Les Tribromures De Phosphoniums. Agents De Bromation De Substrats Organiques

Cristau, Henri‐Jean; Torreilles, E.; Morand, Philippe; Christol, Henri

doi:10.1080/03086648508072751

Cited by 11 publications

(8 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…After esterification, unsaturation was introduced by bromination, followed by base-catalysed elimination. [15] 3-Acetylacrylates 2a-b were directly brominated with the recyclable triphenylphosphonium perbromide [16] to afford the unsaturated bromo esters (E)-3a-b in about 50 % overall yield after chromatographic purification. Although both methyl and ethyl esters (3a) have already been reported, [17] the selective direct bromination of the 3-acetylacrylates 2a-b or related compounds proved unprecedented.…”

Section: Resultsmentioning

confidence: 99%

A New Approach to the Synthesis of N‐Alkylated 2‐Substituted Azetidin‐3‐ones

2006

View full text Add to dashboard Cite

We report a one-pot methodology for the synthesis of N-alkylated 2-substituted azetidin-3-ones based on a tandem nucleophilic substitution followed by intramolecular Michael reaction of primary amines with alkyl 5-bromo-4-oxopent-2-enoates, obtained in turn in three steps from levulinic acid. IntroductionSince the azetidin-3-one core has been used as a precursor for the synthesis of the natural sphingosine-type alkaloids penaresidines A and B and penazetidin A, [1] or as an intermediate in the synthesis of polyoxin antibiotics, [2,3] a number of different methodologies to obtain these fourmembered heterocycles have previously been described. [4] Cyclisation based on rhodium carbenoid intramolecular NH insertion has been developed by Seebach for the preparation of some azetidine-containing amino alcohol and amino acid derivatives [5] and by Vederas et al. for the synthesis of keto-glutamine analogues, [6] while De Kimpe has recently reported the synthesis of 4-alkyl-1-benzhydryl-2-(methoxymethyl)azetidin-3-ol as the result of stereoselective alkylation at the C-4 position of the corresponding azetidin-3-one obtained through a high-temperature reaction of an N-(diphenylmethylidene)-3-bromoamine precursor. [7] Azetidin-3-ones could also be obtained from the corresponding azetidin-3-ol precursors by use of pyridinium dichromate or Swern-type oxidation conditions. [8] As part of a recently started program aiming at the transformation of non-food/non-feed agricultural products, byproducts and waste materials into commodity chemicals we were interested in fine chemistry application of polyfunctionalised building blocks. One such derivative is 4-oxopentanoic acid or levulinic acid (LA; 1), traditionally obtained through the controlled degradation of hexose sugars by mineral acids.[9] The increasing number of patents directed towards the production of levulinic acid demonstrates its potential as an important basic chemical that could now be cost-efficiently produced from raw materials such as wood, [a] 2440A mechanistic interpretation of these reactions and an attempted enantioselective approach are also described. Germany, 2006) starch, cellulose-containing waste materials, recycled paper, or agricultural residues.[10]Beside its conversion into methyltetrahydrofuran, a fuel extender, or into δ-aminolevulinic acid, a biodegradable broad spectrum herbicide, [11] levulinic acid (1) also offers a great number of other synthetic transformations, [12] such as the synthesis of fused heterocycles prepared from norbornane amino acids and diamines [13] or the synthesis of the antibiotic lissoclinolide. [14] For a recent synthetic endeavour we needed ethyl 5-bromo-4-oxopent-2-enoate (3a) as key intermediate. This levulinic acid derivative appeared to be an even more versatile intermediate for further transformations such as Diels-Alder reactions, coupling reactions, nucleophilic substitutions and conjugate additions, and it was speculated that nucleophilic substitution combined with intramolecular Michael reaction should ope...

show abstract

Section: Resultsmentioning

confidence: 99%

A New Approach to the Synthesis of N‐Alkylated 2‐Substituted Azetidin‐3‐ones

2006

View full text Add to dashboard Cite

show abstract

“…The method is general and allows a broad range of substrates with good product yields. It may be noted that most of the α′,α′-dibromoketones synthesized have not been reported so far except for compound 4a . The advantage of this method lies in the fact that the bromination methods have been improved and enhanced through the mediation of selenium dioxide.…”

Section: Discussionmentioning

confidence: 99%

“…The few known synthetic routes of α,β-unsaturated α′-bromoketones and α,β-unsaturated α′,α′-dibromoketones are shown in Scheme . Earlier, Calo’ and co-workers reported the synthesis of α,β-unsaturated α′-bromoketones using 2,4,4,6-tetrabromocyclohexa-2,5-dienone (Scheme a), while Cristau et al reported that a mixture of α,β-unsaturated α′-bromoketones and α,β-unsaturated α′,α′-dibromoketones were obtained when α,β-unsaturated ketones were treated with tribromo triphenylmethylphosphonium (Scheme b) . In 1991, Mitami et al reported a regioselective α′-bromination of α,β-unsaturated ketones by an electrochemical procedure (Scheme c) .…”

Section: Introductionmentioning

confidence: 99%

Selenium Dioxide-Mediated Bromination of α,β-Unsaturated Ketones Using N-Bromosuccinimide in the Presence of p-Toluenesulfonic Acid: A Versatile Route for the Synthesis of α′-Bromo-4-arylbut-3-en-2-one and α′,α′-Dibromo-4-arylbut-3-en-2-one

et al. 2021

View full text Add to dashboard Cite

An efficient method for the synthesis of α,β-unsaturated α′-bromoketones and α,β-unsaturated α′,α′-dibromoketones is described using N-bromosuccinimide (NBS) as the brominating agent mediated by selenium dioxide (SeO2) in the presence of p-toluenesulfonic acid (PTSA) monohydrate in toluene. The method is simple, employing easily available shelf reagents to afford a wide range of products in good yields. The method highlighted that simple fine-tuning of the reaction conditions and molar equivalents of the reactants easily affords either mono- or dibrominated products in excellent yields. A number of these products have not been reported in the literature. All of the reactions were carried out in gram-scale quantities.

show abstract

“…These attributes make phosphonium salts attractive and interesting alternative halogenation reagents. There are many different cations and their counterions that can be used as oxidative 18 , reductive or brominating agents in polar and non-polar solvents 19 . Considering the diverse uses of these reagents, it becomes important to incorporate newer tribromides into the existing series.…”

Section: Introductionmentioning

confidence: 99%