Expedient Organocatalytic Syntheses of 4-Substituted Pyrazolidines and Isoxazolidines.
Molecules
; 21(12)2016 Dec 01.
Article
em En
| MEDLINE
| ID: mdl-27916954
ABSTRACT
The efficient organocatalytic synthesis of heterocyclic systems of biological relevance is a subject of growing interest. We have found that the pyrrolidine/benzoic acid-catalyzed reaction of α-substituted propenals such as methacrolein, 2-benzylpropenal and 2-(n-hexyl)propenal with activated hydrazines takes place in very good yields (83%-99.6%) under very mild conditions to afford 4-substituted pyrazolidin-3-ols (as diastereomer mixtures); subsequent oxidation with PCC affords the corresponding-4-substituted-3-pyrazolidinones in essentially quantitative yields. In a similar way, 4-substituted isoxazolidinones are obtained with N-Cbz-hydroxylamine as a reagent. The use of chiral diarylprolinol trimethylsilyl ethers as catalysts allows the synthesis of several of these compounds in optically active form, in some cases with excellent enantioselectivity (up to 964 er). A preliminary evaluation of the biological activity shows that some of these compounds exhibit interesting antibacterial and antifungal activities.
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Base de dados:
MEDLINE
Assunto principal:
Oxazóis
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Pirazóis
Idioma:
En
Ano de publicação:
2016
Tipo de documento:
Article