Progresses in organocatalytic asymmetric dearomatization reactions of indole derivatives

Organic Chemistry Frontiers, Journal Year: 2020, Volume and Issue: 7(23), P. 3967 - 3998

Published: Jan. 1, 2020

This review summarizes the progresses in organocatalytic asymmetric dearomatization reactions of indole derivatives and their applications total synthesis natural products, gives some insights into challenging issues this research field.

Language: Английский

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Tetracoordinate Boron Intermediates Enable Unconventional Transformations

Accounts of Chemical Research, Journal Year: 2021, Volume and Issue: 54(9), P. 2298 - 2312

Published: April 14, 2021

ConspectusOrganoboron compounds are a class of multifunctional reagents for the construction carbon–carbon and carbon–heteroatom bonds in modern synthetic chemistry. The transformations organoboron usually carried out through tetracoordinate boron intermediates mainly include additions to unsaturated bonds, rearrangement reactions, transmetalation so on. Although great progress has been achieved improving intermediates, there still shortcomings, such as sparse activation modes, paucity reaction strategies difficulties stereoselective control. In this Account, we discuss our recent advances development unconventional based on design including following three topics: (1) C–B bonds; (2) C–C (3) application chiral boron.The new build is interest chemists. We have developed tandem reactions involving multiple selective borylations alkynes synthesis stable boron, domino-borylation-protodeboronation (DBP) strategy alkynes, highly regio-, stereo-, chemoselective Cu-catalyzed diborylation β-CF3-1,3-enynes cascade B–Cl/C–B cross-metathesis C–H bond borylation triarylboranes. also novel form because formation an enduring theme organic disclosed long distance or migration coupling partners 1,4-migrations nitrile oxide nitrilium migrations isocyanide intermediate, palladium-catalyzed Suzuki–Miyaura thioureas thioamides, copper-catalyzed atroposelective Michael-type addition, Catellani reaction. Moreover, terms control found that tricoordinate complex could activate water with Brønsted acidity, which successfully applied high enantioselectivity asymmetric catalytic reduction challenging indoles.This Account summarizes efforts using not only precise wide range diverse but acid indoles.

Language: Английский

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Recent developments in enantio- and diastereoselective hydrogenation of N-heteroaromatic compounds

Organic & Biomolecular Chemistry, Journal Year: 2022, Volume and Issue: 20(9), P. 1794 - 1827

Published: Jan. 1, 2022

The enantioselective and diastereoselective hydrogenation of N-heteroaromatic compounds is an efficient strategy to access chirally enriched cyclic heterocycles, which often possess highly bio-active properties. This strategy, however, has only been established in recent times. part due the challenges high stability aromatic presence heteroatoms that have potential poison chiral catalysts. Additionally, are a structurally diverse family substrates, each group showing distinct reactivity hydrogenation. Advances years allowed various compounds, including pyridines, indoles, quinolines, isoquinolines, quinoxalines imidazoles, be hydrogenated with good excellent enantioselectivity under appropriate reaction conditions. Transition-metal catalysis, utilising iridium, ruthenium, rhodium, palladium complexes, found play important role this field. More recently, organocatalysis shown for certain compounds. review provides analysis developments importance these molecules their applications drug discovery highlighted throughout review.

Language: Английский

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Asymmetric Dearomatization of Indoles with Azodicarboxylates via Cascade Electrophilic Amination/Aza-Prins Cyclization/Phenonium-like Rearrangement

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(21), P. 11745 - 11753

Published: May 19, 2023

Herein, we report a highly efficient synthesis of enantioenriched aza-[3.3.1]-bicyclic enamines and ketones, class structural cores in many natural products, via asymmetric dearomatization indoles with azodicarboxylates. The reaction is initiated by electrophilic amination followed aza-Prins cyclization/phenonium-like rearrangement. A newly developed fluorine-containing chiral phosphoric acid displays excellent activity promoting this cascade reaction. absence or presence water as the additive directs pathway toward either enamine ketone products high yields (up to 93%) enantiopurity 98% ee). Comprehensive density functional theory (DFT) calculations reveal energy profile origins enantioselectivity water-induced chemoselectivity.

Language: Английский

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A diversity of recently reported methodology for asymmetric imine reduction

Organic Chemistry Frontiers, Journal Year: 2020, Volume and Issue: 7(20), P. 3312 - 3342

Published: Jan. 1, 2020

This review describes recent developments in enantioselective imine reduction, including related substrates which a CN bond is the target for and in situ methods.

Language: Английский

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Catalytic Atroposelective Catellani Reaction Enables Construction of Axially Chiral Biaryl Monophosphine Oxides

CCS Chemistry, Journal Year: 2021, Volume and Issue: 3(12), P. 377 - 387

Published: Jan. 18, 2021

Open AccessCCS ChemistryCOMMUNICATION1 Dec 2021Catalytic Atroposelective Catellani Reaction Enables Construction of Axially Chiral Biaryl Monophosphine Oxides Qiang Feng†, Xingxing Ma†, Wen Bao†, Shi-Jun Li, Yu Lan and Qiuling Song Feng† Institute Next Generation Matter Transformation, College Chemical Engineering, Material Sciences Huaqiao University, Xiamen 361021 †Q. Feng, X. Ma, W. Bao contributed equally to this work.Google Scholar More articles by author , Ma† Key Laboratory Molecule Synthesis Function Discovery, Chemistry, Fuzhou 350108 Bao† School Pharmacy, State Applied Organic Lanzhou 730000 Li Green Catalysis Center, Zhengzhou 450001 Google *Corresponding authors: E-mail Address: [email protected] Chemistry Chongqing Theoretical Computational 400030 https://doi.org/10.31635/ccschem.021.202000725 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail An unprecedented atroposelective reaction between phosphine oxide-containing aryl bromides, aryliodides, nucleophiles for the construction phosphine-containing biaryl atropisomers was established using an enantiopure norbornene derivative as chiral mediator. A broad range atropisomeric biaryl-based monophosphine oxides were obtained in good efficiency with excellent enantioselectivity. This set three component catalytic systems successfully inhibited two-component cross-couplings promoted formation aryl–aryl axis via a key Pd intermediate. Meanwhile, optically active two stereogenic axes also strategy. The synthetic utility methodology illustrated through further transformations into ligands which have been used applications asymmetric catalysis. In addition, detailed mechanism study DFT calculation conducted. Download figure PowerPoint Introduction phosphines are prevalent essential enantioselective transformations. Among all types phosphines, ones based on axially skeletons privileged structures.1,2 addition ubiquitous bidentate phosphines,3–8 monophosphines attracted great attention exhibit significant reactivity various catalysis (Figure 1a).9–15 It is well known that phosphorus compounds accessible from reduction oxides, more stable compatible under variable conditions; thus biaryls readily would be ideal protocol build phosphines. frameworks structural motifs biologically important natural products, therapeutic agents, materials besides constituting variety catalysts Therefore, assembly has aroused tremendous interest, versatile highly efficient strategies developed access such structures.16–37 Despite considerable research scaffolds, synthesis relatively rare 1b) usually requires elaborate routes, starting several-step transformations14 or building Suzuki–Miyaura couplings,15,38,39 fair enantiomeric excess (ee) values. 2016, Gu’s group40 disclosed palladium-catalyzed vinyl arene-based oxidized biaryls. Recently, Cramer co-workers23 reported elegant o-quinone diazides diphenylalkylphosphine oxides. Given importance monodentate synthesis, there few methods their preparation, development variant remains its infancy. Accordingly, general route desirable. Figure 1 | (a) Representative (b) Traditional (elusive). (c) Atropselective construct (this work). recent years, reaction41–48 emerged valuable multicomponent strategy motifs. Surprisingly, version scarcely probably due difficulty identifying appropriate ligand control enantioselectivity finding suitable components. 2018, Gu co-workers49 realized first ligand. et al.’s work,49 chirality installation took place last cross-coupling step involving achiral palladium (Pd) species. Motivated progress Pd/norbornene (NBE) cooperative functionalization both ortho- ipso-carbons arylhalides could achieved,50–56 especially Pd/chiral NBE employed synthesis,50,51 we envisioned establishment system iodide bromide Pd(II) intermediate 1c. Further trapping terminating nucleophile will render modular platform divergent enantioenriched 1c).57 Compared racemic reaction, our conjecture several challenges: first, selection competent reactants guaranteeing final product; second, choice proper capable affording intermediate, offers effective interaction atroposelectivity, third, balance stereoselectivity competitive reactions. Herein, report mediator materials. transformation features novel controlled instead ligands, materials, formation, substrate scope control. Experimental Methods details available Supporting Information. Results Discussion To validate feasibility continue long-term interest boron chemistry,58–63 1-iodonaphthalene ( 1a), (2-bromo-3-methylphenyl)-diphenylphosphine oxide 2a), phenylboronic acid chosen model substrates First, enantiopure-substituted NBEs prepared according literature procedures50,51; unfortunately, after careful condition screening (see Information Table S1 details), only n-propyl ester L3 demonstrated deliver desired product 57% NMR yield (48% isolated yield) 98% ee, Suzuki side products details). Considering alkenes widely third incorporation C=C bond increase functionality styrene 3a) replace reaction. After initial trials, pleased discover 4a 82% 93% ee CH3CN K2CO3 base at 110 °C 24 h combination Pd(OAc)2 (10 mol %)/methyl L1 (20 %) (Table 1, entry 1). Encouraged these results, L2– L9 evaluated entries 2–9), superior 85% (78% 99% 3). solvent temperature suggested optimal best 10–14). When amount reduced half, did not improve 15). We investigated other parameters, including different additives, bases, reagent ratios, concentration reactants, but results improve. most cases, values albeit low yields. Screening Conditions Entry Ligand Solvent Temperature (°C) Yield (%)a (%) 82 93 2 L2 84 98 3 85(78)b 99 4 L4 80 5 L5 71 97 6 L6 57 7 L7 Trace — 8 L8 9 32 10 Dioxane 49 50 11 Toluene 60 72 12 DMF 69 95 13 100 66 14 120 79 15c 74 90 aReaction conditions: 1a (0.1 mmol), 2a (2 equiv, 0.2 3a (2.5 0.25 %), L (2.0 mL), °C, h, determined 31P triphenylphosphine internal standard. DMF, dimethylformamide. bIsolated yield. cPd(OAc)2 (5.0 %). Substrate With conditions hand 3), generality obtain evaluated, summarized Schemes 1b. electrophiles 2) studied above conditions, corresponding target 4a–4d 51–78% yields enantiocontrol, indicating (2-bromo-3-methylphenyl)diphenylphosphine 1-iodo-2-isopropylbenzene presented result 4b). Subsequently, group styrenes examined partner standard 4e–4k) procured 62–95% (98–99% ee). them, para-chloro-substituted 4h, 95% ee), provides functional handle downstream elaborations. Naphthalene scaffold molecules; therefore, (1-bromonaphthalen-2-yl)diphenylphosphine probed together styrenes. Not surprisingly, expected once again moderate 4l–4p), unsubstituted demonstrating reactivity. Furthermore, aryliodides styrene; they delivered molecules ees 4q–4t). Other combinations components rendered satisfactory beautiful enantiocontrol 4u–4ad). Of note, diethyl (1-bromonaphthalen-2-yl)phosphonate proven candidate well, delivering 4ab synthetically useful might transformed activated olefins, acrylate esters coupling partners leading 4ac 4ad Scheme (a b) scope. (1.0 0.4 0.5 NBE* h. Yields given. examination reactions 1), bromides 2), styrenes, arylboronic acids, air, oxygen screened S1, substrates, showed inferior reactivities because multiple reactions, however, same 4ae–4ah). contain scaffolds64 constructed 4ah), represents unique feature transformation. Moreover, absolute configuration 4g, 4af, 4ah unambiguously confirmed X-ray crystallographic analysis, those assigned analogy. rotational barriers 4p, 4ac, 4af atropisomerization studies high-performance liquid chromatography (HPLC; see Based previous reports Pd/NBE-catalyzed halide-involved three-component reaction50–56 experience biaryls,59 plausible proposed follows (Scheme 2): Pd(0) inserts lead I, reacts form palladacycle complex II. undergoes oxidative oxide-bearing afford Pd(IV) III. reductive elimination β-carbon occurs IV regenerates V. V trapped procures biary-based 2). Plausible cycle. Density theory (DFT) calculations B3LYP/Def2-SVP understand atroposelectivity Pd-catalyzed As shown 2, starts coordinated species CP1, can react iodonaphthalene reactant process transition-state TS1 activation free energy 8.6 kcal/mol. Then, intermolecular insertion Pd(II)–C(naphthalenyl) takes TS2 free-energy barrier 20.0 kcal/mol CP4. exchange acetate leads reversible concerted-metalation-deprotonation (CMD)-type C–H generate five-membered CP6. coordination generates CP7 release acetic acid. Interestingly, inserted moiety environment around center. subsequent occur either top bottom position square planar Pd(II). calculated TS4 33.1 kcal/mol, 2.2 lower than face. five-coordinated pyramidal CP8 formed. rapid TS5 constructs new C(naphthalenyl)–C(phenyl) specific axial CP9. β-C(aryl) TS6 CP10 NBE. Sequentially, transmetallation TS7 TS8 4ae regeneration CP1 accomplish reveal processes 15 bromoarene onto value major coincident experimental observations. profiles (kcal/mol). clearly bromoarene, meanwhile, reacting DFT-calculated front-view geometry transitions TS4′ given 3a. formed NBE, evidently smaller bridged methylene below palladacycle. when place, likely occupy steric hindrance TS4. noncovalent (NCI) analysis transition states 3b) proved assumption. NCI plot TS4, no apparent ortho-methyl approaching it. Only weak hydrogen methyl observed. However, repulsion apparently observed TS4′. S-configuration kinetically favorable, consistent three-dimensional (3-D) structures transition-states possible repulsion. demonstrate practicality approach, gram-scale atropisomer 4l performed, proceeded smoothly give identical slight loss chemical 3a, 71% yield, 97% yielded, respectively, without erosion stereochemical integrity cleavage P=O presence HSiCl3 diisopropylethylamine (DIPEA) (Schemes 3b). These monophosphines-bearing allylations 3c 3d). Scale-up transformation; (c d) applications. Conclusion system. bromide, iodide, (arylalkenes acids) candidates transformation, method ligands. enantioselectivities, scalability, formation. mechanisms validated calculations. expansion currently underway laboratory. includes 1H NMR, 13C HRMS, products. Conflict Interest authors declare competing financial interest. 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Previous articleNext article FiguresReferencesRelatedDetails Issue AssignmentVolume 3Issue 12Page: 377-387Supporting Copyright & Permissions© 2021 Chinese SocietyKeywordsCatellani reactionaxial chiralityatroposelectivitybiarylsbiaryl oxidesAcknowledgmentsFinancial Downloaded 3,285 times PDF DownloadLoading ...

Language: Английский

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Asymmetric Hydrogenation of Racemic 2-Substituted Indoles via Dynamic Kinetic Resolution: An Easy Access to Chiral Indolines Bearing Vicinal Stereogenic Centers

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(8), P. 5081 - 5087

Published: Feb. 15, 2024

The asymmetric hydrogenation (AH) of N-unprotected indoles is a straightforward, yet challenging method to access biologically interesting NH chiral indolines. This has for years been limited 2/3-monosubstituted or 2,3-disubstituted indoles, which produce indolines bearing endocyclic centers. Herein, we have reported an innovative Pd-catalyzed AH racemic α-alkyl aryl-substituted indole-2-acetates using acid-assisted dynamic kinetic resolution (DKR) process, affording range structurally fascinating that contain exocyclic stereocenters with excellent yields, diastereoselectivities, and enantioselectivities. Mechanistic studies support the DKR process relies on rapid interconversion each enantiomer substrates, leveraged by acid-promoted isomerization between aromatic indole nonaromatic enamine intermediate. reaction can be performed gram scale, products derivatized into non-natural β-amino acids via facile debenzylation amino alcohol upon reduction.

Language: Английский

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Catalytic Enantioselective Synthesis of Spirooxindoles by Oxidative Rearrangement of Indoles

Angewandte Chemie International Edition, Journal Year: 2020, Volume and Issue: 60(11), P. 5871 - 5875

Published: Dec. 7, 2020

Oxidative rearrangement of indoles to access oxindoles has been used as a key step in complex molecule synthesis. We report catalytic enantioselective variant this transformation by chiral phosphoric acid catalysis, providing rapid range enantioenriched spirooxindoles. The high enantioselectivity is controlled dynamic kinetic resolution.

Language: Английский

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Chiral Phosphoric Acids as Versatile Tools for Organocatalytic Asymmetric Transfer Hydrogenations

European Journal of Organic Chemistry, Journal Year: 2021, Volume and Issue: 2021(38), P. 5367 - 5381

Published: Oct. 14, 2021

Herein, recent developments in the field of organocatalytic asymmetric transfer hydrogenation (ATH) C=N, C=O and C=C double bonds using chiral phosphoric acid catalysis are reviewed. This still rapidly growing area relies on metal-free catalysts combination with biomimetic hydrogen sources. Chiral acids have proven to be extremely versatile tools this area, providing highly active enantioselective alternatives for reduction α,β-unsaturated carbonyl compounds, imines various heterocycles. Eventually, such transformations more often used multicomponent/cascade reactions, which undoubtedly shows their great synthetic potential bright future hydrogenations.

Language: Английский

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Enantioselective Copper-Catalyzed sp²/sp³ Diborylation of 1-Chloro-1-Trifluoromethylalkenes

ACS Central Science, Journal Year: 2022, Volume and Issue: 8(8), P. 1134 - 1144

Published: July 20, 2022

Fluorine-containing organoboron compounds have emerged as novel building blocks in chemical synthesis; among them, fluorinated sp

Language: Английский

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