Desulfonylation of Amides using Tributyltin Hydride, Samarium Diiodide or Zinc/Titanium Tetrachloride. A Comparison of Methods

Knowles, Haydn S; Parsons, Andrew F.; Pettifer, Robert M.; Rickling, Stéphane

doi:10.1016/s0040-4020(00)00025-9

Cited by 71 publications

(45 citation statements)

References 38 publications

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“…Benzylamine was used as nucleophile and 1b instead of 1a was used as substrate. Both 1 H NMR and 13 C NMR spectra of the product correspond to literature spectra of N-benzylbenzamide, [32][33][34] corroborating the view that nucleophilic substitution did indeed take place. Reaction between 1b and phenylamine in benzene was shown to yield N-phenylbenzamide.…”

Section: 31supporting

confidence: 76%

General‐base catalysed hydrolysis and nucleophilic substitution of activated amides in aqueous solutions

Buurma

Blandamer

Engberts

2003

J of Physical Organic Chem

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General-base catalysed hydrolysis and nucleophilic substitution of activated amides in aqueous solutions Buurma, NJ; Blandamer, MJ; Engberts, Jan; Buurma, Niklaas J. Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. ABSTRACT: The reactivity of 1-benzoyl-3-phenyl-1,2,4-triazole (1a) was studied in the presence of a range of weak bases in aqueous solution. A change in mechanism is observed from general-base catalysed hydrolysis to nucleophilic substitution and general-base catalysed nucleophilic substitution. A slight tendency is also observed for the more hydrophobic general bases to show higher reactivity towards 1a. Aspartame is an effective nucleophile, possibly because nucleophilic substitution is subject to intramolecular general-base catalysis. A general conclusion derived from the present results is that unexpected rate effects can only be rationalised provided that the detailed reaction mechanisms are well understood. Copyright  2003 John Wiley & Sons, Ltd.KEYWORDS: hydrolysis; changes in mechanism; general-base catalysis; general-acid catalysis; nucleophilic substitution INTRODUCTIONThe hydrolysis reaction of the activated amide 1-benzoyl-3-phenyl-1,2,4-triazole (1a) is general-base catalysed (Scheme 1). 1In highly aqueous solutions, the concentration of water is sufficiently high for water to act (detectably) as both a general base and a nucleophile. Hence, in the absence of other general bases, the water-catalysed (i.e. pHindependent) hydrolysis is the sole reaction. In the presence of sufficiently basic cosolutes, the watercatalysed reaction is unimportant. More basic cosolutes are much more effective catalysts for hydrolysis than water. Consequently, despite the relatively low molality of added general bases, the general-base catalysed hydrolysis pathway competes with the water-catalysed pathway. It is stressed that even though in the watercatalysed reaction the second water molecule in the activated complex (i.e. B = H 2 O, Scheme 1) acts as a general base, a distinction is drawn between the watercatalysed reaction and general-base catalysed reaction.Increased basicity of cosolutes usually leads to a concomitant increase in nucleophilicity. This increase in nucleophilicity provides an alternative reaction pathway: nucleophilic attack on the carbonyl functionality, followed by loss of the (substituted) 1,2,4-triazole leaving group (Scheme 2).In this mechanism, the nucleophilic water molecule is replaced by a stronge...

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Section: 31supporting

confidence: 76%

General‐base catalysed hydrolysis and nucleophilic substitution of activated amides in aqueous solutions

Buurma

Blandamer

Engberts

2003

J of Physical Organic Chem

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“…26 The knock on N-sulfonyl groups is that they are hard to remove by either hydrolysis or reduction. 27 Here the 2-halosulfonyl group functions as “self-oxidizing protecting group”; 28 it is removed under mild reductive conditions to give a valuable imine product that is oxidized on the carbon skeleton with respect to the precursor.…”

Section: Resultsmentioning

confidence: 99%

Radical Cyclizations of Cyclic Ene Sulfonamides Occur with β-Elimination of Sulfonyl Radicals to Form Polycyclic Imines

et al. 2013

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Radical cyclizations of cyclic ene sulfonamides provide stable bicyclic and tricyclic aldimines and ketimines in good yields. Depending on the structure of the precursor, the cyclizations occur to provide fused and spirocyclic imines with five-, six-, and seven-membered rings. The initial radical cyclization produces an α-sulfonamidoyl radical that undergoes elimination to form the imine and a phenylsulfonyl radical. In a related method, 3,4-dihydroquinolines can also be produced by radical translocation reactions of N-(2-iodophenylsulfonyl)tetrahydroisoquinolines. In either case, very stable sulfonamides are cleaved to form imines (rather than amines) under mild reductive conditions.

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“…[9c] The N-tosylindenamines prepared by using this method can be readily unprotected by treating them with SmI 2 . [13] Similarly, these N-tosylindenamines are easily converted into the corresponding indenones with tetrabutylammonium fluoride (Scheme 5). [14] …”

Section: Resultsmentioning

confidence: 99%

Ruthenium(II)‐Catalyzed CH Bond Activation: An Efficient Route toward Indenamines

2014

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An efficient and atom‐economical method for the synthesis of substituted indenamines from N‐tosylarylimines and alkynes via ruthenium(II)‐catalyzed CH bond activation and annulation is described. The catalytic reaction proceeds well with a broad substrate scope and in good yields. A possible mechanism is proposed that involves imine nitrogen chelation‐assisted ortho‐CH bond activation of the substrate, alkyne insertion, and intramolecular insertion of the CN Ts group into the CRu bond. Isotope‐labeling experiments are performed to understand the underlying mechanism of the reaction.

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Desulfonylation of Amides using Tributyltin Hydride, Samarium Diiodide or Zinc/Titanium Tetrachloride. A Comparison of Methods

Cited by 71 publications

References 38 publications

General‐base catalysed hydrolysis and nucleophilic substitution of activated amides in aqueous solutions

General‐base catalysed hydrolysis and nucleophilic substitution of activated amides in aqueous solutions

Radical Cyclizations of Cyclic Ene Sulfonamides Occur with β-Elimination of Sulfonyl Radicals to Form Polycyclic Imines

Ruthenium(II)‐Catalyzed CH Bond Activation: An Efficient Route toward Indenamines

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