Diastereodivergent Catalytic Asymmetric Michael Addition of 2-Oxindoles to α,β-Unsaturated Ketones by Chiral Diamine Catalysts

Diastereodivergence in catalytic asymmetric conjugate addition of carbon nucleophiles

Catalytic asymmetric conjugate additions of carbon nucleophiles have emerged as a potent tool for constructing multi-stereogenic molecules with precise stereochemical control. This review explores the concept of diastereodivergence in such reactions, focusing on strategies to achieve selective access to diverse diastereomeric products upon carbon-carbon bond formation. Drawing from a rich array of examples, we delve into key approaches for controlling the stereochemical outcome of these transformations, including alteration of alkene geometry, fine-tuning of reaction parameters, synergistic catalysis, and isomerization of conjugate adducts. Additionally, we highlight the iterative strategies for conjugate additions, showcasing their potential for diastereodivergent synthesis of methyl-branched stereocenters in 1,3-relationships. By presenting a concentrated overview of this significant topic, this review aims to provide valuable insights into the design and execution of stereodivergent catalytic conjugate additions, offering new avenues for advancing stereoselective synthesis and structural diversity in organic synthesis.

Modular synthesis of 3,3-disubstituted oxindoles from nitrones and acrylic acids

We developed a modular synthesis for 3,3-disubstituted oxindoles, utilising readily accessible nitrones and acrylic acids. This approach facilitates the preparation of a diverse array of oxindoles through the variation of the starting materials. We demonstrated the applicability of this method through a gram-scale reaction and a synthesis of esermethole.

Asymmetric Synthesis of Arboduridine

The first asymmetric total synthesis of the monoterpenoid indole alkaloid arboduridine has been accomplished. The tricyclic A/B/D ring system was constructed by an enantioselective Michael reaction followed by intramolecular nucleophilic addition. Intramolecular α-amination of a ketone forged the piperidine ring, while a Horner-Wadsworth-Emmons (HWE) reaction was used to form the pyrrolidine ring. A reduction cyclization cascade led to formation of the tetrahydrofuran ring.

Water enables diastereodivergency in bispidine-based chiral amine-catalyzed asymmetric Mannich reaction of cyclic N-sulfonyl ketimines with ketones

Tuning diastereoselectivity is a great challenge in asymmetric catalysis for the inherent stereochemical bias of the substrates. Here, we report a diastereodivergent asymmetric Mannich reaction of cyclic N-sulfonyl ketimines with ketones catalyzed by a bispidine-based chiral amine catalyst, in which additional water switches the diastereoselectivity efficiently. Both chiral anti- and syn-benzosultams with potential anti-HIV-1 activity are obtained in excellent yields and good to excellent ee values. Control experiments and density functional theory (DFT) calculations were applied to study the diastereodivergent mechanism, which reveal that the diastereodivergent catalysis should be state-determined, and the water reverses the energies of states to realize the diastereodivergency. The findings are quite new and might inspire more diastereodivergent asymmetric synthesis.

A diastereodivergent asymmetric Mannich reaction of cyclic N-sulfonyl ketimines with ketones is realized by employing bispidine-based chiral amine as catalyst and additional water switching the diastereoselectivity.

Primary amine catalyzed diastereo- and enantioselective Michael reaction of thiazolones and α,β-unsaturated ketones

The chiral primary amine catalyzed asymmetric Michael reaction of thiazolones and α,β-unsaturated ketones was reported. Two different optimal catalytic systems were obtained corresponding to cyclic and linear α,β-unsaturated ketones. By employing chiral primary amines as the catalysts and amino-acid derivatives as the additives, a variety of Michael adducts containing the scaffold of the thiazole ring were prepared in moderate to good yields and with excellent diastereo- and enantioselectivities (up to 95% yield, all up to >19/1 dr, up to 96% ee). The reaction was scaled up to obtain 1.73 grams of the Michael adduct with the maintenance of yield and stereoselectivity.

Asymmetric synthesis of highly functionalized furanones via direct Michael reactions mediated by a bulky primary amine

A bulky chiral primary amine catalyzed Michael reaction of 3(2H)-furanones has been realized, leading to the construction of substituted furanone derivatives.

Organocatalytic asymmetric Michael addition between 3-subsituted oxindoles and enals catalyzed by camphor sulfonyl hydrazine

3,3-Disubstituted oxindoles containing vicinal stereogenic carbon centers have been synthesized through organocatalytic asymmetric Michael addition between 3-substituted oxindoles and enals catalyzed by chiral camphor sulfonyl hydrazines (CaSHs).

Enantioselective Michael addition of malonates to α,β-unsaturated ketones catalyzed by 1,2-diphenylethanediamine

A general and highly enantioselective Michael addition of malonates to cinnamones and chalcones has been developed. The commercially available 1,2-diphenylethanediamine could be directly utilized as the organocatalyst to furnish the desired adducts in satisfactory yield (61–99%) and moderate to excellent enantiopurity (65 to >99% ee). β-Ketoester was also a competent donor and was employed to construct densely functionalized cyclohexenones via a tandem Michael-aldol condensation process.

1,2-Diphenylethanediamine could be directly utilized to promote the Michael addition of malonates and β-ketoesters to various α,β-unsaturated ketones.

Stereodivergent Catalysis

This review covers diastereo- and enantiodivergent catalyzed reactions in acyclic and cyclic systems using metal complexes or organocatalysts. Among them, nucleophilic addition to carbon-carbon and carbon-nitrogen double bonds, α-functionalization of carbonyl compounds, allylic substitutions, and ring opening of oxiranes and aziridines are considered. The diastereodivergent synthesis of alkenes from alkynes is also included. Finally, stereodivergent intramolecular and intermolecular cycloadditions and other cyclizations are also reported.

Efficient synthesis of N-butadiene substituted oxindole derivatives

A novel rhodium(iii)-catalyzed amide carbonyl group directed alkenylation reaction between oxindoles and alkenes has been reported, which provides an efficient method for the synthesis of valuable and versatile functionalized N-(2E,4Z)-butadiene substituted oxindole derivatives.

Complete diastereodivergence in asymmetric 1,6-addition reactions enabled by minimal modification of a chiral catalyst

Catalytic systems that allow selective generation of any diastereomer of a reaction product bearing multiple stereocentres through minimal modification of a single catalyst scaffold remain elusive, particularly for carbon–carbon bond formations requiring simultaneous control of multiple selectivity factors. Here, we report a catalyst-directed pinpoint inversion of diastereochemical preference in the 1,6-addition of azlactones to δ-aryl dienyl carbonyl compounds with full control over other selectivities preserved. This rigorous diastereodivergence is enabled by the slight structural adjustment of a chiral iminophosphorane catalyst, providing access to all the stereoisomers with high regio-, distereo- and enantioselectivity. The utility of this method is demonstrated in the facile stereodivergent preparation of densely functionalized proline derivatives. The experimental and computational elucidation of the origin of the diastereodivergence is also reported.

For reactions producing numerous chiral centres, accessing all potential stereoisomers is synthetically appealing but difficult. Here, the authors report a stereodivergent 1,6-addition of azlactones where minimal changes to the catalyst structure switches the product selectivity.

A simple one-pot synthesis of 2,4-diaryl- 9H-pyrido[2,3-b]indoles under solvent-free conditions

A novel, simple, one-pot synthesis of 2,4-diaryl-9

Diastereo- and enantioselective phase-transfer alkylation of 3-substituted oxindoles with racemic secondary alkyl halides

A catalytic asymmetric alkylation of fully substituted enolates with racemic, non-activated secondary alkyl halides is described.

Switchable divergent asymmetric synthesis via organocatalysis

A variety of chiral organocatalysts, in addition to synergistic metal-based activation, were discussed in diverse switchable stereoselective reactions.

Imidazolylpyridine-In(OTf)3 catalyzed enantioselective allylation of ketimines derived from isatins

An enantioselective In(OTf)₃-catalyzed allylation of ketimines derived from isatins in the presence of an imidazolylpyridine ligand is described.