Construction of all-carbon quaternary center by NHC-catalyzed Heck-type C–H tertiary alkylation

Tetrahedron Chem, Journal Year: 2025, Volume and Issue: unknown, P. 100124 - 100124

Published: Feb. 1, 2025

Language: Английский

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Mechanism and Origins of Regio- and Stereoselectivities of NHC-Catalyzed Dearomative Annulation of Benzoazoles and Cinnamaldehydes from DFT

The Journal of Physical Chemistry A, Journal Year: 2025, Volume and Issue: unknown

Published: March 5, 2025

A theoretical study on the mechanism, regioselectivity, and enantioselectivity of NHC-catalyzed dearomatizing annulation benzoxazoles with enals has been conducted using density functional theory calculations. Our calculated results indicate that favored mechanism occurs through eight reaction steps: initial binding NHC to enals, followed by formation Breslow intermediate via proton transfer. Subsequent oxidation generates α,β-unsaturated acylazolium intermediate, which can undergo Michael addition benzoxazoles. Sequential protonation/deprotonation/cyclization produces six-membered cyclic undergoes catalyst elimination, leading final product. DABCO·H+ was found play important roles in transfer cyclization. Without DABCO·H+, energy barrier up 44.2 kcal/mol for step 2 is too high be accessible. With corresponding value lowered 18.6 kcal/mol. The cyclization 7.4 DABCO·H+. determines both regioselectivity. According NCI analysis, controlled strong interactions (such as C-H···O, C-H···N, π···π) between We also discuss solvent substituent effects role NHC. mechanistic insights obtained present would help improving current systems or designing new synthetic routes.

Language: Английский

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Visible-Light-Induced Regioselective Cascade Radical Cyclization of α-Bromocarbonyls: Access to Benzazepine Derivatives

The Journal of Organic Chemistry, Journal Year: 2024, Volume and Issue: 89(4), P. 2238 - 2246

Published: Jan. 31, 2024

Visible-light-induced regioselective cascade radical cyclization of α-bromocarbonyls for the synthesis benzazepine derivatives is described. In presence fac-Ir(ppy)3 (2.0 mol %) as a photocatalyst, 2,6-lutidine base, and dichloromethane solvent, reactions proceed smoothly to afford seven-membered rings in good yields. This protocol features broad substrate scope, excellent functional group tolerance, mild reaction conditions. Preliminary mechanistic studies reveal that generation α-carbon more prone react with 1,1-diphenylethylene tethered acrylamide generate stable heterocycle.

Language: Английский

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N-Heterocyclic Carbene Catalysis for Polycyclic Benzazepines Assembly: Regioselective Intramolecular Tandem Radical Cyclization

Organic Letters, Journal Year: 2024, Volume and Issue: 26(42), P. 9068 - 9072

Published: Oct. 11, 2024

A variety of polycyclic benzazepines were rapidly constructed by NHC-catalyzed regioselective redox-neutral intramolecular tandem cyclization. Initial mechanistic studies revealed that a SET radical process was possibly involved.

Language: Английский

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NHC-Catalyzed Tandem Reaction: A Strategy for the Synthesis of 2-Pyrrolidinone-Functionalized Phenanthridines

The Journal of Organic Chemistry, Journal Year: 2023, Volume and Issue: 88(23), P. 16556 - 16565

Published: Nov. 16, 2023

Herein, an N-heterocyclic carbene (NHC)-catalyzed tandem cyclization/addition/cyclization reaction of 2-isocyanobiaryls and α-bromo-N-cinnamylamides for the synthesis 2-pyrrolidinone-functionalized phenanthridines is developed. This protocol features a radical cascade process, broad substrate scope, good functional group compatibility under metal- oxidant-free conditions.

Language: Английский

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DFT investigation of the mechanism and role of N-heterocyclic carbene (NHC) in constructing asymmetric organosilanes using NHC-catalyzed [4+2] cycloaddition reaction

RSC Advances, Journal Year: 2024, Volume and Issue: 14(48), P. 35475 - 35489

Published: Jan. 1, 2024

The mechanism and origin of stereoselectivity for the synthesis asymmetric organosilanes using NHC are theoretically investigated.

Language: Английский

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Mechanism, Chemoselectivity, and Stereoselectivity of an NHC-Catalyzed Reaction of Aldehydes and Hydrazones: A DFT Study

The Journal of Physical Chemistry A, Journal Year: 2024, Volume and Issue: 128(22), P. 4483 - 4492

Published: May 24, 2024

To elucidate the mechanism and origins of chemo- enantioselectivities reaction between aliphatic aldehydes hydrazones catalyzed by triazolium-derived NHC, density functional theory computations have been performed. According to our calculated results, whole catalytic cycle for formation dihydropyridazinones proceeds via initial nucleophilic addition NHC an aldehyde, followed concerted intramolecular proton transfer C-Cl bond cleavage. Subsequent deprotonation generates enolate intermediate. The intermediate then undergoes 1,4-addition hydrazone construct a new carbon-carbon bond. following ring-closure would lead six-membered ring intermediate, which, upon release affords final product dihydropyridazinone. computation results reveal that is significantly promoted Brønsted acid DIPEA·H

Language: Английский

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Theoretical study of [3 + 3] annulation reaction of bromoenal with β-tetralone catalysed by N-heterocyclic carbene

Molecular Physics, Journal Year: 2024, Volume and Issue: unknown

Published: June 3, 2024

N-heterocyclic carbenes (NHCs) are effective organocatalysts, which widely used in various cycloaddition reactions. Among them, the [3 + 3] reaction type can be for synthesis of six-membered ring, is also one most important methods formation carbon–carbon bonds organic chemistry. In this paper, a possible pathway stereoselective bromoenal and β-tetralone have been investigated at M06-2X/6–31G(d,p)/IEFPCM(THF) level. Our suggested mechanism includes binding NHC to bromoenal, 1,2-proton transfer, debromination, 1,3-proton shift, Michael addition, protonation, deprotonation cyclisation, regeneration. The stereochemistry determined by addition step, favourable generates R-configurational dihydropyranone. Furthermore, through use global reactivity indexes (GRIs), we able demonstrate that nucleophilicity increased NHC. mechanistic insights gained work should helpful rational design potential catalysts analogous

Language: Английский

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Base-Promoted Ring Expansion Reaction of 4-Quinolones To Access Benzazepinones

Organic Letters, Journal Year: 2024, Volume and Issue: unknown

Published: Sept. 24, 2024

4-Quinolone derivatives undergo an unexpected ring expansion reaction with α-halo esters/phosphonates/sulfones in the presence of a base, such as NaH, to produce novel benzazepinones. Under these mild and transition-metal-free conditions, most substrates gave moderate excellent yields. The could be applied gram-scale synthesis drug-like molecules that greatly accelerated our structure-activity relationship studies. A plausible mechanism was proposed.

Language: Английский

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N-heterocyclic carbene switchable radical or benzyne meditated arylation of thiols using DMF/KOtBu

Synlett, Journal Year: 2024, Volume and Issue: unknown

Published: Nov. 4, 2024

Abstract A mild, metal, and photoredox-free direct arylation of alkyl aryl thiols with iodides using a DMF/KOt-Bu system has been developed. In the absence an N-heterocyclic carbene (NHC) additive, reaction proceeds via benzyne intermediate was suitable for substitution phenyl, while presence NHC or phenanthroline derivative improves regioselectivity substituted radical pathway. This protocol features inexpensive materials good substrate scope could be useful in thiols.

Language: Английский

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