Chemoselective Intermolecular Cross-Enolate-Type Coupling of Amides

Kaiser, Daniel; Teskey, Christopher J.; Adler, Pauline; Maulide, Nuno

doi:10.1021/jacs.7b08813

Cited by 92 publications

(48 citation statements)

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“…This term was introduced by D. Seebach and E. J. Corey to refer the inversion of reactivity of acyl carbon atoms in their reactions with electrophiles 2 . Analogous methods based on switching the reactivity of amines 3 , imines [4][5][6] , or carbonyl groups [7][8][9][10][11][12][13] have been developed in recent decades. This approach has played a pivotal role in the design of synthetic procedures, allowing access to target molecules that would be difficult to obtain by classical processes.…”

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confidence: 99%

An umpolung strategy to react catalytic enols with nucleophiles

et al. 2019

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The selective synthesis of α-functionalized ketones with two similar enolizable positions can be accomplished using allylic alcohols and iridium(III) catalysts. A formal 1,3-hydrogen shift on allylic alcohols generates catalytic iridium-enolates in a stereospecific manner, which are able to react with electrophiles to yield α-functionalized ketones as single constitutional isomers. However, the employment of nucleophiles to react with the nucleophilic catalytic enolates in this chemistry is still unknown. Herein, we report an umpolung strategy for the selective synthesis of α-alkoxy carbonyl compounds by the reaction of iridium enolates and alcohols promoted by an iodine(III) reagent. Moreover, the protocol also works in an intramolecular fashion to synthesize 3(2H)-furanones from γ-keto allylic alcohols. Experimental and computational investigations have been carried out, and mechanisms are proposed for both the inter-and intramolecular reactions, explaining the key role of the iodine(III) reagent in this umpolung approach.

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confidence: 99%

An umpolung strategy to react catalytic enols with nucleophiles

et al. 2019

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“…Alternatively, the keteniminium ion could be trapped with 2,6‐lutidine‐ N ‐oxides into XVI , then intramolecular attack of N‐ benzyl group occurred to afford 34 . Some anionic nucleophiles were found to be compatible with this reaction conditions . For example, sodium malonates as well as lithium enolates of ketones, esters and amides were found to give the corresponding adduct related to 35 in an intermolecular fashion.…”

Section: Intermolecular Addition Of Nucleophilesmentioning

confidence: 99%

Organocatalytic Oxidative Functionalizations of Alkynes

Patil

Shin

2018

Asian J Org Chem

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The catalytic oxidation of alkynes has traditionally belonged to the domain of transition metal catalysis. Recently, several promising organocatalytic methods have been developed, leading to selective oxidative transformations of alkynes. For example, ynamides, because of their electron-rich alkynes, are ideal candidates for Brønsted acid-catalysis. A closely related keteniminium intermediate could also be accessed via amide activation. A particularly interesting aspect in this regard is a facile access to umpolung enolates, which would enable novel disconnections with complementary selectivity to traditional methods. Scheme 1. Carbene reactivity: metal vs. Brønsted acid catalyst. Scheme 2. Routes for the generation of keteniminium ions. . Trapping vinyl cation with sulfoxide. Scheme 18. Iodine-Catalyzed oxidation of ynamides: a chemoselectivity change.

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“…In this respect, and using triflic anhydride-mediated amide activation (thereby obviating the presence of nucleophilic counteranions), the Maulide group has reported intra-and intermolecular nucleophile addition for C-C bond formation at the a-position of amides, enabling the formation of lactams (204) and 1,4dicarbonyls (205) (Scheme 28b). 114,115 A related elegant example was recently disclosed by the Miyata group, employing isoxazolidine amides (206) in combination with organoaluminium nucleophiles for the a-arylation of amides (Scheme 28c). 116 Moreover, chemoselective amide a-oxidation with N-oxides (employed for the transformation of linear amides) and TEMPO (preferred for branched and hindered amides) has been…”

Section: Review Articlementioning

confidence: 99%

Amide activation: an emerging tool for chemoselective synthesis

et al. 2018

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It is textbook knowledge that carboxamides benefit from increased stabilisation of the electrophilic carbonyl carbon when compared to other carbonyl and carboxyl derivatives. This results in a considerably reduced reactivity towards nucleophiles. Accordingly, a perception has been developed of amides as significantly less useful functional handles than their ester and acid chloride counterparts. However, a significant body of research on the selective activation of amides to achieve powerful transformations under mild conditions has emerged over the past decades. This review article aims at placing electrophilic amide activation in both a historical context and in that of natural product synthesis, highlighting the synthetic applications and the potential of this approach.

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Chemoselective Intermolecular Cross-Enolate-Type Coupling of Amides

Cited by 92 publications

References 48 publications

An umpolung strategy to react catalytic enols with nucleophiles

An umpolung strategy to react catalytic enols with nucleophiles

Organocatalytic Oxidative Functionalizations of Alkynes

Amide activation: an emerging tool for chemoselective synthesis

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