, D.; OKAMOTO*, S.; Org. Lett. 7 (2005) 14, 3065-3067; Dep. Appl. Chem., Fac. Eng., Kanagawa Univ., Kanagawa, Yokohama 221, Japan; Eng.) -R. Steudel 45-135