Pd(II)/β-ICD-Cocatalyzed Asymmetric Route to Oxindole Scaffold via Cascade Reaction of Diazoacetamides and MBH-Carbonates

Recent advances in Pd-catalyzed asymmetric cyclization reactions

Over the past few decades, there have been major developments in transition metal-catalyzed asymmetric cyclization reactions, enabling the convenient access to a wide spectrum of structurally diverse chiral carbo- and hetero-cycles, common skeletons found in fine chemicals, natural products, pharmaceuticals, agrochemicals, and materials. In particular, a plethora of enantioselective cyclization reactions have been promoted by chiral palladium catalysts owing to their outstanding features. This review aims to collect the latest advancements in enantioselective palladium-catalyzed cyclization reactions over the past eleven years, and it is organized into thirteen sections depending on the different types of transformations involved.

Organocatalytic enantioselective allylic alkylation of α-aryl γ-lactones: an approach to densely functionalized quaternary stereocentres

The asymmetric allylic alkylation (AAA) of α-aryl γ-lactones involving the activation of Morita-Baylis-Hillman (MBH) carbonates by an original chiral Lewis base is reported. A wide range of γ-lactones bearing a quaternary stereocentre was thus obtained in both high yields and high enantiomeric ratios. The direct alkylation by MBH alcohol using in situ activation has been also established. Additionally synthetically useful functional transformations of groups surrounding the quaternary stereocentre have been performed.

Morita-Baylis-Hillman reaction of a chiral aziridine aldehyde

The Morita-Baylis-Hillman reaction of (R)-1-((R)-1-phenylethyl)aziridine-2-carbaldehyde with alkyl acrylate was carried out under various conditions by changing solvents, bases, and alcohol additives. The reaction at room temperature under neat conditions (no solvent) with quinuclidine as an amine nucleophile, in the presence of benzyl alcohol as an additive, afforded a product, γ-(aziridin-2-yl)-β-hydroxy-α-methylene butanoate, in 97% yield with a diastereomeric ratio of anti and syn as 86 : 14.

Enantioselective Michael Reaction of Cyclic β-Ketoesters with Morita-Baylis-Hillman Derivatives Using a Phase-Transfer Catalyst

This study aims to develop a highly enantioselective Michael reaction of cyclic β-ketoesters with Morita-Baylis-Hillman (MBH) derivatives using a phase-transfer catalyst. Cyclic β-ketoesters reacted with MBH derivatives to stereoselectively generate a quaternary carbon center in the presence of cinchona alkaloid-derived bulky ammonium catalyst, and aqueous KOH and Michael adducts bearing an acrylate moiety were obtained in good chemical yields with good enantioselectivity.

Trapping of Transient Zwitterionic Intermediates by N-Acylpyridinium Salts: A Palladium-Catalyzed Diastereoselective Three-Component Reaction

We developed a palladium-catalyzed diastereoselective three-component reaction of N-aryl diazoamides, pyridine, and chloroformate, which proceeded through trapping of transient zwitterionic intermediates by in situ formed N-acylpyridinium salts in a regioselective 1,4-addition fashion. This reaction can rapidly provide a library of biologically relevant 4-(2-oxoindolin-3-yl)-1,4-dihydropyridine derivatives in high yields (up to 98%) with moderate to excellent diastereoselectivities (up to >95:5 dr) under mild reaction conditions.

Synthesis of Functionalized 6-Hydroxy-2-oxindole Derivatives by Phenoxide Cyclization

An apparent intramolecular cross-dehydrogenative coupling of N-(3-hydroxy)monoanilide of maleic esters comprising base promoted phenoxide cyclization and subsequent base-mediated aerobic oxidation was developed to synthesize a variety of 2-(6-hydroxy-2-oxoindolin-3-ylidene)acetate derivatives. The isolation of intermediate cyclized products during the large scale reactions and their ready dehydrogenation with 1 equiv of base support this proposed two-step path.