from substituted aldoximes (mixture of E and Z) and alkynes, using alkyl nitrites under conventional heating conditions. The key nitrile oxide intermediates that are required for the synthesis of isoxazoles are formed by treatment of substituted aldoxime with either tert-butyl nitrite or isoamyl nitrite. The generated nitrile oxides underwent in situ [3+2] dipolar cycloaddition to the substituted alkynes
Synthesis of isoxazoles by hypervalent iodine-induced cycloaddition of nitrile oxides to alkynes
作者:Anup M. Jawalekar、Erik Reubsaet、Floris P. J. T. Rutjes、Floris L. van Delft
DOI:10.1039/c0cc04646a
日期:——
Treatment of oximes with hypervalent iodine leads to substituted isoxazoles via rapid formation of nitrile oxides. Reaction with terminal alkynes led to a series of 3,5-disubstituted isoxazoles with complete regioselectivity and high yield, in a procedure mild enough to prepare a range of nucleoside and peptide conjugates. Exceptionally high reactionrates were found for the formation of 3,4,5-trisubstituted
A catalytic reaction comprises several steps: providing a catalyst, wherein the catalyst is metal or metal oxide particles and at least have 110} crystal plane; using the catalyst when performing a cycloaddition reaction. By using the catalyst with high reactivity, reaction rate is dramatically promoted.
Copper-catalysed synthesis of 3,5-disubstituted isoxazoles enabled by pyridinyl benzimidazol (PBI) as a bidentate N-chelating ligand under mild conditions
promote clean synthesis of 3,5-disubstituted isoxazoles in the presence of copper acetate as catalyst. This catalytic approach initiates with the hydroxyamination of aldehydes followed by chlorination and then generation of nitrile oxide which subsequently undergoes click-type [3 + 2]-dipolar cycloaddition with alkynes to give isoxazoles. This method provides an alternative green process to construct isoxazole
Efficient and convenient method for the synthesis of isoxazoles in ionic liquid
作者:Hassan Valizadeh、Mohammad Amiri、Hamid Gholipur
DOI:10.1002/jhet.20
日期:2009.1
An efficient one-pot synthesis of 3,5-disubstitueted isoxazoles from β-diketones in room temperature ionicliquids (ILs) is described. Compared with the classical reaction conditions, this new synthetic method is environmentally friendly and has the advantages of recyclability of IL and very good to excellent yields. J. Heterocyclic Chem., (2009).