Lithium Enables Pd-Catalyzed 5-endo-dig Cyclization/Coupling of α‑Homopropargyl-β-ketoesters with Aryl Bromides and Triflates

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.

Polish National Science Centre (Grant 2016/22/E/ST5/00537); Wroclaw Centre for Networking and Supercomputing (https://wcss.pl), Grant 518.