Chiral Bis‐Oxalamide‐Rare Earth Complex Catalyzed Inverse‐ Electron‐Demand Asymmetric oxa‐Hetero‐Diels‐Alder Reaction for Optically Active Dihydropyran Core Structures

Abstract

Chiral bis-oxalamide (CBOA)/rare-earth metal complexes-catalyzed asymmetric inverse-electrondemand oxa-hetero-Diels-Alder (HDA) reactions were investigated under mild reaction conditions, which was performed between β,γ-unsaturated α-ketoesters and various electron-riched dienophiles, such as cyclopentadiene, 2,3-dihydrofuran, 3,4-dihydro-2H-pyran, tetrahydropyridine as well as phenyl(vinyl)sulfane. Several series of optically active functionalized 3,4-dihydro-2H-pyran or ring fused dihydropyran derivatives were obtained in high yields with high diastereo-and enantioselectivity. The procedure was able to tolerate a relatively wide range of substrates. The coordination mode of chiral bis-oxalamide with Sc(III) was demonstrated by the X-ray crystallographic structure, and DFT calculations were carried out to uncover the regio-and stereocontrol.

Sulfur in Waste‐Free Sustainable Synthesis: Advancing Carbon–Carbon Coupling Techniques

“…The use of vinyl sulfides as dienophiles for Diels-Alder reactions (both in full carbon and heteroatomic versions) is conventional and does not require special discussion. As a demonstration of the great importance of vinyl sulfides in this field, there are several recent examples of enantioselective syntheses, [75][76][77][78] the assembly of complex natural scaffolds, [79] and photochemically induced reactions. [80] A similar situation is observed in the case of [2 + 3] dipolar cycloaddition [81][82][83] and [2+2] cycloaddition.…”

Recent Developments in Enantioselective Scandium-Catalyzed Transformations

“…Chiral dihydropyran derivatives are privileged and prevalent structures in many natural and bioactive products. In 2022, Wang, Qi and Wang developed enantioselective scandium-catalyzed inverse-electron-demand oxa-Diels-Alder reactions between β,γ-unsaturated α-ketoesters 119 and various types of electron-enriched dienophiles, such as cyclopentadiene, 2,3-dihydrofuran, 3,4-dihydro-2H-pyran, and tetrahydropyridine (Scheme 30) [73]. To promote these reactions, the authors selected a previously designed chiral bis-oxalamide ligand 120 to be combined at 12 mol% of a catalyst, loading to 10 mol% of Sc(OTf) 3 as a precatalyst.…”

“…Scheme 30. Oxa-Diels-Alder reactions of β, γ-unsaturated α-ketoesters with cyclopentadiene/2,3dihydrofuran/3,4-dihydro-2H-pyran/tetrahydropyridine [73].…”

A Class of Enantiomerically Pure Bis-oxamide Palladium Complexes: Modular Synthesis via Domino C(sp2)–H Bond Arylation and Photophysical Property

“…In 2015, Que developed a protocol for γ-diarylation of benzyl amines by using oxalyl amide as the directing group to prepare N -acyl-2,6-diarylbenzylamine derivatives . In recent years, our group reported efficient copper- or rare earth metal-catalyzed asymmetric inverse-electron demand oxo-hetero-Diels–Alder (HDA) reactions with chiral bis-oxamide (CBOA) ligands (Scheme c) . Although this type of chiral oxamide ligand for Pd­(II) was mostly initiated from related amide ligand MPAA, pioneeringly reported by Yu’s group, the structural data for the metal–oxamide species are still scarce, and even elusive in some cases, presumably owing to the inherently labile nature of the oxamide–metal complexes.…”