Palladium-Catalyzed [5 + 4] Cycloaddition of 4-Vinyl-4-Butyrolactones with N-Tosyl Azadienes: Construction of Nine-Membered Ring

Abstract

In this paper, we reported the palladium-catalyzed formal [5 + 4] cycloaddition reactions between 4-vinyl-4-butyrolactones (VBLs) and azadienes. Under mild reaction conditions, a wide range of benzofuran-fused 9-membered heterocyclic compounds had been provided in moderate to excellent yields with exclusive regioselectivities and excellent diastereoselectivities. The practical applicability of the synthesis was demonstrated through scale-up reaction and further transformation.

Palladium-Catalyzed (4 + 1) Annulation of 4-Vinylbenzodioxinones with Sulfur Ylides: Diastereoselective Synthesis of Dihydrobenzofuran Derivatives

“…In the past decades, the palladium-catalyzed cycloaddition reaction has become one of the most powerful and efficient methods to construct carbo- and heterocyclic frameworks . Various cycloaddition reactions via allylpalladium intermediates have been developed for the synthesis of cyclic compounds. − Numerous dipolarophiles, such as electron-deficient alkenes, imines, aldehydes, and 1,3-diploes, have been applied in palladium-catalyzed cycloaddition reactions. As a type of readily accessible compound, sulfur ylides have also been successfully used in Pd-catalyzed cycloaddition reactions because of their intrinsic nucleophilic and electrophilic properties.…”

“…In this context, we conceived of constructing oxy-heterocycles with the use of sulfur ylides in Pd-catalyzed cycloaddition reactions. We have been dedicated to designing and synthesizing novel π-allylpalladium precursors with unique skeletons for achieving new Pd-catalyzed cycloaddition reactions in recent years. , Most recently, considering the high value of benzo-oxy heterocycles, we designed and synthesized 4-vinylbenzodioxinones as a novel precursor of π-allylpalladium zwitterionic intermediate and applied them in palladium-catalyzed (4 + 3) decarboxylation cycloaddition with C, N-cyclic azomethine imines, leading to various biologically important 1,3,4-benzoxadiazepine derivatives in satisfactory yields with good stereoselectivities (Scheme a) . We also developed a Pd-catalyzed (4 + 2) cycloaddition of 4-vinylbenzodioxinones with barbiturate-derived alkenes, affording various spirobarbiturate-chromane derivatives in high yields with excellent diastereo- and enantioselectivities (Scheme a) .…”