In Situ NMR and Kinetics Reveal Origins of Regioselectivity Differences for Epichlorohydrin Ring-Opening in Lewis and Brønsted Acid Zeolites DOI
David W. Flaherty, David M. Potts, Huston Locht

и другие.

Research Square (Research Square), Год журнала: 2025, Номер unknown

Опубликована: Апрель 30, 2025

Abstract Altering the quantities and organization of reactive species at active sites enables control turnover rates regioselectivities (rate ratios) for ring-opening epichlorohydrin (C3H5ClO) across two orders magnitude. Kinetic analysis suggests that parallel monomolecular (SN1) bimolecular (SN2) substitution mechanisms contribute to observed C3H5ClO reactions with methanol (CH3OH) over both Lewis (Sn-BEA) Brønsted acid (Al-BEA) zeolites in liquid solvents. In situ solid-state 13C-nuclear magnetic resonance spectroscopy (SS-NMR) measurements give direct evidence proposed ring-opened carbocations activated CH3OH intermediates these catalysts. Interpretation time-resolved operando 13C-SS-NMR spectra show C3H5ClO-derived CH3OH-derived surface convert products through SN1 SN2 reaction subsequently form distinct produce regioisomers. These NMR also reveal a concomitant shift from increases coverage achieved by local concentrations CH3OH, C3H5ClO, diluting CH3CN. This knowledge provides new insight into roles confinement on regioselectivity catalytic organic solid-liquid interfaces.

Язык: Английский

Stereoselective gem-C,B-Glycosylation via 1,2-Boronate Migration DOI

Wei-Cheng Zhao,

Ruipeng Li, Chao Ma

и другие.

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(6), С. 2460 - 2467

Опубликована: Фев. 3, 2022

A novel protocol is established for the long-standing challenge of stereoselective geminal bisglycosylations saccharides. The merger PPh3 as a traceless glycosidic leaving group and 1,2-boronate migration enables simultaneous introduction C–C C–B bonds at anomeric stereogenic center furanoses pyranoses. power this method showcased by set site-selective modifications glycosylation products construction bioactive conjugates skeletons. scarce metal-free 1,1-difunctionalization process alkenes also concomitantly demonstrated.

Язык: Английский

Процитировано

18
Enantioselective Alkylation of Unactivated C–O Bond: Solvent Molecule Affects Competing β-H Elimination and Reductive Elimination Dynamics DOI
Tingting Sun, Jintong Zhang, Yijun Fang

и другие.

ACS Catalysis, Год журнала: 2023, Номер 13(6), С. 3702 - 3709

Опубликована: Март 1, 2023

Despite the fact that metal-catalyzed asymmetric alkylative cross-couplings have been well-established, enantioselective substitution of an unactivated C–O bond remains a challenge due to lack strategies cleave and suppress β-H elimination as well control stereochemistry simultaneously. Herein, activation with β-H-containing alkylating reagents was described using chiral nickel catalyst, versatile axially biaryls bearing alkyl moieties different chain lengths were delivered in good yields high ee. Control experiments demonstrated significant role solvent tetrahydrofuran facilitate this transformation. DFT calculations revealed coordination THF Mg(II) is pivotal for suppressing during reductive elimination, thus unlocking how molecule affects competing dynamics transition-metal-catalyzed cross-coupling reactions.

Язык: Английский

Процитировано

11
Neighboring‐Group Participation by C‐2 Acyloxy Groups: Influence of the Nucleophile and Acyl Group on the Stereochemical Outcome of Acetal Substitution Reactions DOI Creative Commons
Y. S. CHUN, Wouter A. Remmerswaal, Jeroen D. C. Codée

и другие.

Chemistry - A European Journal, Год журнала: 2023, Номер 29(57)

Опубликована: Июль 6, 2023

A single acyloxy group at C-2 can control the outcome of nucleophilic substitution reactions pyran-derived acetals, but extent neighboring-group participation depends on a number factors. We show here that does not necessarily stereochemical acetal with weak nucleophiles. The 1,2-trans selectivity increased increasing reactivity incoming nucleophile. This trend suggests intermediacy both cis-fused dioxolenium ions and oxocarbenium in stereochemistry-determining step. In addition, as electron-donating ability neighboring decreased, preference for products increased. Computational studies how barriers ring-opening reaction transition states to provide change capacity C-2-acyloxy

Язык: Английский

Процитировано

10
Reprogramming the Transition States to Enhance C–N Cleavage Efficiency of Rhodococcus opacus l-Amino Acid Oxidase DOI Creative Commons
Yaoyun Wu,

Yaozhong Cui,

Wei Song

и другие.

JACS Au, Год журнала: 2024, Номер 4(2), С. 557 - 569

Опубликована: Янв. 16, 2024

l

Язык: Английский

Процитировано

4
Catalytic Orthogonal Glycosylation Enabled by Enynal‐Derived Copper Carbenes DOI
Surya Pratap Singh, Bidhan Ghosh, Indrajeet Sharma

и другие.

Advanced Synthesis & Catalysis, Год журнала: 2024, Номер 366(8), С. 1847 - 1856

Опубликована: Фев. 17, 2024

Abstract Herein, we present an approach for catalytic orthogonal glycosylation utilizing earth‐abundant copper carbenes. This method operates under mild conditions and employs readily accessible starting materials, including benchtop stable enynal‐derived glycosyl donors, synthesized at the gram scale. The reaction accommodates a variety of acceptors, primary, secondary, tertiary alcohols. carbenes exhibit remarkable reactivity selectivity, allowing formation glycosidic linkages with different protecting groups stereochemical patterns. provides access to both 1,2‐ cis ‐ trans ‐glycosidic linkages. product stereoselectivity is independent anomeric configuration donor, which also has widely used alkynes thioglycoside donors. An iterative synthesis trisaccharide further demonstrates application this reactivity.

Язык: Английский

Процитировано

4
Unveiling the Role of Solvent in Solution Phase Chemical Reactions using Deep Potential-Based Enhanced Sampling Simulations DOI

Anmol Jindal,

Tarak Karmakar

The Journal of Physical Chemistry Letters, Год журнала: 2024, Номер unknown, С. 9932 - 9938

Опубликована: Сен. 23, 2024

We have used a deep learning-based active learning strategy to develop

Язык: Английский

Процитировано

4
Backside versus Frontside SN2 Reactions of Alkyl Triflates and Alcohols DOI Creative Commons
Wouter A. Remmerswaal, Tjeerd de Jong, Koen N. A. van de Vrande

и другие.

Chemistry - A European Journal, Год журнала: 2024, Номер 30(25)

Опубликована: Фев. 22, 2024

Nucleophilic substitution reactions are elementary in organic chemistry that used many synthetic routes. By quantum chemical methods, we have investigated the intrinsic competition between backside S

Язык: Английский

Процитировано

3
Role of ion pairs in model glycosylation reactions of permethylated glucosyl and xylosyl triflates DOI

Hana Sakai,

Sae Tsushida,

Takashi Hosoya

и другие.

Carbohydrate Research, Год журнала: 2024, Номер 544, С. 109227 - 109227

Опубликована: Авг. 8, 2024

Язык: Английский

Процитировано

3
Stereoelectronic Effect of Protecting Groups on the Stability of Galactosyl Donor Intermediates DOI Creative Commons
R. W. M. Kwok,

Ryan Rutkoski,

Pavel Nagorny

и другие.

Molecules, Год журнала: 2025, Номер 30(2), С. 218 - 218

Опубликована: Янв. 7, 2025

Using methods of DFT, we investigated the effect electron withdrawing and donating groups on relative stability tentative glycosyl donor reaction intermediates. The calculation shows that by changing stereoelectronic properties protecting group, can influence dioxolenium type intermediates up to 10 kcal mol−1, increasing nucleophillicity 4-O-Bz intermediate becomes more stable than a triflate–donor pair. We exploited this mechanism design galactosyl donors with custom O2 O4, outcome cyclohexanol. showed no change in product distribution, which suggests neighboring group participation takes precedence over remote due kinetic barriers.

Язык: Английский

Процитировано

0
Isothiourea – catalyzed α-selective glycosylations DOI Creative Commons

Bhaswati Ghosh,

Charles Enlow,

Zhengyue Ma

и другие.

Chemical Communications, Год журнала: 2025, Номер unknown

Опубликована: Янв. 1, 2025

Here, we disclose the discovery that isothioureas efficiently catalyze formation of both α-1,2- cis and trans glycosyl linkages from either bromide or chloride donors, furnishing glycosides in good to complete selectivities.

Язык: Английский

Процитировано

0