The asymmetric organocatalytic 1,3-dipolar cycloaddition of alkyl pyruvate-derived nitrones and α,β-unsaturated aldehydes

Weseliński, Łukasz J.; Kalinowska, Eleonora; Jurczak, Janusz

doi:10.1016/j.tetasy.2012.02.003

Cited by 11 publications

(10 citation statements)

References 38 publications

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“…In a preliminary study, the cycloadditions between C ‐carboxy ketonitrones 1b – 1g and 2A were conducted under uncatalyzed thermal conditions. As observed previously for 3aA ,[6b] the thermal 1,3‐DC reactions proceeded under microwave activation (Table ) to afford adducts in high yields as mixtures of three isomers ( 3 / 4 / 5 ), and the selectivity for the major exo isomer ( 3 ) ranged from 69 to 91 % (Table ).…”

Section: Resultssupporting

confidence: 59%

“…On the basis of these results, the organocatalytic asymmetric version of the 1,3‐DC between ketonitrones 1a – 1g and 2A was then investigated with chiral catalyst I (10 mol‐%) in dry nitromethane (Table , Figure )). [6b]…”

Section: Resultsmentioning

confidence: 99%

“…In 2012, the enantioselective 1,3‐DC reaction of ( E )‐crotonaldehyde with N ‐benzyl C ‐ethoxycarbonyl ketonitrone ( 1a ) catalyzed by the MacMillan organocatalyst I (Figure ) was reported , . Good yields (up to 75 %) were reached with high exo selectivities and enantioselectivities [up to 96:4 diastereomeric ratio ( dr ), 95 % ee ] under anhydrous conditions in nitromethane at –10 °C.…”

Section: Introductionmentioning

confidence: 99%

“…Good yields (up to 75 %) were reached with high exo selectivities and enantioselectivities [up to 96:4 diastereomeric ratio ( dr ), 95 % ee ] under anhydrous conditions in nitromethane at –10 °C. [6b] The obtained polyfunctional isoxazolidine 3aA possesses three contiguous stereogenic centers, including a quaternary one, and its absolute configuration was established. [6b] Such isoxazolidines have a high potential for synthetic applications, owing to the numerous modifications that can be envisaged, either involving the aldehyde functionality or through the chemodivergent N–O ring‐opening of the heterocycle.…”

Section: Introductionmentioning

confidence: 99%

“…[6b] The obtained polyfunctional isoxazolidine 3aA possesses three contiguous stereogenic centers, including a quaternary one, and its absolute configuration was established. [6b] Such isoxazolidines have a high potential for synthetic applications, owing to the numerous modifications that can be envisaged, either involving the aldehyde functionality or through the chemodivergent N–O ring‐opening of the heterocycle. For these reasons and on the basis of these preliminary and partial results, it seemed important to study the scope and limitations to obtain diverse quaternary‐containing 4‐formyl isoxazolidines and to investigate the mechanism of the organocatalytic process with consideration of all the experimental features.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Enantioselective 1,3‐Dipolar Cycloaddition Reactions of C‐Carboxy Ketonitrones and Enals with MacMillan Catalysts: Evidence of a Nonconcerted Mechanism

et al. 2017

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Highly diastereo‐ and enantioselective 1,3‐dipolar cycloadditions between functional ketonitrones and β‐substituted enals are promoted by MacMillan imidazolidinium organocatalysts. A study of the reaction scope shows that high selectivities are conserved if the N‐protecting group or the ester function is varied. However, the reaction is sensitive to steric interactions with the C substituent of the nitrone. In all cases, the reaction proceeds with high exo selectivity. In most cases, a third diastereomer, incompatible with a concerted mechanism, was also observed, albeit in minute amounts. DFT calculations suggest that the cycloaddition proceeds in a nonconcerted fashion by an initial oxa‐Michael‐type addition of the nitrone to the double bond followed by a cyclization. This mechanism explains the formation of the observed minor diastereomers. In addition, the diastereo‐ and enantioselectivities of the reaction were shown to be intermediately thermodynamically controlled, and the diastereomeric ratio is modulated by the kinetics of iminium hydrolysis.

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Section: Resultssupporting

confidence: 59%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Enantioselective 1,3‐Dipolar Cycloaddition Reactions of C‐Carboxy Ketonitrones and Enals with MacMillan Catalysts: Evidence of a Nonconcerted Mechanism

et al. 2017

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Regioselectivity Change in the Organocatalytic Enantioselective (3+2) Cycloaddition with Nitrones through Cooperative Hydrogen‐Bonding Catalysis/Iminium Activation

Prieto

Juste-Navarro

Uria

et al. 2017

Chemistry A European J

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The reaction of nitrones with enals through iminium activation can be modulated by using cooperative hydrogen‐bonding catalysis to induce the participation of a nitrone ylide (C‐N‐C) instead of the classical C‐N‐O dipole. As a consequence, N‐hydroxypyrrolidines are obtained, rather than the expected isoxazolidines. The reaction proceeds smoothly and high enantioselectivities are observed in all cases. By using the appropriate substrate, polysubstituted pyrrolidines incorporating quaternary stereocenters can be efficiently prepared.

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C−H Activation and Cross‐Coupling of Acyclic Aldonitrone

et al. 2021

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Palladium‐catalyzed activation of C(sp2)−H bond in a readily E,Z‐isomerizable aldonitrone, bearing an ester group at the C terminus, enabled its cross‐coupling with a variety of aryl and heteroaryl bromides to give ketonitrones, including products with functional groups not compatible with the classical nitrone synthesis via condensation with hydroxylamines. The reactions proceeded with very high (usually complete) E selectivity. The key to obtaining good yields of the cross‐coupling products was the use of sterically hindered carboxylic acid as additive and non‐polar solvent (toluene), in which the starting nitrone exists mainly as E isomer. Further use of the obtained ketonitrones in dipolar cycloaddition or nucleophilic addition has also been demonstrated.

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The asymmetric organocatalytic 1,3-dipolar cycloaddition of alkyl pyruvate-derived nitrones and α,β-unsaturated aldehydes

Cited by 11 publications

References 38 publications

Enantioselective 1,3‐Dipolar Cycloaddition Reactions of C‐Carboxy Ketonitrones and Enals with MacMillan Catalysts: Evidence of a Nonconcerted Mechanism

Enantioselective 1,3‐Dipolar Cycloaddition Reactions of C‐Carboxy Ketonitrones and Enals with MacMillan Catalysts: Evidence of a Nonconcerted Mechanism

Regioselectivity Change in the Organocatalytic Enantioselective (3+2) Cycloaddition with Nitrones through Cooperative Hydrogen‐Bonding Catalysis/Iminium Activation

C−H Activation and Cross‐Coupling of Acyclic Aldonitrone

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