Selective preparation of ( Z )- and ( E )-prop-1-enylamides from N -allylbenzamides

Ribereau, P.; Delamare, Madeleine; Célanire, Sylvain; Quéguiner, G.

doi:10.1016/s0040-4039(01)00467-1

Cited by 31 publications

(5 citation statements)

References 14 publications

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“…This rearrangement is followed by isomerization to the more stable benzylic carbanion that immediately reacts with the n ‐butyl bromide present in the reaction mixture. The ( Z )‐structure of the by‐product 3 can be visualized through an intermediate 7 , stabilized by Li/oxygen coordination . Searching for further insight into the proposed mechanism, the present work focuses on the study of the solvent effects.…”

Section: Resultsmentioning

confidence: 99%

“…The (Z)-structure of the by-product 3 can be visualized through an intermediate 7, stabilized by Li/oxygen coordination. [19] Searching for further insight into the proposed mechanism, the present work focuses on the study of the solvent effects. Because the reactions showed an unexpected diastereoselectivity the selection of the solvents was based on their coordination properties.…”

Section: Solvent Effectsmentioning

confidence: 99%

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Intramolecular carbolithiation‐cyclization‐electrophilic substitution: solvent effect and mechanistic study

Rodríguez

Nudelman

2013

J of Physical Organic Chem

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The intramolecular carbolithiation‐cyclization‐electrophilic substitution sequence proves to be a promising strategy for synthetic organic chemists. Our current research in this area focuses on the one‐pot halogen/lithium exchange of 2‐bromophenyl‐3‐phenylprop‐2‐enyl ether, followed by intramolecular carbolithiation, and trapping of the new lithiated cyclic intermediate by several electrophiles, affording 3‐substituted 2,3‐dihydrobenzofurans with some diastereoselectivity. Within this context, a study on the product distribution solvent dependence was carried out using different types of solvents, namely: polar coordinating, polar non‐coordinating, and non‐polar solvents. The results show that the coordinating features of the solvent affect specially the carbolithiation step, whereas the halogen/lithium exchange seems to be barely affected. Theoretical calculations were carried out to investigate the unexpected diastereoselectivity of the tandem reaction, where two stereocenters are generated. Insights gained from our mechanistic investigations enabled us to propose an inversion of configuration at the lithiated intermediate prior to the reaction, being the electrophile the likely cause for the observed distereoselectivity. Copyright © 2013 John Wiley & Sons, Ltd.

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Section: Resultsmentioning

confidence: 99%

Section: Solvent Effectsmentioning

confidence: 99%

Intramolecular carbolithiation‐cyclization‐electrophilic substitution: solvent effect and mechanistic study

Rodríguez

Nudelman

2013

J of Physical Organic Chem

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“…Classical procedures, such as the acylation of imines or the condensation of amides and carbonyl compounds require harsh reaction conditions and lead to the formation of considerable amounts of by‐products 7. An attractive alternative is the transition metal‐catalyzed8–11 or base‐mediated12 isomerization of readily available N ‐allylamides. Recently, Gooßen and co‐workers developed a stereoselective synthesis of enamides based on a ruthenium‐catalyzed direct addition of amides to terminal alkynes13–15.…”

Section: Methodsmentioning

confidence: 99%

Nickel‐Catalyzed Synthesis of Enamides and Enecarbamates via Isomerization of Allylamides and Allylcarbamates

et al. 2015

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As ingle-component, air-stable nickel precatalyst can catalyzet he isomerization of allylamides for the synthesis of enamides.T he scope of the reactione ncompassesv arious substituted allylamides anda llylcarbamates as well as homoallylamides.T he reactionc an be performed on am ultigram-scale without specialized glove-box equipment or Schlenk techniques.Keywords: enamides; enecarbamates; homogeneous catalysis;i somerization;nickel catalysis Enamidesa nd enecarbamates are very useful synthetic intermediates for various transformations,s uch as cycloadditions,c ross-coupling reactions or asymmetric C À Cb ond formations (Scheme1). [1][2][3][4] Furthermore,e namidesa nd enecarbamatesa re valuable substrates for asymmetric hydrogenation reactions. [3,4] Besides these applications,t he enamide motif is often found in natural products,f or example,a spergillamides [5] and salicylihalamides [6] . Due to importance of these classeso fc ompounds, several protocols for theirp reparation have been reported.[1-4] Classical procedures,s uch as the acylation of imines or the condensation of amides and carbonyl compounds require harsh reactionc onditions and lead to the formation of considerable amounts of byproducts.[7] An attractivea lternative is the transition metal-catalyzed [8][9][10][11] or base-mediated [12] isomerization of readily available N-allylamides.R ecently,G ooßen and co-workersd eveloped as tereoselective synthesis of enamides based on ar uthenium-catalyzed direct addition of amides to terminala lkynes [13][14][15] . Foro ne of our current research projects,w ew ere looking for an operationally simple,s calable and effiScheme 1. Synthesis and applicationso fe namides.

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“…Selective synthesis of E or Z N-vinyl ureas can be accomplished via deprotonation (Z) or Ru-catalyzed isomerization (E) of allyl ureas . Selective synthesis of E or Z prop-1-enylamides by base-catalyzed isomerization of N-allylbenzamides can be accomplished by allowing equilibration of the initially formed E intermediate . Base-catalyzed double bond migration in a variety of allyl ethers preferentially yields Z enol ethers, consistent with preferential stabilization of Z-1c . , Sodium diisopropyl amide in THF provides enhanced production of Z-2-pentene from 1-pentene under kinetic control, as well as synthetically useful >50:1 Z/E selectivity in allyloxy ether isomerization to enol ethers .…”

Section: Introductionmentioning

confidence: 97%

Attractive Nonbonded Interactions Help Stabilize the Z Form of Alkenyl Anions

Janesko

Villegas

2018

J. Org. Chem.

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Alkenyl anions (HC-CH═CH-Y; Y = aliphatic, aromatic, amine, ether) are often thermodynamically stable in the sterically congested Z form. This preference for Z structures is used to control regiochemistry in organometallic and Grignard reactions, allyl amine rearrangements to enamines, and allyl ether rearrangements to enol ethers. Explanations for Z stability in alkenes (Y = CHR) typically invoke through-space attraction (Coulomb or charge transfer) between the formally anionic carbon C1 and the Y = CHR hydrogens. However, this explanation is difficult to generalize to amines and ethers. We suggest that the orbital-driven so-called "attractive nonbonded interactions" suggested to stabilize the Z forms of 1,2-difluoroethylene and 1-substituted propenes also help stabilize Z alkenyl anions. We present electronic structure calculations and surveys of the experimental literature to show these effects' relevance for alkenyl anions. Our results suggest new approaches for regiocontrol in reactions with alkenyl anion intermediates and motivate revisiting older orbital-based theories of "attractive nonbonded interactions".

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Selective preparation of ( Z )- and ( E )-prop-1-enylamides from N -allylbenzamides

Cited by 31 publications

References 14 publications

Intramolecular carbolithiation‐cyclization‐electrophilic substitution: solvent effect and mechanistic study

Intramolecular carbolithiation‐cyclization‐electrophilic substitution: solvent effect and mechanistic study

Nickel‐Catalyzed Synthesis of Enamides and Enecarbamates via Isomerization of Allylamides and Allylcarbamates

Attractive Nonbonded Interactions Help Stabilize the Z Form of Alkenyl Anions

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