The strategic use of <i>para</i>-quinone methides to access synthetically challenging and chemoselective α,α′-diarylmethyl <i>N</i>-glycosides from unprotected carbohydrate amines

Sangwan, Rekha; Dubey, Aditi; Tiwari, Ashwani Kumar; Mandal, Pintu Kumar

doi:10.1039/d0ob00039f

Cited by 8 publications

(3 citation statements)

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“…Very recently, enantioselective addition of oxazolin‐5‐ones to Michael acceptors 86 has been reported [194] . Moreover, Zn(OTf) 2 , [195] tropylium salt, [196] and Sc(TfO) 3 [197] are Lewis acid catalyst for the chemoselective 1,6‐addition of various N‐nucleophiles to para‐ quinones methides 86 . For example, reactions with carbamates proceed in the presence only 5 mol % of tropylium salt under mild conditions and target adducts 87 are obtained in good to quantitative yields [196] .…”

Section: The Problem Of Regio‐ and Chemoselectivitymentioning

confidence: 99%

Aza‐Michael Reaction: A Decade Later – Is the Research Over?

Rulev

2023

Eur J Org Chem

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The 1,4‐conjugated addition of nitrogen centered nucleophiles to electron‐deficient alkenes, historically called the aza‐Michael addition, is one of the most significant and widely used reactions in modern synthetic organic chemistry. In the last decade, great progress has been made in this field namely in the development of various catalytic systems. Fundamental advances involve the use of transition metal catalysts, organocatalysts, enzymes, ionic liquids, Brønsted and Lewis acids and bases. This Review aims to critically analyze the results of research into the reactions of aliphatic and aromatic amines with Michael acceptors.

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Section: The Problem Of Regio‐ and Chemoselectivitymentioning

confidence: 99%

Aza‐Michael Reaction: A Decade Later – Is the Research Over?

Rulev

2023

Eur J Org Chem

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“…Moving toward chemoselective functionalization of carbohydrate amines, another new strategy was developed by our research group, involves the strategic use of para ‐quinone methides first time for α,α'‐ N ‐diarylmethylation at any position of protected and unprotected sugar moiety (Scheme ) . Due to high reactivity and intrinsic electrophilic nature, para ‐quinone methides were used to access the synthetically challenge α,α'‐diarylmethylated N ‐glycosides derivatives 40 via Sc(OTf) 3 ‐catalyzed 1,6‐conjugate addition of protected and unprotected sugar amines 38 .…”

Section: General Strategy For the Chemical N‐functionalizationmentioning

confidence: 99%

An Overview on the ChemicalN‐Functionalization of Sugars and Formation ofN‐Glycosides

2020

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Its even more than a centennial that the systematic researches of chemical alteration of sugars have been advancing. Out of all the interest in the field of N‐glycoside has assembled pace over the past few years. Therefore, N‐functionalization of sugar is one of the most fundamental modifications along with other group like azide, amide etc also play a remarkable role in the field of glycoscience. Different approaches to access structurally modified N‐glycosides in carbohydrate derivatives are reviewed. The goal of this review is to provide an overview of different way of N‐functionalization of amino sugar and induction of nitrogen scaffolds for the synthesis of various orthogonal protective groups of the N‐glycoside. The N‐functionalization of sugars designate as follows: (a) glycosylamine, (b) glycosyl azide, and (c) introduction of N‐functionality to the sugar for formation of N‐glycosides. This is the first review focus on N‐functionalization of sugars which will be a future scope that influence the readers to work in this area further.

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“… , Numerous synthetic methods have been established to access α,α′-diarylmethyl amine or carbamate derivatives, including the arylation of imines, − the amination of diarylmethanols, − benzylic C–H amination via cross-dehydrogenative coupling, , the Lossen rearrangement of hydroxamic acids, , the reduction and transfer hydrogenation of imines, − the direct reductive amination of ketones, − the aryl migration of azides, desulfonylative amination, etc. A few other protocols have also been reported for the preparation of diarylmethyl amines from p -QMs through the base- or Lewis acid-mediated or catalyzed vinylogous conjugate addition of amines and amides. − …”

Section: Introductionmentioning

confidence: 99%

Tropylium Salt-Promoted Vinylogous Aza-Michael Addition of Carbamates to para-Quinone Methides: Elaboration to Diastereomerically Pure α,α′-Diarylmethyl Carbamates

et al. 2021

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Carbocation catalysis is emerging as an important subarea of Lewis acid catalysis. Some stable and isolable carbocations have been successfully utilized as Lewis acid catalysts and promoters in many synthetic transformations. In this manuscript, we report a tropylium cation-promoted vinylogous aza-Michael addition of carbamates to para-quinone methides (QMs) to access a wide range of unsymmetrical α,α′-diarylmethyl carbamates. This mild protocol was effective for the vinylogous conjugate addition of (−)-menthyl carbamate to p-QMs, and the respective diastereomerically pure α,α′-diarylmethyl carbamate derivatives could be obtained in excellent yields and diastereoselectivities (up to >20:1 de).

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The strategic use of para-quinone methides to access synthetically challenging and chemoselective α,α′-diarylmethyl N-glycosides from unprotected carbohydrate amines

Abstract: A practical route to access synthetically challenging and chemoselective α,α′-diarylmethyl N-glycosides via Sc(OTf)3-catalyzed 1,6-conjugate addition of unprotected amino sugars with p-QMs.

Cited by 8 publications

References 69 publications

Aza‐Michael Reaction: A Decade Later – Is the Research Over?

Aza‐Michael Reaction: A Decade Later – Is the Research Over?

An Overview on the ChemicalN‐Functionalization of Sugars and Formation ofN‐Glycosides

Tropylium Salt-Promoted Vinylogous Aza-Michael Addition of Carbamates to para-Quinone Methides: Elaboration to Diastereomerically Pure α,α′-Diarylmethyl Carbamates

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