Palladium‐Catalyzed Enantioselective [4+2] Cycloaddition of 4‐Vinylbenzodioxinones with Barbiturate‐Derived Alkenes: Con‐struction of Chiral Spirobarbiturate−Chromanes

Abstract

In this paper, Pd‐catalyzed [4 + 2] decarboxylative cycloaddition of 4‐vinylbenzodioxinones with barbiturate‐derived alkenes has been developed, leading to various spirobarbiturate‐chromane derivatives in high yields with excellent diastereo‐ and enantioselectivities. The scale‐up reaction and further derivation of the product were demonstrated. A plausible reaction mechanism was also proposed.

Palladium-Catalyzed Cycloaddition Reactions of π–Allylpalladium 1,4-Dipoles with 1,3,5-Triazinanes: Access to Hexahydropyrimidines, 1,3-Oxazinanes, and 1,5-Diazocanes

“…In 2021, a palladium/Lewis acid-catalyzed decarboxylative [5 + 2] annulation of 4-methylene-5-vinyl-1,3-dioxolan-2-ones with 1,3,5-triazinanes toward the synthesis of nonfused N -aryl azepane derivatives was discovered by Guo and co-workers (Scheme c) . Despite the successful construction of heterocyclic compounds through the cyclization reaction of 1,3,5-triazinanes with π-allylpalladium 1,3-dipoles , and the wide application of π-allylpalladium 1,4-dipoles in the efficient synthesis of heterocyclic compounds through cyclization reactions, the [4 + 2] cycloaddition reaction of π-allylpalladium 1,4-dipole precursors with 1,3,5-triazinane has not yet been achieved. To the best of our knowledge, the 5-methylene-1,3-oxazinan-2-ones could be used for the generation of aza-π-allylpalladium 1,4-dipole species, thereby undergoing allylic alkylation with diverse nucleophiles and further cyclization for the construction of nitrogen-containing heterocycles. , Inspired by these pioneering reports, and in continuation of our ongoing research interest in palladium-catalyzed decarboxylation for in situ formation of π-allylpalladium dipole intermediates and used in various cyclization, recently, we have developed a palladium-catalyzed decarboxylation of 5-methylene-1,3-oxazinan-2-ones to generate highly active aza-π-allylpalladium 1,4-dipoles, which could react with 1,3,5-triazinanes via [4 + 2] cycloaddition to access hexahydropyrimidines and undergo dimeric [4 + 4] cycloaddition for the construction of 1,5-diazocanes (Scheme , bottom).…”

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

“…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) . As our continuous efforts on cycloaddition reactions, in order to further expand the application scope of 4-vinylbenzodioxinones, we herein report a palladium-catalyzed (4 + 1) cycloaddition of sulfur ylides with 4-vinylbenzodioxinones, producing various dihydrobenzofuran derivatives (Scheme b).…”