Tandem Synthesis of 3-Halo-5-Substituted Isoxazoles from 1-Copper(I) Alkynes and Dihaloformaldoximes

Chen, Wenwen; Wang, Bo; Liu, Nan; Huang, Dayun; Wang, Xinyan

doi:10.1021/ol503008t

Cited by 35 publications

(11 citation statements)

References 59 publications

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“…More recently, Wang and Hu proposed copper(I)‐catalyzed cycloisomerization as a part of the mechanism in the synthesis of 3‐halo‐5‐substituted isoxazoles from copper acetylides and dihaloformaldoximes (not shown) 80…”

Section: Synthesis Of Isoxazoles Via Cycloisomerization Reactionsmentioning

confidence: 99%

β‐Cyclodextrin–Glycerol Dimers: Synthesis and NMR Conformational Analysis

Legros¹,

Vanhaverbeke²,

Souard³

et al. 2013

Eur J Org Chem

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The synthesis of new β‐cyclodextrin dimers linked through their primary faces by different glycerol‐like moieties by click chemistry is described. The unusual behaviour of these cyclodextrin–glycerol dimers in aqueous solution has been studied by NMR spectroscopy. We show that, depending on the length of the linking arm between the two cyclodextrins, the dimers could adopt very different conformations in water: symmetrical or pseudo[1]rotaxane‐like structures through one D‐glucopyranose unit tumbling in one β‐cyclodextrin.

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Section: Synthesis Of Isoxazoles Via Cycloisomerization Reactionsmentioning

confidence: 99%

β‐Cyclodextrin–Glycerol Dimers: Synthesis and NMR Conformational Analysis

Legros¹,

Vanhaverbeke²,

Souard³

et al. 2013

Eur J Org Chem

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“…As shown in Scheme , Fokin reported that the 1,3‐dipolar cycloaddition between a terminal alkyne 5 a and a nitrile oxide (in situ generated from α‐chloro‐oxime 49 ) can be improved significantly under CuAAC conditions. Unfortunately, no improvement was observed when dibromoformaldoximes 50 were used as substrates, because the bromonitrile oxide was generated too fast to be controlled in the presence of a base.…”

Section: Premade 1‐copper(i) Alkynes In Cycloadditionsmentioning

confidence: 99%

In‐situ Generated and Premade 1‐Copper(I) Alkynes in Cycloadditions

Wang

et al. 2017

The Chemical Record

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The copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) was discovered in 2002, which has become the most remarkable example for "click chemistry" to date. In CuAAC reaction, 1-copper(I) alkyne has been recognized to be a key intermediate. However, many contradictory experimental results for this intermediate were reported in literature. For example, only the in-situ generated 1-copper(I) alkyne was used, while the premade 1-copper(I) alkyne proved to be inefficient under the standard conditions. The kinetic studies indicated that CuAAC reaction had a strict second-order dependence on Cu(I) and the DFT studies demonstrated that 1-copper(I) alkyne intermediate should be a dinuclear copper(I) complex. But these results were inconsistent with the structure of the premade 1-copper(I) alkyne. Although hundreds of structurally different ligands were reported to significantly enhance the efficiency of CuAAC reaction, their functions were assigned to prevent the oxidation and the disproportionation of Cu(I) ion. Based on the investigation of the references and our works, we proposed that the in-situ generated 1-copper(I) alkyne in CuAAC reaction is not identical with the premade 1-copper(I) alkyne. The ligands may play dual roles to activate the 1-copper(I) alkyne by blocking the polymerization of the in-situ formed 1-copper(I) alkynes and dissociating the polymeric structures of the premade 1-copper(I) alkynes. As a result, we first disclosed that carboxylic acids can function as such activators and a novel carboxylic acid-catalyzed CuAAC strategy was developed, which has been proven to be the most convenient and highly efficient CuAAC method to date. Furthermore, highly efficient and regioselective methods for the syntheses of 1,4,5-trisubstituted 1,2,3-triazoles were developed by using the premade 1-copper(I) alkynes as substrates, in which the novel function of the premade 1-copper(I) alkynes as excellent dipolarophiles was first disclosed and applied. In this article, a series of works reported by our group for the in-situ generated and the premade 1-copper(I) alkynes in cycloadditions are reviewed.

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“…To avoid generating the hydrido-palladium species, we investigated an alternative Sonagashira coupling procedure. 16 In this protocol, Pd(PPh 3 ) 4 was used as catalyst, pre-synthesized copper(I) phenylethyne 17 as reactant, and…”

Section: Letter Syn Lettmentioning

confidence: 99%