Lithium Enables Pd-Catalyzed 5 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- carbocyclization, in contrast to the 6 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.

Access to 2-Alkenyl-furans via a Cascade of Pd-Catalyzed Cyclization/Coupling Followed by Oxidative Aromatization with DDQ.

An unprecedented DDQ-mediated oxidative aromatization of 2-bezylidene-dihydrofurans yielding 2-alkenyl-furans is disclosed. Integration of this transformation with a prior Pd-catalyzed reaction of α-propargylic-β-ketoesters and (hetero)aryl halides into a one-pot cascade process opens a direct modular route to highly substituted 2-vinyl-furans. Experimental and computational studies reveal that the crucial step of the oxidative-aromatization involves facile hydride transfer from the dihydrofuran ring to the O-center of DDQ.

Base-Catalyzed, Solvent-Free Synthesis of Rigid V-Shaped Epoxydibenzo[,][1,5]diazocines.

A novel method for the synthesis of epoxydibenzo[,][1,5]diazocines exhibiting a V-shaped molecular architecture is reported. The unique approach is based on unprecedented base-catalyzed, solvent-free autocondensation and cross-condensation of fluorinated -aminophenones. The structure of the newly synthesized diazocines was confirmed independently by X-ray analysis and chiroptical methods.