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Updated: Jun 12, 2025

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
Published on: March 20, 2017
Lithium Enables Pd-Catalyzed 5-endo-dig Cyclization/Coupling of α-Homopropargyl-β-ketoesters with Aryl Bromides and
Bartosz Bisek1, Katarzyna Kochaniak1, Wojciech Chaładaj1
1Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
Abstract:
Tight chelation of enolate by lithium alters the selectivity of tandem palladium-catalyzed cyclization/coupling of terminal α-homopropargyl-β-ketoesters with aryl halides. In the presence of LiOH, substituted cyclopentenes are preferentially formed via 5-endo-dig carbocyclization, in contrast to the 6-exo-dig oxocyclization exclusively observed in the absence of a hard, chelating metal center. The disclosed transformation, featuring mild conditions and broad functional group tolerance, can be applied for a variety of (hetero)aryl bromides as well as aryl and vinyl triflates.
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