The Role of Alkali Metal in α‐MnO₂ Catalyzed Ammonia‐Selective Catalysis

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 58(19), P. 6351 - 6356

Published: March 18, 2019

The unexpected phenomenon and mechanism of the alkali metal involved NH3 selective catalysis are reported. Incorporation K+ (4.22 wt %) in tunnels α-MnO2 greatly improved its activity at low temperature (50-200 °C, 100 % conversion NOx vs. 50.6 over pristine 150 °C). Experiment theory demonstrated atomic role incorporated . Results showed that could form a stable coordination with eight nearby O sp3 atoms. columbic interaction between trapped atoms can rearrange charge population Mn atoms, thus making topmost five-coordinated unsaturated cations (Mn5c , Lewis acid sites) more positive. Therefore, positively charged Mn5c better chemically adsorb activate molecules compared counterpart, which is crucial for subsequent reactions.

Language: Английский

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Iridium‐Catalyzed Hydrochlorination and Hydrobromination of Alkynes by Shuttle Catalysis

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 59(7), P. 2904 - 2910

Published: Nov. 26, 2019

Described herein are two different methods for the synthesis of vinyl halides by a shuttle catalysis based iridium-catalyzed transfer hydrohalogenation unactivated alkynes. The use 4-chlorobutan-2-one or tert-butyl halide as donors hydrogen allows this transformation in absence corrosive reagents, such acid chlorides, thus largely improving functional-group tolerance and safety profile these reactions compared to state-of-the-art. This method has granted access alkenyl compounds containing acid-sensitive groups, tertiary alcohols, silyl ethers, acetals. synthetic value those methodologies been demonstrated gram-scale where low catalyst loading was achieved.

Language: Английский

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Synergistic Lewis acid-base sites of ultrathin porous Co3O4 nanosheets with enhanced peroxidase-like activity

Nano Research, Journal Year: 2021, Volume and Issue: 14(10), P. 3514 - 3522

Published: July 5, 2021

Language: Английский

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Enantioselective Olefin Hydrocyanation without Cyanide

Journal of the American Chemical Society, Journal Year: 2019, Volume and Issue: 141(47), P. 18668 - 18672

Published: Nov. 5, 2019

The enantioselective hydrocyanation of olefins represents a conceptually straightforward approach to prepare enantiomerically enriched nitriles. These, in turn, comprise or are intermediates the synthesis many pharmaceuticals and their synthetic derivatives. Herein, we report cyanide-free dual Pd/CuH-catalyzed protocol for asymmetric Markovnikov vinyl arenes anti-Markovnikov terminal which oxazoles function as nitrile equivalents. After an initial hydroarylation process, oxazole substructure was deconstructed using [4 + 2]/retro-[4 2] sequence afford enantioenriched product under mild reaction conditions.

Language: Английский

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Overcoming Selectivity Issues in Reversible Catalysis: A Transfer Hydrocyanation Exhibiting High Kinetic Control

Journal of the American Chemical Society, Journal Year: 2020, Volume and Issue: 142(25), P. 10914 - 10920

Published: June 1, 2020

Reversible catalytic reactions operate under thermodynamic control, and thus, establishing a selective system poses considerable challenge. Herein, we report reversible transfer hydrocyanation protocol that exhibits high selectivity for the thermodynamically less favorable branched isomer. Selectivity is achieved by exploiting lower barrier C–CN oxidative addition reductive elimination at benzylic positions in absence of cocatalytic Lewis acid. Through design novel type HCN donor, practical, branched-selective, HCN-free was realized. The synthetically useful resolution mixture linear nitrile isomers also demonstrated to underline value reactions. In broader context, this work demonstrates kinetic can be reactions, thus opening new horizons their synthetic applications.

Language: Английский

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Recent progress in transition-metal-catalyzed hydrocyanation of nonpolar alkenes and alkynes

Organic & Biomolecular Chemistry, Journal Year: 2019, Volume and Issue: 18(3), P. 391 - 399

Published: Dec. 5, 2019

Hydrocyanation is a powerful method for the preparation of nitriles which are versatile building blocks synthesis amines, acids and amides.

Language: Английский

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Arene C–H Iodination Using Aryl Iodides

CCS Chemistry, Journal Year: 2021, Volume and Issue: 4(6), P. 1889 - 1900

Published: June 28, 2021

Open AccessCCS ChemistryCOMMUNICATION6 Jun 2022Arene C–H Iodination Using Aryl Iodides Shangda Li†, Chunhui Zhang†, Lei Fu, Hang Wang, Cai, Xiaoxi Chen, Xinchao Wang and Gang Li Li† Key Laboratory of Coal to Ethylene Glycol Its Related Technology, Center for Excellence in Molecular Synthesis, Fujian Institute Research on the Structure Matter, Chinese Academy Sciences, Fuzhou, 350002 , Zhang† Fu Cai Chen *Corresponding author: E-mail Address: [email protected] Frontiers Science Transformative Molecules, Shanghai Jiao Tong University, 200240 https://doi.org/10.31635/ccschem.021.202101156 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Metathesis reactions represent powerful synthetic tools that have been used a number fields from synthesis natural product functional material preparation. However, metathesis reaction is extremely rare. Herein, we report first Pd(II)-catalyzed iodination arenes using 2-nitrophenyl iodides as mild iodinating reagents via formal reaction. Unusual C–I bond formation occurred with aryl preference competing C–C coupling this Assisted by aliphatic carboxyl directing groups, range hydrocinnamic acids related could be selectively iodinated at either meta- or ortho-positions phenyl ring. Remote diastereoselective activation was also promising. This method might unfold novel approach iodinate challenging substrates. Download figure PowerPoint Introduction The exploration cleave reorganize chemical bonds continuous pursuit organic chemists.1,2 In recent years, significant advances achieved study isodesmic reactions, which often use user-friendly exhibit good group tolerance.3–29 Of particular note, Morandi group3 Arndtsen group4 independently reported between aroyl chlorides Pd(0)/Pd(II) catalysis (Scheme 1a),30–34 enabling chlorides. catalytic two unknown.1 Importantly, functionalization rare.22–29 To best our knowledge, transition-metal-catalyzed intermolecular has not realized date.22–24 Thus, development (formal) highly attractive, it utilize readily available offer strategy generate sophisticated iodides, attainable conventional methods. Scheme 1 | (a–d) metathesis. are extensively arylating through exclusive reductive elimination (RE), favored over RE metal-center 1b).35–45 Notably, Whitfield Sanford46 carbon–halogen bond-forming Pd(IV) complex yield chloride 2007 1c). such reaction.47–60 During previous Pd-catalyzed remote meta-C–H arylation iodide, detected ∼10% side product.61 Inspired unexpected discovery, envisioned successful carboiodination reactions34 oxidants activation,62–67 would introduce mechanistically distinct pathway halogenation reactions. past decade, site-selective become an essential synthesizing versatile, valuable chemicals cross-coupling reactions.68–88 Yu's group70,71 Dai's group72 few pyridine-based templates. Nonetheless, classes still limited,68–88 most them electrophilic IOAc generated I2 PhI(OAc)2 AgOAc,89 lead unwanted reduces site-selectivity overall Therefore, exploring complementary reagent able eliminate desirable. unprecedented 1d). ortho- commercially iodides. possible. Results Discussion Initially, amide 1a′ (Table 1) bearing meta-directing template substrate investigate since desired had obtained study.61 Moreover, iodination70–72 very limited narrow scope,90–107 class important core structure biologically active molecules drug, Baclofen. encountered difficulties eliminating undesired 1a′. 1a designed new substrate, prepared large scale known β-amino acid (see Supporting Information). Pleasingly, almost eliminated while optimize reaction, possibly due better chelating ability Information comparison). After extensive tuning conditions Information), products 2a obtained, 85% combined involving iodide Pd(OAc)2 pyridine-type L1 ligand, presence AgOAc (0.5 equiv) K2HPO4 hexafluoroisopropanol (HFIP), set 100 °C 24 h (entry 1). Note methylation original product, easier isolation. Approximately 0.1 mmol nitrobenzene proton nuclear magnetic resonance (1H NMR). represented example suggests Pd center decreased dramatically without pyridone L1, indicating played crucial role 2). dual role: (1) accelerate cleavage step acting internal base like acetate surrogate, (2) stabilize catalyst effectively forming stable reducing Pd's reactivity meantime.108 Other ligands electron-deficient ligand L2 were evaluated led comparable bit higher turnover than 3), but lower pyridin-2-ol 4). N-mono-protected amino N-Ac-L-Phe-OH promote less effective 5). addition silver salt necessary, amount feasible (entries 6–10), exact clear present. Surprisingly, although believed promoting removal,47,48 detectable equiv 8) though trace 2 9). Utilizing Na2CO3 beneficial, other bases K2CO3 gave yields 11–13). Solvents evaluated, HFIP proved suitable. Subsequently, superior catalysts tested 16 17). sensitive temperature, markedly 90 °C, compared under parallel 18). addition, loading 19). meta-selectivity generally excellent, only regioisomers during optimization conditions. Evaluation indicated electron-withdrawing ortho-substitution critical, no one identified (bottom). oxidative conjoint electronic weakly coordinating effect.109–111 weak coordination nitro rather strong (compared 2-iodobenzoic acid) center, critical preventing Pd(IV).62,65–68 Although rationale present, above suggested carboxyl-based dominating preference, relate steric/electronic properties iodide. additive achieving Table S1 contrast, mainly para-iodination products, together meta-isomer, observed direct iodination, para-isomers N-Iodosuccinimide (NIS) I2, 1,3-diiodo-5,5-dimethylhydantoin (DIH) decomposed substrate. Optimization Arene Reaction Conditionsa Entry Deviation Standard Conditions Yield (%) [mono/di] None 85 [3.3/1] Without [1/0] 3 instead 83 [1.9/1] 4 Pyridin-2-ol 70 [2.7/1] 5 78 [2.9/1] 6 45 7 0.25 80 [3/1] 8 1.0 75 9 2.0 74 [3.6/1] 10 Ag2CO3 82 [3.1/1] 11 39 12 81 13 Na2HPO4 76 [2.8/1] 14 t-Amyl-OH N.D. 15 TFE 43 Pd(TFA)2 73 [4.2/1] 17 PdCl2(MeCN)2 61 [5.8/1] 18 57 19 1.5 66 [5.6/1] Note: N.D., detected. aReaction conditions: scale, (1 mL), air; MeI (0.2 mmol), (0.3 mmol). determined 1H NMR CH2Br2 standard. Part by-product removed rotavapor Unless otherwise noted, both traces gas chromatography–mass spectrometry (GC-MS) flame ionization detector (FID). bA little cDetected GC-MS, (from I2/PhIOAc). With optimized hand, protocol series isolated 2amonoand 2adi high (81%); employed delight, generally, average mono-substituted substrates -donating groups ( 2b–2l; 49–82%). halides 2f 2k) bromide 2g 2l) tolerated, providing opportunity synthesize diversely substituted arenes. para-substituted low products. Furthermore, di-substitution 2m) substituting alkyl chain 3-phenyllactic derivative 2n; 52%) allowed. Finally, structurally biphenylcarboxylic 2o– 2q; 65–71%) benzyl alcohol 2r; 50%) derivatives meta-positions. selectivity excellent amounts regioisomers, observed. smoothly cleaved acidic Scope iodination. standard conditions, deviation: 48 h. Isolated yields. aL1 used. b24 cOptical pure (<99% ee) 1n; 2nmono calculated after hydrolysis. dAbout 10% di-product, isolated. Since ortho-iodinated compounds, moved test generality ortho-C–H acids. their native free exceptionally scarce, scope examples limited,112–114 requirement 7-membered metallacycle. Based careful investigation Tables S2–S4 details), 3, 4a) (93%) 1-iodo-4-methoxy-2-nitrobenzene, N-Formyl-Gly-OH AgOBz (0.1 NaOAc equiv). robust, leading broad 4a– 4r; 62–93%). More complicated 4s; 87%), phenylalanine 4t; 68%), drug Baclofen 4u; 51%) give 1-iodo-4-methoxy-2-nitrobenzene (0.4 (0.02 (0.04 (2 h, air. ayield scale. b10% (o,m)-di-product isolated, see Information. cSOCl2/MeOH methylation, As asymmetric rare challenging,115,116 curious optical induce desymmetrization. preliminary 4), diastereoselectivity (up d.r. = 90.5/9.5, 6bmono) 5-bromopyridin-2-ol ligand. absolute configuration 6amono removal X-ray crystallography 7). present even study; thus, further required. Diastereoselective potential methods briefly (Schemes 5a–5c). Cross-coupling proceeded 2amono afford meta-substituted 8– 10). Besides, chiral 11) efficiently produced derivative. 12. (a–c) Synthetic elaborations arene gain insight into mechanism, mechanistic studies conducted. First, C–H/C–I exchange excess 6a 6b), suggesting reversible more control reactions). Second, inspired Daugulis's work,47 performed Pd(0) catalyst; did any Pd(II) intermediate unlikely 6c). C(aryl)–I required bulky reaction.30–34 salt.65–68 Third, hard us detect much modifying when methyl 2-iodobenzoate 6d, variations). involved iodide.47–53 three types subjecting 2-phenyl phenol 6e), where dibenzofuran oxidant enable C–O if utilized.117–119 These results Schemes 6c–6e support selective current experiments excluding slow release iodine carried out (a–e) Mechanistic works47–53,61 studies, proposed cycle outlined 7, follows: A exchange. coordinate κ1 κ2 mode, latter mode facilitate approaching ring giving B. Then meta-position metalation deprotonation process,120 its best-matched distance geometry, affording palladacycle C. Oxidative C gives D. D, act play inhibit RE; facilitating 2amono-H arylated E. Such effect ortho-substituent Chen's 2-methoxy C–N enantioselective intramolecular C(sp3)–H amidation reaction.62 protonolysis E regenerates nitrobenzene. reduction oxidizing minor pathway. generation consistent protonation predominantly sources solvent deuterated substrate); viewed For similar, except cyclopalladation ortho-position F). pathways Pd(II)/Pd(III) excluded stage;57,58 hence, being actively out, course. Proposed Conclusion We developed Two assisted groups. stimulate developing uncover way application currently underway laboratory. includes general experimental procedures characterization spectra. Conflict Interest authors declare financial interest. Preprint Statement An early version manuscript posted preprint server ChemRxiv before publication CCS Chemistry. corresponding article can found here: http://dx.doi.org/10.26434/chemrxiv.14449668 Acknowledgments gratefully thank supports NSFC (grant nos. 22022111 22071248), Natural Foundation Province 2020J02008 2020J01108), Youth Innovation Promotion Association Sciences no. 2020306), Strategic Priority Program XDB20000000). References 1. Bhawal N.; B.Catalytic Isofunctional Reactions-Expanding Repertoire Shuttle Reactions.Angew. Chem. Int. Ed.2019, 58, 10074–10103. Google Scholar 2. Transfer Functionalization Catalysis.ACS Catal.2016, 6, 7528–7535. 3. Lee Y. H.; B.Metathesis-Active Ligands Enable Catalytic Functional Group Aroyl Chlorides Iodides.Nat. Chem.2018, 10, 1016–1022. 4. De La Higuera Macias M.; A.Functional Transposition: Palladium-Catalyzed Ar-X σ-Bonds Acid Chloride Synthesis.J. Am. Soc.2018, 140, 10140–10144. 5. 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B.; Zou Liu Huang H.Palladium-Catalyzed Ring-Closing C-N Rapid Construction Saturated N-Heterocycles.J. Soc.2020, 142, 18341–18345. 21. N-Heterocycles Aminodienes N,O-Acetals.J. Org. Chem.2021, 86, 7849–7863. 22. Rochette E.; Desrosiers V.; Soltani Fontaine G.Isodesmic C-H Borylation: Perspectives Proof Concept Borylation Catalysis.J. 12305–12311. 23. Garcia F.-G.Boron Recycling Metal-Free Terminal Heteroarenes.ACS 11046–11056. 24. N.Palladium-Catalyzed Direct Phosphole Derivatives Triarylphosphines Carbon-Hydrogen Bonds.Angew. Ed.2013, 52, 11892–11895. 25. Chung Vo Hein E.Copper-Catalyzed Hydrogen/Iodine Exchange 1-Iodoalkynes.ACS Catal.2017, 2505–2510. 26. Shao J.; X.Lanthanide-Catalyzed Alkynyl Carbon-Carbon Single-Bond Secondary Amino Group.Angew. Ed.2016, 55, 11485–11489. 27. Lv X.-Y.; Xiao L.-J.; Xie J.-H.; Q.-L.Alkenyl Allylamines vi

Language: Английский

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Lewis Acid Catalyzed Transfer Hydromethallylation for the Construction of Quaternary Carbon Centers

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 58(43), P. 15386 - 15389

Published: Aug. 26, 2019

The design and gram-scale synthesis of a cyclohexa-1,4-diene-based surrogate isobutene gas is reported. Using the highly electron-deficient Lewis acid B(C

Language: Английский

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Hydroarylation of Alkenes by Protonation/Friedel–Crafts Trapping: HFIP-Mediated Access to Per-aryl Quaternary Stereocenters

The Journal of Organic Chemistry, Journal Year: 2019, Volume and Issue: 84(22), P. 14965 - 14973

Published: Oct. 21, 2019

Upon treatment with a combination of HFIP and an organic sulfonic acid, alkenes behave as Brønsted bases protonate to give carbocations which can be trapped by electron-rich arenes. The reaction constitutes Friedel–Crafts hydroarylation proceeds Markovnikov selectivity is orthogonal traditional metal-catalyzed processes. Intermolecular transfer hydrogenation hydrothiolation under analogous conditions are also demonstrated.

Language: Английский

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Nickel-Catalyzed Markovnikov Transfer Hydrocyanation in the Absence of Lewis Acid

Organic Letters, Journal Year: 2020, Volume and Issue: 22(11), P. 4456 - 4460

Published: May 11, 2020

Hydrocyanation in the absence of toxic HCN gas is highly desirable. Addressing that challenge, transition-metal-catalyzed transfer hydrocyanation using safe precursors has been developed, but these reagents generally require a Lewis acid for activation, and control regioselectivity often remains problematic. In this Letter, Ni-catalyzed Markovnikov-selective operates any reported. The readily prepared pro-aromatic 1-isopropylcyclohexa-2,5-diene-1-carbonitrile used as source, reaction shows broad substrate scope high functional group tolerance. Terminal styrene derivatives, dienes, internal alkynes are converted with good to excellent selectivities. Mechanistic studies provide insights into origin regioselectivity.

Language: Английский

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