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Updated: Mar 10, 2026

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
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Formation of Seven-Membered Carbocycles via 7-endo Mode Cyclization of Lithioheptatrienes
Ken-Ichiro Kanno1, Eri Igarashi1, Yuki Mizukami1
1Institute for Catalysis and Graduate School of Life Science, Hokkaido University , Kita-ku, Sapporo 001-0021, Japan.
Abstract:
The highly selective synthesis of triene derivatives was achieved by a zirconocene-mediated three-component coupling reaction, and the trienes were efficiently subjected to 7-endo mode cyclization. The reaction of unsymmetrical zirconacyclopentadienes prepared from two different alkynes with N-bromosuccinimide (NBS) followed by treatment with allyl halides in the presence of CuCl afforded the corresponding heptatrienes in good yields. When the trienes reacted with an organolithium reagent, 7-endo mode cyclization occurred smoothly to give the corresponding cycloheptadiene.
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