An asymmetric vinylogous Mukaiyama–Michael reaction of α,β-unsaturated 2-acyl imidazoles catalyzed by chiral Sc(<scp>iii</scp>)– or Er(<scp>iii</scp>)–pybox complexes

Rout, Subhrajit; Das, Arko; Singh, Vinod K.

doi:10.1039/c7cc01763d

Cited by 36 publications

(18 citation statements)

References 51 publications

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“…Preliminary work on this purpose was done by Doyle's group where the addition of enolates from 2‐diazo‐3‐butanoates 15 under Cu(II)‐box ligand catalysis afforded functionalized diazoacetoacetates 16 in good yields and enantioselectivities (Scheme a) . Following on this seminal report, γ‐butenolides 18 were prepared through the use of silyloxyfurans 17 as substrates under either Sc(III) or Er(III)‐indapybox catalysis (Scheme b) . Interestingly, by keeping the same chiral ligand, a simple switch in the metal‐center from Sc(III) to In(III) resulted in a complete reversal of the enantioselectivity.…”

Section: Classical Transition Metal Catalysis (M+l*)mentioning

confidence: 90%

“…[12] Following on this seminal report, γ-butenolides 18 were prepared through the use of silyloxyfurans 17 as substrates under either Sc(III) or Er(III)indapybox catalysis (Scheme 9b). [13] Interestingly, by keeping the same chiral ligand, a simple switch in the metal-center from Sc(III) to In(III) resulted in a complete reversal of the enantioselectivity. This could be observed during the synthesis of 1,5-diketones.…”

Section: Mukaiyama-michael Additionsmentioning

confidence: 99%

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Acyl‐Imidazoles: A Privileged Ester Surrogate for Enantioselective Synthesis

et al. 2019

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Since the first report by Evans in asymmetric Friedel-Crafts reactions, the use of acyl-imidazoles has blossomed as powerful ester/amide surrogates. The imidazole scaffold indeed displays stability and special activation features allowing both better reactivity and selectivity in traditional ester/amide functionalizations: α-(enolate chemistry), β-(conjugate additions), α,β-(cyclo-additions) or γ/δ-(vinylogous). An overview of the contemporary and growing interest in acyl-imidazoles in metal-and organo-catalyzed transformations (bio-hybrid catalytic systems will be fully described in a back-to-back Minireview) will be highlighted. Moreover, post-functionalization expediencies are also going to be discussed in this Minireview. Scheme 1. Synthesis of acyl-imidazoles by Okamoto and co-workers.Scheme 2. Synthesis of α,β-unsaturated acyl-imidazoles. . α-Alkylation of 2-naphthylmethyloxy acyl-imidazoles through PTC catalysis. NPM = 2-naphthylmethyl.Scheme 47. Chemo-and enantioselective oxidative cycloetherification of 2acyl-imidazoles with chiral quaternary ammonium salts. (please, change the chemdraw scheme 47; a new one is given) Scheme 48. Organocatalyzed enantioselective conjugate addition of aryl trifluoroborate to α,β-unsaturated 2-acyl 1-methylimidazole. 2 3 4 5 6 7 8

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Section: Classical Transition Metal Catalysis (M+l*)mentioning

confidence: 90%

Section: Mukaiyama-michael Additionsmentioning

confidence: 99%

Acyl‐Imidazoles: A Privileged Ester Surrogate for Enantioselective Synthesis

et al. 2019

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“…Very recently,S ingh et al reported the use of chiral Sc III /Er III -Pybox complexes,w hichc atalysed an asymmetricv inylogous Mukaiyama-Michael reaction of a,b-unsaturated 2-acyl imidazoles with silyloxyfurans (Scheme54). [61] The best resultsw ere obtained if 10 mol %S c(OTf) 3 -Pybox complexw as used as the catalysts ystem in CHCl 3 solvent, whereas in the case of erbium, the best results were obtained if aE r(OTf) 3 -Pybox complex was used at À20 8Cw ith 4 molecular sieves. a,b-Unsaturated 2-acyl imidazoles having EWGs/EDGs on the b-aryl ring reacted with silyloxyf uran 40 a to afford productsw ith high yield, diastereoselectivity and enantioselectivity.T he reaction proceeded smoothly with biaryl-, heteroaryl-and alkylsubstituted imidazoles.…”

Section: Mukaiyama Aldol Reactionmentioning

confidence: 99%

Applications of Pybox Complexes in Asymmetric Catalysis

et al. 2018

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Pybox ligands have found widespread application in organic synthesis and catalysis ever since their discovery, and their involvement in variousC ÀCa nd C-heteroatom bond-formingr eactions is rapidlyi ncreasing. In this Focus Review,w es ummarise the reactions involving various Pybox-metal combinations used for forming CÀCb onds, such as cross-coupling reactions, carbonyl-ener eactions, three-component reactions, allylation reactions, Diels-Alder reactions ando ther CÀCb ond-forming reactions. The literature from 2006to2 017 is covered.[a]

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“…Singh et al . introduced an asymmetric Michael addition protocol catalyzed by Sc‐pybox or Er‐pybox complex . Here the Mukaiyama dienolates (silyloxyfurans) on conjugate addition with α,β‐unsaturated 2‐acyl imidazoles lead to the stereoselective synthesis of γ‐butenolides (Scheme ).…”

Section: Sc‐pybox Complexmentioning

confidence: 99%

Recent Advances in the Creation of Asymmetric Carbon Centre(s) by Generation of Carbon‐Heteroatom Bond(s) Using Metal‐Pybox Complexes

Rohit¹,

Ujwaldev²,

Saranya³

et al. 2018

Asian J Org Chem

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Asymmetric synthesis is pivotal in modern-day organic synthesis in which metal-catalyzed protocols with compatible ligands play a key role. Many metal-chiral ligand combinations have been extensively reported in which "pybox" as the chiral ligand has occupied an indisputable place owing to its widespread use. This review focuses on the reactions of various metal-pybox combinations for the creation of asymmetric carbon centres by carbon-heteroatom bond manipulations. For brevity and simplicity, these reactions are classified based on the metal used and the literature from 2006-2018 is covered. Scheme 1. Stereoselective allylic oxidation of cyclic olefins using Cu-pybox catalyst. . Cu-Pybox catalyzed propargylic amination of propargylic acetates by aryl amines. lane was used in combination with L 18 (5 mol%) at low temperature (4°C).Use of various alkyl aryl ketones afforded the corresponding products with high ee value. For ketones with substituents at the meta-position of the aromatic ring, EWG's were found to result in higher yield than EDG's. In the case of parasubstituents, EWGs did not have much influence on the ee value. Again para-methoxyacetophenone was found to result in the formation of racemic alcohol. For ortho-substituents, the ee was found to reduce due to steric reasons. 2 3 4 5 6 7 8

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An asymmetric vinylogous Mukaiyama–Michael reaction of α,β-unsaturated 2-acyl imidazoles catalyzed by chiral Sc(iii)– or Er(iii)–pybox complexes

Cited by 36 publications

References 51 publications

Acyl‐Imidazoles: A Privileged Ester Surrogate for Enantioselective Synthesis

Acyl‐Imidazoles: A Privileged Ester Surrogate for Enantioselective Synthesis

Applications of Pybox Complexes in Asymmetric Catalysis

Recent Advances in the Creation of Asymmetric Carbon Centre(s) by Generation of Carbon‐Heteroatom Bond(s) Using Metal‐Pybox Complexes

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