Asymmetric Allylic Substitution Research Articles

Pd-Catalyzed Asymmetric Allylic Substitution Cascade via Desymmetrization for the Construction of Chiral Polyheterocycles

Chiral polyheterocycles represent an important class of compounds because of their prevalence in bioactive natural products and chiral drugs. Pd-catalyzed allylic substitution is a powerful synthetic tool for forming C–C and C–X bonds (X = N, O, S, etc.). Naturally, asymmetric cascade reactions that utilize allylic substitution are undoubtedly efficient pathways to construct heterocycles. In this article, we reviewed the Pd-catalyzed asymmetric allylic substitution cascade via the desymmetrization of meso-diol diesters of cycloolefins, for the construction of chiral polyheterocycles and their derivatives.

Rh-Catalyzed Asymmetric Allylic Substitution with Photo-Generated Alkyl Radical Species

Rh-Catalyzed Asymmetric Allylic Substitution with Photo-Generated Alkyl Radical Species

Palladium‐Catalyzed Asymmetric Allylic Substitutions Achieved by C–N Axially Chiral N‐Arylpyrrole Derived Monophosphine Ligands

Monophosphine ligands based on C–N axially chiral N‐Arylpyrrole backbones are prepared starting from amino acids and evaluated in Pd‐catalyzed asymmetric allylic substitutions. 20.7‐ 99.9% ees are achieved in the reactions of rac‐1,3‐diphenylallyl acetates with O‐, N‐ and C‐nucleophiles. Ligand screening revealed that the steric hindrance from 3‐ or 4‐ position of the pyrrole is crucial for the enantioselectivity of the reaction. The synthetic utilization of the products was demonstrated by the transformation of one product by a gold‐catalyzed oxidative rearrangement reaction.

Iridium-Catalyzed Asymmetric and Stereoinvertive Allylic Substitution with Chiral Boronic Esters

Iridium-Catalyzed Asymmetric and Stereoinvertive Allylic Substitution with Chiral Boronic Esters

Application of mixed phosphorus/sulfur ligands based on terpenoids in Pd-catalyzed asymmetric allylic substitution and Rh-catalyzed hydrogenation.

A small library of easily prepared diamidophosphite-sulfides based on 1,3-thioether alcohols, primarily of terpenoid nature, was developed. Upon complexation with Pd(II) ions, these hemilabile ligands showed the ability to form both P,S-chelates and complexes with two ligands P-monodentately bonded to the metal. The structures of the ligands and their complexes were determined by 2D NMR spectroscopy and X-ray diffraction. The use of these stereoselectors provided up to 95% ee in the classic Pd-catalyzed asymmetric allylic substitution reactions of (E)-1,3-diphenylallyl acetate with C- and N-nucleophiles and up to 80% ee in the Pd-mediated allylic alkylation of cinnamyl acetate with β-ketoesters. In addition, ee values of up to 90% with quantitative conversion were achieved in the Rh-catalyzed asymmetric hydrogenation of methyl esters of unsaturated acids. The effects of the structural parameters, reaction conditions and ligand-to-metal ratio on the catalytic results are discussed.

Origin of Stereoselectivity in Pd-Catalyzed Asymmetric Allylic Substitutions with Trost-Type Mixed Bidentate Phosphorus Ligands

Origin of Stereoselectivity in Pd-Catalyzed Asymmetric Allylic Substitutions with Trost-Type Mixed Bidentate Phosphorus Ligands

Rhodium-Catalyzed Asymmetric N2-C5 Allylation of Indazoles with Dienyl Allylic Alcohols.

The development of site-selective and regio- and enantioselective reactions of substrates with multiple active sites is an important topic and remains a substantial challenge in synthetic chemistry. Here, we describe a rhodium-catalyzed asymmetric N2-C5 allylation of indazoles with dienyl allylic alcohols under mild conditions. In the presence of a Rh/(P/olefin) catalyst and formic acid, chiral N2-C5 allylic indazoles were formed in good yields with excellent enantioselectivities (up to 97% ee). The mechanism proceeds through an elusive intermediate Int B, which represents a challenging task on asymmetric allylic substitution (AAS) of dienyl substrates.

Synthesis of C-N Axially Chiral N-Arylbenzo[g]indoles via a Central-to-Axial Chirality Conversion Strategy.

Gold-catalyzed cascade cyclization of diynes for the synthesis of previously unexplored C-N axially chiral N-arylbenzo[g]indoles was described. The transformation was achieved via a central-to-axial chirality conversion strategy. The chiral conversion exhibited high efficiency. Besides single C-N chiral axis, N-arylbenzo[g]indoles bearing both C-N and C-C chiral axes were also afforded. The title compound derived monophosphine ligand was prepared and was evaluated in Pd-catalyzed asymmetric allylic substitutions, showing excellent chiral induction ability.

Dual-Catalysis-Enabled Construction of Vicinal Stereogenic Centers through Diastereo- and Enantioselective Allylic Substitution

AbstractVicinal stereogenic centers represent prevalent structural motifs in organic synthetic chemistry, and their construction poses a longstanding challenge. Transition-metal-catalyzed asymmetric allylic substitution has become a well-established enantioselective C–C bond-forming reaction. When these reactions involve a prochiral nucleophile and an allylic electrophile with a terminal substituent, the creation of vicinal stereogenic centers becomes feasible. However, despite remarkable achievements having been accomplished, realizing this transformation with precise control over both the enantio- and diastereoselectivity remains a significant challenge. To address the stereoselective challenges, the introduction of a second catalyst to the transition-metal-catalyzed asymmetric allylic alkylation to control the diastereoselectivity during C–C bond formation has proven particularly fruitful. In this short review, we aim to highlight recent advances in dual catalysis that enable diastereo- and enantioselective allylic substitutions.1 Introduction2 Construction of Vicinal Stereogenic Centers by Organo and Metal Dual Catalysis2.1 Chiral Phase-Transfer Catalysis and Transition-Metal Dual Catalysis2.2 Chiral Amine and Transition-Metal Dual Catalysis2.3 NHC and Transition-Metal Dual Catalysis2.4 Chiral Aldehyde and Transition-Metal Dual Catalysis2.5 Chiral Lewis Base and Transition-Metal Dual Catalysis3 Construction of Vicinal Stereogenic Centers by Metal and Metal Dual Catalysis3.1 Lewis Acidic Metal and Iridium Dual Catalysis3.2 Lewis Acidic Metal and Palladium Dual Catalysis3.3 Palladium and Ruthenium Dual Catalysis3.4 Other Advancements in the Construction of Vicinal Stereogenic Centers through Synergistic Bimetallic Catalysis Enabling Asymmetric Allylic Alkylation4 Conclusions and Future Outlook

Asymmetric Allylic Substitution Reactions Based on Relay Catalysis

AbstractTransition-metal-catalyzed asymmetric allylic substitution reactions represent a hot research topic in the field of asymmetric synthesis, with significant progress having been made. Among diverse catalysis systems, relay catalysis enables sequential activation of multiple steps in one pot and the rapid construction of multiple chiral centers, providing a simple and powerful platform for organic synthesis. Recently, relay catalysis has been successfully applied to asymmetric allylic substitution reactions, and a variety of challenging transformations have been realized. This Short Review summarizes the related progress on asymmetric allylic substitution reactions based on relay catalysis over the last decade.1 Introduction2 The General Transformation Model3 Allylation Relays Further Reaction4 Initial Reaction Relays Allylation5 Conclusion and Outlook

Tridentate Sulfoxide-N-olefin Hybrid Ligands in Rhodium-Catalyzed Asymmetric Allylic Substitution.

A well-defined tridentate chiral sulfoxide-N-olefin ligand has been designed and applied in rhodium-catalyzed asymmetric allylic substitutions of racemic allylic carbonates, providing the branched allylic products in good yields with good to high enantioselectivities and excellent regioselectivities. This reaction mechanism, which involves the possible hemilability of olefin coordination on sulfoxide-N-olefin hybrid ligands with rhodium, is elaborated as well.

Z-Retentive Asymmetric Allylic Substitution Reactions of Aldimine Esters under Ru/Cu Dual Catalysis.

Ru/Cu dual catalysis has been applied for Z-retentive asymmetric allylic substitution reactions of aldimine esters. This reaction provides an enantioselective synthesis of chiral Z-olefins in high yields (up to 91% yield) with excellent enantioselectivity (up to 98% ee) under mild conditions. The previously unreacted trisubstituted allylic electrophiles under Ir catalytic system are found to be compatible, affording the stereoretentive products in either Z- or E-form. Both linear and branched allylic electrophiles are suitable substrates with excellent reaction outcomes. Notably, Ru and Cu complexes are added in one-pot and simplifies the manipulation of this protocol and self-sorting phenomena could be observed in this Ru/Cu dual catalytic system.

TADDOL-based P,S-bidentate phosphoramidite ligands in palladium-catalyzed asymmetric allylic substitution.

A series of easy-to-prepare and modular chiral P,S-bidentate phosphoramidites were synthesized. With respect to Pd(II), these ligands showed the ability to form stable P,S-chelate allylic complexes. The structures of the ligands and their complexes were confirmed by 2D NMR spectroscopy and single-crystal X-ray diffraction. These chiral inducers provided up to 99% ee in the Pd-catalyzed asymmetric allylic substitution of (E)-1,3-diphenylallyl acetate with C- and N-nucleophiles and up to 94% ee in the Pd-mediated allylic alkylation of cinnamyl esters with β-ketoesters and 2,5-dimethylpyrrole. Furthermore, up to 92% ee with quantitative conversion and chemo- and regioselectivity was achieved in the rare reaction between 2-(diethoxyphosphoryl)-1-phenylallyl acetate and aniline. The effects of the structural parameters, reaction conditions and ligand-to-metal ratio on the catalytic results are discussed. It was shown that the ligands surpass their analogues with different denticity.

Chiral P,N,N-Ligands for Pd-Catalyzed Asymmetric Allylic Substitutions

Chiral P,N,N-Ligands for Pd-Catalyzed Asymmetric Allylic Substitutions

Palladium-catalyzed regio- and stereo-selective phosphination of cyclic biarylsulfonium salts to access atropoisomeric phosphines.

A palladium-catalyzed regio- and stereo-selective phosphination of cyclic biarylsulfonium salts (racemic) with HPAr3Ar4 for straightforward synthesis of atropoisomeric phosphines (P,S-ligands) bearing a stereogenic axis or both a stereogenic axis and a P-stereogenic center is reported. The high reactivity and regio- and stereo-selectivity originate from the torsional strain release and palladium catalysis, and the construction of a P-stereogenic center is enabled by an efficient dynamic kinetic resolution. The high performance of the nascent P,S-ligands has been demonstrated in palladium-catalyzed asymmetric allylic substitutions, indicating the great potential of the present methodology.

Copper-catalyzed asymmetric allylic substitution of racemic/meso substrates

This review focuses on the advancements in Cu-catalyzed asymmetric allylic substitution using racemic/meso substrates, detailing the ligands used, the scope of nucleophiles, the underlying dynamic processes, and their practical applications.

Construction of Enantioenriched Quaternary C-Cl Oxindoles through Palladium-Catalyzed Asymmetric Allylic Substitution with Chloroenolates.

A palladium-catalyzed asymmetric chloroenolate allylation with vinyl benzoxazinanones under mild reaction conditions has been developed, affording a series of optically active 3,3-disubstituted oxindoles exhibiting a chloro-group and a linear aryl amino side chain in good yields with up to 96% ee. Versatile functional group tolerance on the benzene ring has been demonstrated, and the utility of this method was probed by a scale-up synthesis and highlighted by product derivatizations.

The Evolution of Phosphite‐Oxazoline Ligands for the Pd‐Allylic Substitution and Their Application in Building Chiral Molecules

AbstractPd‐catalyzed asymmetric allylic substitution (AAS) is a highly effective method for producing chiral molecules with alkene‐substituted frameworks which can be further derivatized. However, its stereochemical outcome is affected by the steric requirements of the substrate and only a narrow set of nucleophiles yield excellent enantioselectivities. In this regard, phosphite‐oxazolines have emerged as strong candidates to be privileged ligands for this process, providing results that surpass most of the previously published studies. They have provided high enantiocontrol when used in the Pd‐AAS of several hindered and unhindered substrates, using a wide range of C‐, O‐, and N‐nucleophiles. In this concept, we review and discuss the current progress made in the design of tailor‐made phosphite‐oxazoline ligand libraries for the Pd‐AAS of a broad range of substrates and nucleophiles and its application in the construction of chiral complex molecules.

Synergistic catalysis for stereocontrol of prochiral nucleophiles in palladium-catalyzed asymmetric allylic substitution

Synergistic catalysis for stereocontrol of prochiral nucleophiles in palladium-catalyzed asymmetric allylic substitution

Stereodivergent Construction of 1,3‐Chiral Centers via Tandem Asymmetric Conjugate Addition and Allylic Substitution Reaction

AbstractHerein, we report a synthesis of cyclohexanones bearing multi‐continuous stereocenters by combining copper‐catalyzed asymmetric conjugate addition of dialkylzinc reagents to cyclic enones with iridium‐catalyzed asymmetric allylic substitution reaction. Good to excellent yields, diastereoselectivity and enantioselectivity can be obtained. Unlike the stereodivergent construction of adjacent stereocenters (1,2‐position) reported in the literature, the current reaction can achieve the stereodivergent construction of nonadjacent stereocenters (1,3‐position) by a proper combination of two chiral catalysts with different enantiomers.