Addition Of Arylboronic Acids Research Articles

Quaternary Chiral Phthalides Enabled by Dirhodium(II)/Phosphine Catalyzed Asymmetric Carbonyl Addition Cascade.

The catalytic asymmetric synthesis of chiral phthalides has garnered considerable interest. However, the construction of phthalides with a chiral quaternary carbon stereocenter still remains challenging. In this study, we developed a new strategy toward catalytic asymmetric synthesis of chiral 3,3-disubstituted phthalides via a dirhodium(II)/phosphine-catalyzed carbonyl addition cascade, yielding phthalides with up to 97% ee values. The reaction proceeded through dirhodium(II)/phosphine-catalyzed asymmetric carbonyl addition of arylboronic acids to isoquinoline-1,3,4(2H)-triones, followed by base-mediated ring contraction.

Cu-Catalyzed Asymmetric Arylation of Enone Diesters with Arylboronic Acids.

The Cu-catalyzed asymmetric conjugate addition of arylboronic acids to enone diesters is reported. This operationally simple and scalable reaction proceeded under mild conditions. The practical utility of this approach was demonstrated by the synthesis of structurally important γ-lactones and a cyclopentene that bear an aryl group. Mechanistic studies revealed that two different copper catalytic species work synergistically in the reaction.

Rhodium‐Catalyzed N‐Arylation Addition of Arylboronic Acids to Ketimines

Comprehensive SummaryHerein, we report rhodium catalyzed N‐arylation via addition of arylboronic acids to electron‐deficient α‐iminoesters which can be prepared in high efficiency by using easily accessible β‐carbonyl esters. The reaction is highly regiospecific to achieve the N‐aryl addition efficiently with up to 99% yield under mild conditions. The corresponding product can be further efficiently converted into indoles and a series of other important building blocks.

Palladium-Catalyzed Stereocontrolled Synthesis of Aryl-C-Glycosides from Arylboronic Acids and Glycal Enones Through 1,4-Conjugate Addition Reactions

Abstract1,4-Conjugate addition of arylboronic acids to the glycal enones delivered 2-deoxy-α-aryl-C-glycosides in good yields. The reaction was catalyzed by palladium acetate in the presence of trifluoroacetic acid and 1,10-phenanthroline. A wide range of glycal enones derived from d-glucal, d-galactal, and d-rhamnal participated in the coupling reaction with different arylboronic acids smoothly. Different protecting groups including benzyl, acetyl, pivaloyl, and benzoyl were compatible under optimized conditions.

Addressing polar solvent challenges in the heterogenization of palladium catalysed Hayashi-Miyaura reaction on polymer support

The development of recyclable heterogeneous catalysts for the palladium-catalysed additions of arylboronic acids to nitrostyrenes is investigated in this study. Two strategies, direct copolymerization and post-modification, are explored for immobilizing chiral isoquinoline-oxazoline ligands onto polymer matrices. Various copolymer formulations are prepared, and their catalytic activity, recyclability, and reaction kinetics are evaluated. The incorporation of polar functional groups into the polymer matrix enhances catalytic properties, albeit with a decrease in reaction rate compared to the homogeneous system. Post-modification using a polystyrene-polyethylene glycol (PS-PEG) support shows promise, resulting in a moderate decrease in reaction rate and satisfactory performance over multiple reaction cycles. The findings provide valuable insights into the immobilization of chiral ligands and highlight the advantages and limitations of different polymer compositions. These results contribute to the development of advanced catalytic systems for the synthesis of biologically relevant compounds.

Immobilization of Trifluoromethyl-Substituted Pyridine-Oxazoline Ligand and Its Application in Asymmetric Continuous Flow Synthesis of Benzosultams.

This study presents an improved synthetic route to ligand (S)-4-(tert-butyl)-2-(5-(trifluoromethyl)pyridin-2-yl)-4,5-dihydrooxazole and its application as a highly active and enantioselective catalyst in the addition of arylboronic acids to cyclic N-sulfonylketimines. Immobilization of such a ligand was achieved using a commercially available starting material and a PS-PEG TentaGel S NH2 support, resulting in a stable heterogeneous catalyst. Although the anchored catalyst exhibited a slight reduction in enantioselectivity and a 4-fold decrease in reaction rate, it displayed remarkable stability, enabling 10 consecutive reaction cycles. Furthermore, the successful transition to a continuous flow system demonstrated even higher turnover numbers compared to batch arrangements. These findings provide valuable insights into the development of efficient flow reactors for continuous synthesis of benzosultams, further advancing the field of asymmetric catalysis.

Synthesis and neuroprotective activity of 3-aryl-3-azetidinyl acetic acid methyl ester derivatives.

A library of 3-aryl-3-azetidinyl acetic acid methyl ester derivatives was prepared from N-Boc-3-azetidinone employing the Horner-Wadsworth-Emmons reaction, rhodium(I)-catalyzed conjugate addition of arylboronic acids, and subsequent elaborations to obtain N-unprotected hydrochlorides, N-alkylated and N-acylated azetidine derivatives. The compounds were evaluated for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activity, revealing several derivatives to possess AChE inhibition comparable to that of the AChE inhibitor rivastigmine. The binding mode of the AChE inhibitor donepezil and selected active compounds 26 and 27 within the active site of AChE was studied using molecular docking. Furthermore, the neuroprotective activity of the prepared compounds was evaluated in models associated with Parkinson's disease (salsolinol-induced) and aspects of Alzheimer's disease (glutamate-induced oxidative damage). Compound 28 showed the highest neuroprotective effect in both salsolinol- and glutamate-induced neurodegeneration models, and its protective effect in the glutamate model was revealed to be driven by a reduction in oxidative stress and caspase-3/7 activity.

Pd-Catalyzed Regioselective (Markovnikov) Addition of Aryl Boronic Acids to Terminal Alkynes of 1,3-Dicarbonyl Compounds and Cyclization/Debenzoylation of Olefinic Dicarbonyl: Access to Arylated Pyran and (E)-4-Methylene-1,6-diphenylhex-5-en-1-one.

This Letter outlines palladium-catalyzed regioselective (Markovnikov's) addition of aryl boronic acids to propargyl 1,3-dicarbonyl alkyne to accomplish olefinic/diene 1,3-dicarbonyl compounds without the need for water workup. This methodology showcases remarkable performance with wide-ranging substrate diversity, achieving high yields while employing merely 3 mol % [Pd] alongside a mild KOAc base. Moreover, the utility of dicarbonyl olefins is exemplified through their application in intramolecular cyclization and debenzoylation reactions to access valuable trisubstituted pyran building blocks and (E)-4-methylene-1,6-diphenylhex-5-en-1-one synthesis.

Palladium-Catalyzed Asymmetric Conjugate Addition of Arylboronic Acids to α,β-Unsaturated Lactams: Enantioselective Construction of All-Carbon Quaternary Stereocenters in Saturated Nitrogen-Containing Heterocycles.

Stereogenic nitrogen-containing heterocycles are ubiquitous in natural products and pharmaceutical compounds, but methods for their enantioselective construction have remained elusive. We report a general method for the asymmetric conjugate addition of arylboronic acids to β-alkyl/aryl α,β-unsaturated lactams that affords chiral β,β-disubstituted lactams. The transformation is operationally simple and air- and moisture-tolerant and uses a commercially available (S)-t-Bu-PyOx ligand. The method is high-yielding (up to 95% yield) and enantioselective (up to 97% ee) for a wide range of arylboronic acids and α,β-unsaturated lactams, including those with different ring sizes.

Pd(II)/N,N′-Disulfonyl bisimidazoline-catalyzed asymmetric arylation of isoquinoline-1,3,4-trione-derived ketimines

A palladium/chiral N,N′-disulfonyl bisimidazoline (Bim)-catalyzed asymmetric addition of arylboronic acids to isoquinoline-1,3,4-trione-derived ketimines is reported, leading to the generation of a series of functionalized isoquinoline-1,3(2H,4H)-diones bearing one quaternary carbon-amino functionality in good to excellent yields with ≥95% ee in most cases. The reaction has remarkable compatibility with both substrate scopes, providing a highly enantioselective entry to chiral heterocyclic α-tertiary amines.

Confronting the Challenge of Asymmetric Carbonyl Addition to Sterically Bulky Isatins: Upgrading Dirhodium(II)/Biphosphine Catalytic System

Catalytic asymmetric addition of arylboronic acids to ketones is a powerful transformation for directly delivering chiral tertiary alcohols. However, there is no successful example of enantioselective addition to steric bulky isatins, which contain bulky substituent at the 4-position. To confront this challenge, in this work a dirhodium/(BTFM-Garphos) system was developed that showed extremely high activity and stereoselectivity, and the reactions were usually finished within a few minutes.

Synthesis and Antimicrobial Activity of the Pathogenic E. coli Strains of p-Quinols: Additive Effects of Copper-Catalyzed Addition of Aryl Boronic Acid to Benzoquinones.

A mild and efficient protocol for the synthesis of p-quinols under aqueous conditions was developed. The pivotal role of additives in the copper-catalyzed addition of aryl boronic and heteroaryl boronic acids to benzoquinones was observed. It was found that polyvinylpyrrolidone (PVP) was the most efficient additive used for the studied reaction. The noteworthy advantages of this procedure include its broad substrate scope, high yields up to 91%, atom economy, and usage of readily available starting materials. Another benefit of this method is the reusability of the catalytic system up to four times. Further, the obtained p-quinols were characterized on the basis of their antimicrobial activities against E. coli. Antimicrobial activity was further compared with the corresponding 4-benzoquinones and 4-hydroquinones. Among tested compounds, seven derivatives showed an antimicrobial activity profile similar to that observed for commonly used antibiotics such as ciprofloxacin, bleomycin, and cloxacillin. In addition, the obtained p-quinols constitute a suitable platform for further modifications, allowing for a convenient change in their biological activity profile.

Enantioselective rhodium-catalyzed addition of arylboronic acids to N-heteroaryl ketones: synthesis of α-hydroxy acids.

The enantioselective addition of arylboronic acids to N-heteroaryl ketones provides a convenient access to chiral α-heteroaryl tertiary alcohols, yet addition reactions of this type have been challenging due to catalyst deactivation. In this report, an efficient rhodium-catalyzed addition of arylboronic acids to N-heteroaryl ketones is established, affording a variety of valuable α-heteroaryl alcohols with excellent functional group compatibility. The employment of the WingPhos ligand containing two anthryl groups is crucial for this transformation. In particular, a range of chiral benzoxazolyl-substituted tertiary alcohols were formed with excellent ee values and yields by employing a Rh loading as low as 0.3 mol%, which can serve as a practical protocol to furnish a series of chiral α-hydroxy acids after hydrolysis.

Double approaches for obtaining an asymmetric one-pot addition/reduction reaction

In the last decades, one of the most important goals in synthetic chemistry consists in having both a low environmentally impact process and a more economic one. Based on this consideration, the one-pot reaction represents a valid alternative to realize this challenge, thanks to its decreasing of energy and time consumption, avoiding a lengthy separation process for purification of the chemical intermediates. The here proposed one-pot reaction consists in a first step involving an asymmetric conjugate addition of aryl boronic acids to 3-azaarylpropenones containing pyridine core followed by an asymmetric transfer hydrogenation of the aryl ketone in the case of biaryl moieties and by an asymmetric biocatalytic reduction in the case of alkyl derivatives. Studying the kinetic of the first reaction, the second catalytic step can be successfully carried out with good results in terms of conversion and stereoselectivity with both the approaches.

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The cover picture shows that the enantioselective construction of 6‐4 carbocyclic scaffolds with ring‐junction all‐carbon stereocenters has been achieved through Pd(II)/chiral N,N’‐disulfonyl bisimidazoline (Bim) ligand‐catalyzed asymmetric reaction of yne‐allenones and arylboronic acids. In this reaction, realization of 6‐6‐4 carbocyclic skeletons with high chemo‐, regio‐ and enantio‐selectivities is a one‐step process from benzene‐linked yne‐allenones while synthesizing 6‐4 skeleton is a two‐step process, which begins with intramolecular [2 + 2] reaction of alkyl‐tethered yne‐allenones, followed by Pd catalyzed asymmetric addition of arylboronic acids to cyclic enones generated in the first step. DFT calculations have been applied to understand these reaction processes. More details are discussed in the article by Jiang et al. on page 1767—1776.image

Pd(II)‐Catalyzed Asymmetric Addition of Arylboronic Acids to Aliphatic N‐Carbamoyl Hydrazones

AbstractCatalysts generated by combinations of Pd(TFA)2 and pyridine‐hydrazone ligands have been applied to 1,2 addition of arylboronic acids to aliphatic N‐carbamoyl (Cbz) hydrazones, affording protected α‐aryl monoalkylhydrazines with high enantioselectivities (37‐99% ee). Subsequent removal of the benzyloxy carbonyl protecting group provides a direct entry to free monosubstituted hydrazines, key building blocks for the synthesis of appealing 1,2‐diaza‐heterocycles, aminoacid derived hydrazides and other pharmacophores thereof.magnified image

Selective Synthesis of Ketones and Chiral Allylic Alcohols from the Addition of Arylboronic Acids to α,β-Unsaturated Aldehydes Mediated by a Transition Metal/Monophosphorus Ligand System.

Here, we demonstrated a transition metal-mediated/monophosphorus ligand system for the selective synthesis of ketones or chiral allylic alcohols in high yields/enantiomeric excess from the 1,2-addition of arylboronic acids to α,β-unsaturated aldehydes. Notably, isomerization of the chiral allylic alcohols to ketones was suppressed by the Ru-catalyzed/monophosphorus ligand system. The asymmetric catalytic system provides an alternative and efficient method of preparing chiral allylic alcohols.

Ru-Catalyzed Asymmetric Addition of Arylboronic Acids to Aliphatic Aldehydes via P-Chiral Monophosphorous Ligands.

Chiral alcohols are among the most widely applied in fine chemicals, pharmaceuticals and agrochemicals. Herein, the Ru-monophosphine catalyst formed in situ was found to promote an enantioselective addition of aliphatic aldehydes with arylboronic acids, delivering the chiral alcohols in excellent yields and enantioselectivities and exhibiting a broad scope of aliphatic aldehydes and arylboronic acids. The enantioselectivities are highly dependent on the monophosphorous ligands. The utility of this asymmetric synthetic method was showcased by a large-scale transformation.

Catalytic Enantioselective Construction of 6‐4 Ring‐Junction All‐Carbon Stereocenters and Mechanistic Insights

Comprehensive SummaryDeveloping reactions for the synthesis of 6‐6‐4 and 6‐4 carbocyclic scaffolds with a chiral quaternary center at the bridgehead position is highly desired, considering the existence of such skeletons in natural products with biological activities and the potential of using these molecules for downstream studies in chemical biology and medicinal chemistry. Report here is accessing these target skeletons with high chemo‐, regio‐ and enantio‐selectivities through Pd(II)/chiral N,N’‐disulfonyl bisimidazoline (Bim) ligand‐catalyzed asymmetric reaction of yne‐allenones and arylboronic acids. Realization of 6‐6‐4 skeleton with a ring‐junction all‐carbon stereocenter is a one‐step process while synthesizing 6‐4 skeleton is a two‐step process, which begins with intramolecular [2 + 2] reaction of allenes with alkynes, followed by Pd‐catalyzed asymmetric addition of arylboronic acids to cyclic enones generated in the first step. Noteworthy is that chiral Bim ligand as a C2‐symmetric N,N’‐bidentateanionic ligand, designed by us, in coordinating with Pd catalyst was first applied to catalyze asymmetric 1,4‐conjugate addition reaction with the high catalytic performance (the reaction can be carried out in air). DFT calculations have been applied to understand how these reactions take place, the origins of enantioselectivity, and relative reactivities of different substrates.

Rhodium catalyzed asymmetric synthesis of Chiraphos derivatives

Herein, we report a highly efficient versatile synthetic route to Chiraphos derivatives through Rh/Ph-bod catalyzed asymmetric addition of aryl boronic acids to phosphinyl dienes. Various substituted phosphinyl dienes, both on the parent skeleton and the phosphine atoms, were well tolerated with this method and provided chiral phosphine oxides in satisfied yield and up to 95% ee. The corresponding Chiraphos derivative displayed an advantage over Chiraphos in the representative Pd-catalyzed asymmetric 1,4-addition reaction.