Application, Reactivity and Synthesis of Isoxazole Derivatives

Walunj, Yogesh

doi:10.2174/18756298mta25ntqfx

Cited by 2 publications

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“…To further extend the synthetic application of the products, isoxazole and pyrazole were synthesized with hydroxyl amine hydrochloride and phenylhydrazine in acidic conditions respectively (Scheme 2b & 2c). These heterocycles play a major role in the synthesis of pharmaceuticals, bioactive natural products, agricultural fields, materials, and catalysts [20b–e] . On the other hand, scalability is an important factor for the next stage of development in the process and herein, we tested using compound 1 a on a gram scale under the standard conditions.…”

Section: Resultsmentioning

confidence: 99%

Visible Light‐Promoted Fluorescein/Ni‐Catalyzed Synthesis of Bis‐(β‐Dicarbonyls) using Olefins as a Methylene Bridge Synthon

et al. 2022

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Herein, we report the synthesis of methylenebridged bis-1,3-dicarbonyls from olefins and 1,3-dicarbonyls using a photoredox/nickel-catalyzed synergistic approach. Styrene is reported as methylene one-carbon (C1) synthons in the synthesis of bis-(β-dicarbonyls) for the first time. The deuterated study showed the incorporation of styrene-d 3 in the product by NMR and Mass analysis. Fluorescence quenching and cyclic voltammetry (CV) suggest that the reaction proceeds via an energy transfer process (EnT). The key aspects of the protocol are the use of benign photocatalyst fluorescein, peroxide-free, air as oxidant, broader substrate scope, and 56% to 99% product yields. The synthetic application of the product has been extended to construct tetrasubstituted pyridines in a sequential one-pot manner, bis-isoxazole, and bis-pyrazole.

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Section: Resultsmentioning

confidence: 99%

Visible Light‐Promoted Fluorescein/Ni‐Catalyzed Synthesis of Bis‐(β‐Dicarbonyls) using Olefins as a Methylene Bridge Synthon

et al. 2022

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Mechanisms and Origins of Regio- and Stereoselectivities in NHC-Catalyzed [3 + 3] Annulation of α-Bromoenals and 5-Aminoisoxazoles: A DFT Study

Zhang,

2024

J. Org. Chem.

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Density functional theory (DFT) calculations were conducted to explore the mechanisms and origins of regio-and stereoselectivities underlying the [3 + 3] annulation reaction between α-bromoenals and 5-aminoisoxazoles with N-heterocyclic carbene (NHC) as the catalyst. The reaction occurs in nine steps:(1) nucleophilic addition of NHC to α-bromoenal, (2) Breslow intermediate formation through 1,2-proton transfer, (3) debromination, (4) α,β-unsaturated acyl azolium intermediate formation via 1,3-proton transfer, (5) addition of α,β-unsaturated acyl azolium intermediate to 5-aminoisoxazole, (6) deprotonation, (7) protonation, (8) ring closure, and (9) elimination of NHC. For the fifth step, 1,2-addition suggested in the experiment was not supported by our results. Instead, we found that Michael addition is energetically the most feasible pathway and the stereocontrolling step that preferentially provides the S-configuration product. DFT-computed results and experimental findings agree well. Analysis of distortion/interaction reveals that lower distortion energy leads to stability of the transition state corresponding to the Sconfiguration product. Global reactivity index analysis indicates that the behavior of the NHC catalyst differs significantly before and after the Breslow intermediate debromination. Before debromination, the nucleophilicity of α-bromoenal is enhanced by addition to NHC. However, after debromination, the α,β-unsaturated acyl azole generates and acts as an electrophilic reagent.

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Application, Reactivity and Synthesis of Isoxazole Derivatives

Cited by 2 publications

References 0 publications

Visible Light‐Promoted Fluorescein/Ni‐Catalyzed Synthesis of Bis‐(β‐Dicarbonyls) using Olefins as a Methylene Bridge Synthon

Visible Light‐Promoted Fluorescein/Ni‐Catalyzed Synthesis of Bis‐(β‐Dicarbonyls) using Olefins as a Methylene Bridge Synthon

Mechanisms and Origins of Regio- and Stereoselectivities in NHC-Catalyzed [3 + 3] Annulation of α-Bromoenals and 5-Aminoisoxazoles: A DFT Study

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