title: Expedient Organocatalytic Syntheses of 4-Substituted Pyrazolidines and Isoxazolidines.
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 withN-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 96:4 er). A preliminary evaluation of the biological activity shows that some of these compounds exhibit interesting antibacterial and antifungal activities.
authors.affiliation: Division de Biotechnologie Industrielle, Centre National de Recherche en Biotechnologie, Ali Mendjli Nouvelle Ville, UV 03 BP E73, Constantine 25000, Algeria. t.yousfi@crbt.dz.|Laboratoire de Chimie Appliquée, Département de Chimie, Université 8 Mai 1945-Guelma, BP 401, Guelma 24000, Algeria. t.yousfi@crbt.dz.
authors.forename: Tarek
authors.initials: T
authors.lastname: Yousfi
authors.affiliation: Institute for Molecular Biosciences, The University of Queensland, St. Lucia QLD 4072, Australia. a.elliott@imb.uq.edu.au.
authors.forename: Alysha
authors.initials: A
authors.lastname: Elliott
authors.affiliation: Département de Génie de l'Environnement, Faculté de Génie des Procédés, Université de Constantine 3, Ali Mendjli Nouvelle Ville, BP72, Constantine 25000, Algeria. messiad_h@yahoo.fr.
authors.forename: Messiad
authors.initials: M
authors.lastname: Hanane
authors.affiliation: Laboratoire de Chimie Appliquée, Département de Chimie, Université 8 Mai 1945-Guelma, BP 401, Guelma 24000, Algeria. merdesra@yahoo.fr.
authors.forename: Rachid
authors.initials: R
authors.lastname: Merdes
authors.affiliation: Departament de Química Inorgànica i Orgànica, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, Barcelona 08028, Catalonia, Spain. amoyano@ub.edu.
authors.forename: Albert
authors.initials: A
authors.lastname: Moyano
mesh_terms: D002384:Catalysis; D010080:Oxazoles / Q000138:chemical synthesis* / Q000737:chemistry*; D011720:Pyrazoles / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D010080:Oxazoles; D011720:Pyrazoles
keywords: asymmetric catalysis; enals; hydrazines; hydroxylamines; isoxazolidinones; organocatalysis; pyrazolidinones