Ligand‐Free and Reusable Palladium Nanoparticles‐Catalyzed Alkylation of 2‐Alkylazaarenes with Activated Ketones under Neutral Conditions DOI

Naziya Parveen,

Alagesan Muthukumar,

Govindasamy Sekar

et al.

Advanced Synthesis & Catalysis, Journal Year: 2019, Volume and Issue: 361(18), P. 4255 - 4277

Published: July 6, 2019

Abstract A mild, efficient, and stable binaphthyl‐stabilized palladium nanoparticles (Pd−BNP) catalyzed ( sp 3 )C−H reaction of 2‐alkylazaarenes with activated carbonyl compounds was developed. Various such as α‐keto amide, isatin, 1,2‐diketone, ester, trifluoromethyl ketone, phenylglyoxal derivatives were examined most the underwent smoothly to provide corresponding products in moderate excellent yields. Moreover, chemoselective reactions amides presence simple ketones achieved. Also, model extended a gram‐scale synthesis some utilized for derivatization form N ‐oxides, acryl 1,2‐diol, respectively. The major advantages protocol are neutral conditions, no additional requirement external ligand, successful reusability Pd−BNP catalyst up five cycles without losing its activity yield. Hg‐poisoning hot filtration tests confirmed heterogeneity catalyst. magnified image

Language: Английский

Chiral guanidines and their derivatives in asymmetric synthesis DOI
Shunxi Dong, Xiaoming Feng, Xiaohua Liu

et al.

Chemical Society Reviews, Journal Year: 2018, Volume and Issue: 47(23), P. 8525 - 8540

Published: Jan. 1, 2018

Over the past two decades, chiral guanidines and their derivatives have emerged as one of most powerful organocatalysts mainly on basis strong basicity and/or hydrogen-bond donor ability. Structurally diverse guanidine catalysts (bicyclic, monocyclic acyclic types) sprang up enabled numerous fundamental organic transformations to be realized in high efficiency stereoselectivity. Moreover, guanidinium salts were successfully employed H-bond catalysis, phase-transfer catalysis others. Recently, several novel [e.g., salt, pentanidium, bis(guanidino)iminophosphorane] been designed used for synthesis valuable molecules. In addition, combination with cationic or anionic metal species dramatically expanded utility provided solutions challenging importance which cannot achieved conventional catalysts. This article reviews current achievements organocatalysis, updates versatile guanidine-metal salt combinations asymmetric catalytic reactions. representative examples achiral guanidine-related are also covered.

Language: Английский

Citations

146
Activating Pronucleophiles with High pKa Values: Chiral Organo‐Superbases DOI

Yu‐Hui Wang,

Zhong‐Yan Cao, Qinghua Li

et al.

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 59(21), P. 8004 - 8014

Published: Dec. 2, 2019

Abstract Direct deprotonation represents an extremely simple, straightforward, and atom‐economic strategy to activate pronucleophiles bearing acidic proton. However, the difficulty often arises in activating with high p K a values by using conventional chiral tertiary amines. To overcome this challenge, handful of novel Brønsted superbases, including amidines, guanidines, cyclopropenimines, iminophosphoranes, have been discovered recent years. This minireview focuses on application these organo‐superbases catalytic asymmetric reactions weakly pronucleophiles, highlights their comparison amines, demonstrating highly efficient processes stereoselectivity controlled conversions superbases. The advantage new superbases brings great opportunity for developing more transformations pronucleophiles.

Language: Английский

Citations

59
Phosphorus‐Containing Superbases: Recent Progress in the Chemistry of Electron‐Abundant Phosphines and Phosphazenes DOI Creative Commons
Robin F. Weitkamp, Beate Neumann, Hans‐Georg Stammler

et al.

Chemistry - A European Journal, Journal Year: 2021, Volume and Issue: 27(42), P. 10807 - 10825

Published: May 25, 2021

The renaissance of Brønsted superbases is primarily based on their pronounced capacity for a large variety chemical transformations under mild reaction conditions. Four major set screws are available the selective tuning basicity: nature basic center (N, P, …), degree electron donation by substituents to central atom, possibility charge delocalization, and energy gain hydrogen bonding. Within past decades, plethora neutral electron-rich phosphine phosphazene bases have appeared in literature. Their outstanding properties advantages over inorganic or charged now made them indispensable as auxiliary deprotonation processes. Herein, an update chemistry phosphines phosphazenes given. In addition, due widespread interest, use catalysis ligands coordination highlighted.

Language: Английский

Citations

43
Catalytic Enantioselective Synthesis of α‐Chiral Azaheteroaryl Ethylamines by Asymmetric Protonation DOI
Chao Xu,

Calum W. Muir,

Andrew G. Leach

et al.

Angewandte Chemie International Edition, Journal Year: 2018, Volume and Issue: 57(35), P. 11374 - 11377

Published: June 29, 2018

Abstract The direct enantioselective synthesis of chiral azaheteroaryl ethylamines from vinyl‐substituted N‐heterocycles and anilines is reported. A phosphoric acid (CPA) catalyst promotes dearomatizing aza‐Michael addition to give a prochiral exocyclic aryl enamine, which undergoes asymmetric protonation upon rearomatization. reaction accommodates broad range N‐heterocycles, nucleophiles, substituents on the centre, generating products in high enantioselectivity. DFT studies support facile nucleophilic based catalyst‐induced LUMO lowering, with site‐selective, rate‐limiting, intramolecular proton transfer ion‐paired intermediate.

Language: Английский

Citations

53
Recent Advances in Synthesis of Chiral Thioethers DOI
Hongyi Chen, Wenlong Jiang, Qingle Zeng

et al.

The Chemical Record, Journal Year: 2020, Volume and Issue: 20(11), P. 1269 - 1296

Published: Sept. 15, 2020

Abstract Chiral thioethers is an important class of organosulfur molecules with extensive applications, especially in the field medicine and organic synthesis. This review discusses recent progress synthesis enantioenriched chiral hopes to be helpful for related research future. It summarized from compounds‐participating reaction types, including nucleophilic substitution, cross coupling, sulfa‐Michael addition, sulfenylation, asymmetric allylic reaction, Doyle‐Kirmse Pummerer‐type rearrangement, Smiles [2,3] Stevens Sommelet‐Hauser rearrangement.

Language: Английский

Citations

47
Enantioselective Protonation: Hydrophosphinylation of 1,1‐Vinyl Azaheterocycle N‐Oxides Catalyzed by Chiral Bis(guanidino)iminophosphorane Organosuperbase DOI
Saikat Das,

Qiupeng Hu,

Azusa Kondoh

et al.

Angewandte Chemie International Edition, Journal Year: 2020, Volume and Issue: 60(3), P. 1417 - 1422

Published: Oct. 8, 2020

Abstract Enantioselective protonation by hydrophosphinylation of diarylphosphine oxides with 2‐vinyl azaheterocycle N ‐oxide derivatives was demonstrated using chiral bis(guanidino)iminophosphorane as the higher‐order organosuperbase catalyst. It confirmed several control experiments that a weak conjugate acid bis(guanidino)iminophosphorane, instead achiral oxides, directly functioned proton source to afford corresponding product in highly enantioselective manner most cases. generated from would broaden scope reaction systems because utilization range less acidic pronucleophiles. This method is highlighted valuable synthesis series P,N‐ligands for metal complexes through reduction phosphine oxide and units without loss enantiomeric purity.

Language: Английский

Citations

43
Iridium‐Catalyzed Asymmetric Allylic Substitution of Methyl Azaarenes DOI
Xi‐Jia Liu,

Wen‐Yun Zhang,

Chao Zheng

et al.

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(20)

Published: March 3, 2022

Abstract Herein, an Ir‐catalyzed asymmetric allylic substitution reaction of methyl azaarenes is described. Azaarenes such as (benzo)thiazole, oxazole, benzoimidazole, pyridine, and (iso)quinoline are all tolerated. The corresponding chiral azaarene derivatives obtained in good yields with high enantioselectivity (up to 96 % yield 99 ee). utilization the Knochel reagent TMPZnBr⋅LiBr warrants situ formation benzylic nucleophiles without additional activating reagents. 1 H NMR studies suggested a two‐fold function this reaction. synthetic utility method has been showcased by concise enantioselective synthesis allosteric protein kinase modulator.

Language: Английский

Citations

25
Borane-Catalyzed Enantioselective α-Alkylation of Unactivated 2-Alkylbenzoxazoles with Electron-Deficient Olefins DOI

Chongren Ai,

Lu Liu, Xiaochen Wang

et al.

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(35), P. 24663 - 24669

Published: Aug. 20, 2024

Chiral borane–catalyzed reactions have recently emerged as a powerful tool for the enantioselective production of chiral scaffolds. In this study, we demonstrated first time that bisborane catalyst can be used α-functionalization 2-alkylazaarenes; specifically, accomplished unprecedented highly α-alkylation unactivated 2-alkylbenzoxazoles with electron-deficient olefins. The strong Lewis acidity and steric bulk were essential to observed reactivity selectivity.

Language: Английский

Citations

5
Development of Chiral Ureates as Chiral Strong Brønsted Base Catalysts DOI
Azusa Kondoh, Sho Ishikawa, Masahiro Terada

et al.

Journal of the American Chemical Society, Journal Year: 2020, Volume and Issue: 142(8), P. 3724 - 3728

Published: Feb. 11, 2020

Recently, chiral Brønsted bases having high basicity have emerged as a powerful tool in developing new catalytic enantioselective reactions. However, such strong base catalysts are still very scarce. Herein, we report the development of anionic N,N′-dialkyl ureate moiety basic site. Its prominent activity was demonstrated addition reactions α-thioacetamides less acidic pronucleophiles with various electrophiles. Thus, newly developed catalyst accessibility and structural tunability would expand scope viable transformations under catalysis.

Language: Английский

Citations

33
Development of Molecular Transformations on the Basis of Catalytic Generation of Anionic Species by Organosuperbase DOI Open Access
Azusa Kondoh, Masahiro Terada

Bulletin of the Chemical Society of Japan, Journal Year: 2021, Volume and Issue: 94(1), P. 339 - 356

Published: Jan. 1, 2021

Abstract In this account, we summarized our recent efforts to develop molecular transformations under Brønsted base catalysis on the basis of own guiding principles for designing reaction systems, that include “the generation and application anionic species which are difficult utilize in conventional systems” employment organosuperbases possessing much higher basicities than organic bases as a catalyst”. particular, discussed reactions involving carbanions less acidic compounds through formal umpolung process from carbonyl [3+2] cycloadditions synthetic equivalent 1,3-dipole epoxide opening.

Language: Английский

Citations

29