Palladium‐Catalyzed Cascade Annulation To Construct Functionalized β‐ and γ‐Lactones in Ionic Liquids

Abstract

A highly efficient and mild palladium-catalyzed, one-pot, four-step cascade annulation has been developed to afford functionalized b-and g-lactones in moderate to good yields with high regio-and diastereoselectivities in ionic liquids. The employment of ionic liquids under mild reaction conditions makes this transformation green and practical. Especially, this reaction provided a novel and convenient methodology for the construction of naturally occurring biologically active b-and g-lactones. Scheme 4. Cascade annulation of alkynoates with 5 in [C 2 OHmim]Cl. Reaction conditions: 7 (0.25 mmol), 5 (0.30 mmol), PdCl 2 (3 mol %), AgNO 3 (0.5 mmol), [C 2 OHmim]Cl (0.5 mL), and CH 3 CN (0.1 mL) at room temperature. Scheme 5. Synthetic transformations of 8 b. Scheme 6. Plausible reaction mechanism. Angewandte Chemie 7349

Nickel‐Catalyzed 1,2‐Diarylation of Alkenyl Carboxylates: A Gateway to 1,2,3‐Trifunctionalized Building Blocks

“…[7] We reasoned that the utility of this chemistry could be enhanced if other functional groups commonly encountered in synthesis could serve as directing groups. [8] Given the versatility of carboxylic acids as diversifiable starting materials and their abundance as chemical feedstocks, [9,10] we envisioned that the development of ac arboxylate-directed [11] 1,2-diarylation of alkenes would be synthetically enabling.H ence,t he goal of the present study was to demonstrate the feasibility of using free alkenyl carboxylic acid starting materials in nickel-catalyzed conjunctive cross-coupling (Scheme 1C).…”