Ni-catalyzed direct alcoholysis of N-acylpyrrole-type tertiary amides under mild conditions

Chen, Hang; Chen, Dong‐Huang; Huang, Pei‐Qiang

doi:10.1007/s11426-019-9665-5

Cited by 20 publications

(9 citation statements)

References 50 publications

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“…The residue was purified by silica gel column chromatography (eluent: n -hexane:EtOAc = 3:1 to 1:1) to give 2o as a colorless oil (1.28 g, 98% yield). Spectral data for 2o were consistent with those reported in ref .…”

Section: Methodssupporting

confidence: 88%

Amide-Ligand-Promoted Silver-Catalyzed C–H Fluorination via Radical/Polar Crossover

2023

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We describe an efficient method for benzylic C−H fluorination via sequential hydrogen-atom transfer (HAT) and oxidative radical-polar crossover utilizing the Ag(I)/Selectfluor system. Amide ligands, such as benzamide and sulfonamide, substantially facilitate the processes leading to a carbocation intermediate, which subsequently reacts with nucleophilic fluorinating reagent to form a C−F bond. This protocol is applicable to the fluorination of all 1°, 2°, and 3°C−H bonds as well as to late-stage C−H fluorination of bioactive molecules.T he introduction of a C−F bond into organic molecules alters their physical, chemical, and biological properties, and consequently, fluorine-containing compounds are of interest in many research fields. 1 However, few fluorinecontaining compounds are found in nature, 2 and therefore, artificial construction of the C−F bond is required. Tremendous effort has been devoted to the development of C−F bond-forming reactions 3 by many research groups including ours, 4 but there is still a need for methods to form C−F bonds under mild conditions, which would be suitable for late-stage modification.An oxidation system using Ag(I) and Selectfluor (1) is one of the most powerful tools for the construction of the C−F bond under very mild conditions. 5 In this system, Ag(I) is considered to be oxidized by 1 to produce high-valent silver species, such as Ag(II) or Ag(III), acting as a strong singleelectron oxidant. The oxidation of Ag(I) is operationally simple, occurring even at room temperature, and various radical fluorinations using the Ag(I)/Selectfluor system have been developed (Scheme 1A). For example, Li and co-workers reported efficient methods for decarboxylative fluorination 5a and deboronofluorination. 5c These reactions begin with singleelectron transfer (SET) between high-valent silver species and appropriate functional groups to afford an alkyl radical, followed by fluorine-atom transfer (FAT) from 1 to give the corresponding product. Although these methods can form the C−F bond in a site-specific fashion, preinstallation of certain functional groups in the starting material is required. Given that most biologically active compounds possess an abundance of C(sp 3 )−H bonds, direct and regioselective C(sp 3 )−H fluorination would be an attractive option for rapid fluoro derivatization. In this context, Baxter and co-workers developed benzylic C−H fluorination with the Ag(I)/ Selectfluor system, 5f,h in which the diazabicyclo radical cation 1′ generated from 1 is considered to serve as a hydrogen-atom transfer (HAT) reagent. Then, FAT from 1 to the resulting alkyl radical leads to the fluorinated product (Scheme 1B). However, this reaction is not applicable to 3°C−H

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Section: Methodssupporting

confidence: 88%

Amide-Ligand-Promoted Silver-Catalyzed C–H Fluorination via Radical/Polar Crossover

2023

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“…设计本反应的初衷是要得到 Michael 加成反应产物, 在 MgBu 2 存在下, 3,5-二甲基-N-α,β-不饱和酰基吡唑与丙酮氰醇反应得到了 Michael 加成产物, 产物的选择性为 100% (Entries 1 ～ 4). 但有趣的是 , 当以 TMG, n-BuLi, 2,2,6,6-四甲基哌啶 (TEMP) 和四甲基乙二胺 (TMEDA)等有机碱作催化剂时, 反应主要是丙酮氰醇丙酮氰醇酯是一种医药化工中间体, 已有文献报道其合成方法 [19][20][21]…”

Section: 结果与讨论unclassified

Study on the Reaction of Acetone Cyanohydrin with 3,5-Dimethyl-N-α,β-unsaturated Acyl Pyrazole

Fang¹,

You²,

Yu³

et al. 2020

Chin. J. Org. Chem.

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Cyano compounds are a class of organic compounds with great value. Two different kinds of reactions have been reported using acetone cyanohydrin as reagent and substituted 3,5-dimethyl-N-α,β-unsaturated acyl pyrazole as substrate. The reaction pathway depends on the basic catalysts used when aromatic substituted 3,5-dimethyl-N-α,β-unsaturated acyl pyrazole was used as the substrate. Michael addition reaction occurred in the presence of MgBu 2 with the product yield up to 95%, while alcoholysis reaction of amide occurred in the presence of 1,1,3,3-tetramethylguanidine (TMG), producing β-substituted phenyl cyanoacrylates with 84% yield. However, fatty substituted 3, 5-dimethyl-N-α,β-unsaturated acyl pyrazole and acetone cyanohydrin underwent Michael addition reaction in the presence of MgBu 2 or TMG, the product yield was up to 99%. The possible reaction mechanism when using different basic catalysts was discussed.

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“…Since Kashima applied pyrazoleamide derivatives to asymmetric synthesis field in 1996, pyrazoleamides and their derivatives have attracted the attention of more organic scientists because they are stable, easy to prepare, and easily converted into other compounds . In particular, α,β-unsaturated pyrazoleamides, as a class of excellent Michael receptor, have been widely used in asymmetric synthesis, since the pyrazolyl moiety not only greatly improves electrophilic activity of β-position but also matches well with chiral organocatalysts and chiral metal complexes .…”

Section: Introductionmentioning

confidence: 99%

Asymmetric Formal (3 + 2) Cyclocondensation of Coumarin-3-Formylpyrazoles as 3-Carbon Partners with 3-Hydroxyoxindoles via Esterification/Michael Addition Sequence

et al. 2022

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The first enantioselective formal (3 + 2) cyclocondensation involving α,β-unsaturated pyrazoleamides as 3-carbon partners was accomplished in a stepwise fashion. The stepwise esterification/Michael addition sequence is promoted by Zn(OTf) 2 and quinine-squaramide derivative, respectively. The protocol enables access to spiro-fused pentacyclic spirooxindoles from coumarin-3-formylpyrazoles and 3-hydroxyoxindoles in good to satisfactory overall yields (up to 91%) with excellent dr (all cases >20:1 dr) and high ee values (up to 99%). Mechanistic investigations contributed to shedding light on the enantioselective event of the process.

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Ni-catalyzed direct alcoholysis of N-acylpyrrole-type tertiary amides under mild conditions

Cited by 20 publications

References 50 publications

Amide-Ligand-Promoted Silver-Catalyzed C–H Fluorination via Radical/Polar Crossover

Amide-Ligand-Promoted Silver-Catalyzed C–H Fluorination via Radical/Polar Crossover

Study on the Reaction of Acetone Cyanohydrin with 3,5-Dimethyl-N-α,β-unsaturated Acyl Pyrazole

Asymmetric Formal (3 + 2) Cyclocondensation of Coumarin-3-Formylpyrazoles as 3-Carbon Partners with 3-Hydroxyoxindoles via Esterification/Michael Addition Sequence

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