Microwave‐Assisted Tandem Organocatalytic Peptide‐Coupling Intramolecular aza‐Michael Reaction: α,β‐Unsaturated <i>N</i>‐Acyl Pyrazoles as Michael Acceptors

Sánchez‐Roselló, María; Mulet, Cristina; Guerola, Marta; Pozo, Carlos del; Fustero, Santos

doi:10.1002/chem.201404596

Cited by 21 publications

(8 citation statements)

References 37 publications

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“…Another intramolecular aza‐Michael reaction of α,β‐unsaturated N ‐acyl pyrazoles 66 has been catalyzed by bifunctional squaramide C46 under MWI (Scheme ) . Products 67 were isolated in 70–98 % yield with 76 to 93 % ee .…”

Section: Organocatalysis Under Microwave and Ultrasonic Irradiationmentioning

confidence: 99%

Green Asymmetric Organocatalysis

et al. 2020

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Scheme12. At extile-supported organocatalyst for anhydride opening; MTBE = methyl tert-butyl ether.Scheme13. Organocatalytic aldolreaction conductedb yu sing the continuous-flow technique.Scheme11. PS-immobilized catalyst C32 for the amination of oxindoles 32.Scheme40. Photo-organocatalytic hydroxylation of ketoesters and amides. LED = light-emitting diode.Scheme41. Light-promoted cyclization.Scheme42. Light-promoted alkylation of aldehydes. EWG = electron-withdrawinggroup.Scheme49. Primary-aminec atalyzed light-promoted alkylations of dicarbonyl compounds.Scheme48. Light-promoted organocatalytic Michael additions.

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Section: Organocatalysis Under Microwave and Ultrasonic Irradiationmentioning

confidence: 99%

Green Asymmetric Organocatalysis

et al. 2020

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“…The scope of nucleophilic addition to electron-deficient double bonds (i.e., Michael addition) has been broadened by the development of asymmetric organocatalysis. − The analogous addition to conjugated alkynes is a potentially useful transformation, yielding a substituted vinylic system that can be further modified . Control of the alkene E / Z -stereochemistry is essential for such a reaction; however, stereoselective organocatalytic examples are relatively scarce.…”

Section: Introductionmentioning

confidence: 99%

Phosphazene Catalyzed Addition to Electron-Deficient Alkynes: The Importance of Nonlinear Allenyl Intermediates upon Stereoselectivity

Simón

Paton

2017

J. Org. Chem.

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An ONIOM(QM/MM) study on the mechanism of the Michael addition to triple bonds catalyzed by chiral diiminophosphorane catalysts has been performed to understand the stereoselectivity of the product olefin. Our results are consistent with the experimental enantioselectivity, but more importantly, reveal that the Z vs E preference depends on the influence of the catalyst upon the geometry of the allenyl enolate formed in the addition step. These intermediates show an innate preference for a (Z)-configuration, although this can be suppressed by steric interactions due to a catalyst. This leads to two distinct mechanisms in which the kinetic basis for (E) or (Z)-stereoselectivity is determined by a different step. Bifunctional iminophosphorane catalysts are found to use steric interactions to override innate stereoelectronic effects of the allenyl enolate reactive intermediate.

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“…Recently, the intramolecular variant of the aza-Michael reaction has been reported. 65 The (E)-1-(3,5-dimethyl-1H-pyrazol-1-yl)-7-(tosylamino)hept-2-en-1-one derivatives (3) have an NH group, whose acidity is increased by the tosyl substituent, suitable to give addition to the β-position of the α,β-unsaturated carbonyl moiety. The organocatalyst of choice is the squaramide incorporating cinchona alkaloid (S,S,R)-XXIVa (R′ = ethyl) that, in cylopentyl methyl ether (CPME) at 50−90°C, activates the approach to the β-Si face of the substrate to afford several derivatives with the (S)-1-(3,5-dimethyl-1H-pyrazol-1-yl)]-2-(1-tosylpiperidin-2-yl)-1-ethanone scaffold (S)-131.…”

Section: Aza-michael Reactionsmentioning

confidence: 99%