Reactions of α, α-disubstituted selenoamides with organolithium reagents leading to unsymmetrical ketones

Murai, Toshiaki; Ezaka, Tatsuya; Katō, Shinzi

doi:10.1016/s0040-4039(98)00764-3

Cited by 15 publications

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“…Considerable attention has been paid to the chemistry of organoselenium compounds because of their value as synthetic reagents and their possible biological application . In the course of our studies on selenocarbonyl compounds, we previously reported efficient methods for the synthesis of aliphatic selenoamides and the conversion of α,α-disubstituted selenoamides with organolithium reagents to asymmetrical ketones . We further found that the reaction of selenoamides with lithium acetylide derived from (trimethylsilyl)acetylene and methyl iodide gives β-methylselenenyl α,β-unsaturated ketones .…”

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confidence: 96%

“…In the course of our studies on selenocarbonyl compounds, we previously reported efficient methods for the synthesis of aliphatic selenoamides and the conversion of α,α-disubstituted selenoamides with organolithium reagents to asymmetrical ketones . We further found that the reaction of selenoamides with lithium acetylide derived from (trimethylsilyl)acetylene and methyl iodide gives β-methylselenenyl α,β-unsaturated ketones . However, only a limited number of lithium acetylides and selenoamides were suitable for this transformation.…”

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confidence: 99%

“…Initially, the aromatic selenoamide 1a 6 was reacted with lithium acetylide 2a derived from (trimethylsilyl)acetylene at 0 °C to room temperature for 1.5 h, and then methyl iodide was added to the reaction mixture as described previously ).…”

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confidence: 99%

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MeOTf-Mediated Alkynylation of Selenoamides Leading to β-Methylselenenyl α,β-Unsaturated Ketones and Their Characterization

2001

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[reaction: see text] beta-Methylselenenyl alpha,beta-unsaturated ketones were effectively synthesized by treating selenoamides with methyl triflate, followed by reaction with lithium acetylides. The reaction proceeded with high stereoselectivity to give exclusively Z-isomers. (77)Se NMR studies and X-ray molecular structure analysis of beta-methylselenenyl alpha,beta-unsaturated ketones suggested that the products show 1,5-nonbonding interaction between the selenium atom and carbonyl oxygen atom.

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MeOTf-Mediated Alkynylation of Selenoamides Leading to β-Methylselenenyl α,β-Unsaturated Ketones and Their Characterization

2001

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“…Thus, thioamides 269 can react with organolithiums to yield ketones 258 upon acidic work‐up, in analogy to simple amides (see Section 2 and Scheme ). An analogous addition protocol is also known for selenoamides 140. Interestingly, the procedure can involve the in situ reduction of the addition intermediates to α‐disubstituted amines 271 141…”

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confidence: 99%

Increasing the Reactivity of Amides towards Organometallic Reagents: An Overview

2014

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The nucleophilic addition of carbon nucleophiles to amides has traditionally been a difficult task, both due to reactivity and selectivity problems. When successful, these processes would represent straightforward routes towards carbonyl‐type or amine compounds, depending on the fate of the generated tetrahedral intermediate. The direct addition of nucleophiles to amides for the preparation of ketones has been studied and applied to the syntheses of several natural products. On the other hand, the addition of nucleophiles to amides to obtain substituted amines represented a major challenge, and only scattered applications on particular substrates have appeared. Initial improvements were based on the activation of amides by introduction of particular substituents, such as in N‐methoxy amides (Weinreb amides) or electron‐withdrawing groups able to increase the carbon nucleophilicity. Although these strategies facilitate the introduction of nucleophiles, chemoselectivity issues arise when additional electrophilic moieties (i.e., carbonyls) are present, thus decreasing the versatility of the methods. In recent years, important advancements towards fully chemoselective methods have been realized. The capture of tetrahedral intermediates with acids generates highly electrophilic iminium species able to undergo chemoselective additions of various nucleophiles, thus accessing substituted amines. Alternatively, the in situ generation of an iminium triflate ion allows highly chemoselective additions of nucleophiles, yielding amines, ketones or ketimines. Also thioamides can be used as precursors of ketones or α‐substituted amines. The success of the above methodologies is further showcased by the application in various syntheses of natural products or biologically active molecules.

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“…The relative reactivity of alkoxycarbonyl and selenocarbamoyl groups toward methyllithium was tested (Scheme ) since both functional groups are known to be active toward organolithium compounds. , The treatment of δ-oxo selenoamide 4c with 2 equiv of methyllithium gave quantitatively δ-hydroxy selenoamide 5 . The methyllithium selectively added to the ethoxycarbonyl group, and the selenocarbamoyl group remained intact.…”

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Michael Addition of Selenoamides to α,β-Unsaturated Carbonyl Compounds: Stereocontrolled Synthesis of δ-Oxo Selenoamides and Their Reactivity

et al. 2000

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Reactions of α, α-disubstituted selenoamides with organolithium reagents leading to unsymmetrical ketones

Cited by 15 publications

References 13 publications

MeOTf-Mediated Alkynylation of Selenoamides Leading to β-Methylselenenyl α,β-Unsaturated Ketones and Their Characterization

MeOTf-Mediated Alkynylation of Selenoamides Leading to β-Methylselenenyl α,β-Unsaturated Ketones and Their Characterization

Increasing the Reactivity of Amides towards Organometallic Reagents: An Overview

Michael Addition of Selenoamides to α,β-Unsaturated Carbonyl Compounds: Stereocontrolled Synthesis of δ-Oxo Selenoamides and Their Reactivity

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