Reductive N–O cleavage of Weinreb amides by sodium in alumina and silica gels: synthetic and mechanistic studies

Jackson, James E.; O’Brien, Brittany N.; Kedzior, Sonya K.; Fryz, Gage R.; Jalloh, Fatmata S.; Banisafar, Arash; Caldwell, Michael; Braun, M.; Dunyak, Bryan M.; Dye, James

doi:10.1016/j.tetlet.2015.09.099

Cited by 12 publications

(7 citation statements)

References 25 publications

(18 reference statements)

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“…The N-O bond has low bond dissociation energy, with about 59 kcal mol −1 for hydroxylamines and 45 kcal mol −1 for oximes. 95 Cleavage of weak N-O bonds has been reported to be effective with Zn/H + , 12,14 zinc-copper couples in acetic acid, 96 sodium in liquid ammonia 96 or in alumina and silica gels, 97 H 2 /Pd/C, 98,99 105,106 or with RANEY® nickel/AlCl 3 in aqueous methanol. 107 However, resistance of phthaloyl or carbamate protected hydroxylamines to hydrogenolysis (catalysed by Pd/C) was also observed.…”

Section: Chemical and Physicochemical Properties Of Hydroxylaminesmentioning

confidence: 99%

N–O linkage in carbohydrates and glycoconjugates

Chen

Xie

2016

Org. Biomol. Chem.

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The importance of oligosaccharides and their conjugates in various biological and pathological processes has stimulated growing interest in the development of (neo)glycoconjugates. Thanks to its high nucleophilicity, hydroxylamine has been employed as a powerful chemoselective ligation tool. Great effort has been focused on carbohydrates bearing aminooxy or N-hydroxy amino groups for organic synthesis, glycobiology and drug discovery. This review provides an overview of N-O linked carbohydrates and glycoconjugates, focusing particularly on the synthetic methodologies and chemical and physicochemical properties as well as biological and medical applications of N-glycosyl and O-glycosyl hydroxylamines, N-hydroxy amino and O-amino sugar as well as sugar aminooxy acid derivatives.

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Section: Chemical and Physicochemical Properties Of Hydroxylaminesmentioning

confidence: 99%

N–O linkage in carbohydrates and glycoconjugates

Chen

Xie

2016

Org. Biomol. Chem.

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“…This is noteworthy given the difficulties associated with selective monoalkylation of primary amides and the attractiveness of reductive deprotection. The current suite of methods includes base-mediated elimination approaches and metal-reducing agents that enable single-electron-transfer (SET) processes: examples of the latter include samarium diiodide (N–OBn), lithium (DTBB/NH 3 ), sodium, ruthenium (Zn–Cu), and titanium reagents (Figure C). A metal-free alternative has also been demonstrated using a super electron donor . Although metal-based SET methods constitute the vanguard of N–O bond cleavage platforms, this dominance must be reconciled with limited functional group compatibility and operational challenges.…”

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confidence: 99%

Organophotocatalytic N–O Bond Cleavage of Weinreb Amides: Mechanism-Guided Evolution of a PET to ConPET Platform

et al. 2022

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A mild, organophotocatalytic N–O bond cleavage of Weinreb amides is disclosed, thereby expanding the chemistry of this venerable motif beyond acylation. This redox neutral process begins to reconcile the ubiquity of N–O bonds in contemporary synthesis with the disproportionately harsh, stoichiometric conditions that are often required for bond cleavage. The strategy is compatible with the parent alkyl derivatives (N–OMe, N–OAlkyl), thereby complementing tailored O-substituent approaches that require N–OAr groups (Ar = electron-deficient). A broad range of acyclic and cyclic derivatives are disclosed (>40 examples, up to 95%), and the synthetic utility of the method is demonstrated in a range of applications. In the case of cyclic Weinreb amide derivatives, this platform enables ambiphilic amide aldehydes, of varying chain lengths, to be generated in a single transformation. Inspired by Emil Fischer’s seminal 1908 synthesis of aminoacetaldehyde using sodium amalgam, this method provides a milder route to access this important class of materials. Mechanistically guided reaction development demonstrates the involvement of a photoinduced electron transfer (PET) mechanism, and this has been further advanced to a consecutive photoinduced electron transfer (ConPET) manifold: this has significantly expanded the scope of compatible substrates.

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“…Weinreb amides reacted with Na-SG (and also with Na supported on alumina gel) in THF at room temperature to afford the corresponding primary amides in moderate to high yields (Scheme 13). 30…”

Section: Further Applicationsmentioning

confidence: 99%

Silica Gel Stabilized Na and Na/K Alloys: Highly Effective, Versatile and Environmentally Friendly Reducing Agents

2017

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Na and Na/K alloys in the liquid phase can be absorbed into amorphous silica gel at loadings up to 40 wt%. Further heating of these so-called stage 0 materials at 150 or 400 °C furnishes stage I and stage II materials, respectively, as free-flowing powders that can be handled under much safer conditions than the corresponding starting materials. Stage I Na and Na 2 K possess valuable reducing properties and they have found a variety of low impact applications in organic synthesis, including, e.g., the reductive deprotection of several functional groups, the development of safer protocols to operate the Bouveault-Blanc and the Birch reductions, and a new and particularly efficient approach to the Grignard and Darzens reactions. 1 Introduction 2 Reductive Deprotection Procedures 3 Bouveault-Blanc Reduction of Esters 4 Ammonia-Free Birch Reductions 5 Synthesis of Alkyldiaryl-and Dialkylarylphosphines 6 CC Bond Forming Reactions 7 Further Applications 8 Conclusion

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Reductive N–O cleavage of Weinreb amides by sodium in alumina and silica gels: synthetic and mechanistic studies

Cited by 12 publications

References 25 publications

N–O linkage in carbohydrates and glycoconjugates

N–O linkage in carbohydrates and glycoconjugates

Organophotocatalytic N–O Bond Cleavage of Weinreb Amides: Mechanism-Guided Evolution of a PET to ConPET Platform

Silica Gel Stabilized Na and Na/K Alloys: Highly Effective, Versatile and Environmentally Friendly Reducing Agents

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