A general synthesis of bridged isoxazolidines from a double hetero-Michael addition of N-substituted hydroxylamines to quinone monoketals has been developed. The different addition order of N-benzylhydroxylamine and N-Boc hydroxylamine is also discussed. Moreover, the various functionalities in the isoxazolidine products allow facile derivatization.
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http://dx.doi.org/10.1021/ol401235z | DOI Listing |
Chem Commun (Camb)
August 2020
Department of Chemistry, Indian Institute of Technology Madras, Chennai-600036, Tamil Nadu, India.
A copper catalyzed three-component synthesis of π-conjugated tetracyclic thiochromeno-quinolinone and thiochromeno-thioflavone was established via oxidative double hetero Michael addition using in situ generated nucleophiles. Xanthate plays a dual role as an odourless sulfur source and a chemoselective reducing agent. The in situ formed iodine plays a crucial role in the oxidation step.
View Article and Find Full Text PDFOrg Lett
April 2016
Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States.
An efficient synthesis of the C22-C40 domain of the azaspiracids is described. The synthetic route features a Nozaki-Hiyama-Kishi (NHK) coupling and chelation controlled Mukaiyama aldol reaction to access an acyclic intermediate and a double-intramolecular-hetero-Michael addition (DIHMA) to provide the FG-ring system bridged ketal.
View Article and Find Full Text PDFOrg Lett
July 2013
Department of Chemistry, Hunter College, 695 Park Avenue, New York, New York 10065, USA.
A general synthesis of bridged isoxazolidines from a double hetero-Michael addition of N-substituted hydroxylamines to quinone monoketals has been developed. The different addition order of N-benzylhydroxylamine and N-Boc hydroxylamine is also discussed. Moreover, the various functionalities in the isoxazolidine products allow facile derivatization.
View Article and Find Full Text PDFOrg Biomol Chem
October 2012
Organic and Biomolecular Chemistry Division, Hyderabad-500 007, India.
The first total synthesis of dinemasone A, a bioactive metabolite with a spiroketal moiety, is described. The main strategy for the construction of the spiroketal unit involves a double intramolecular hetero-Michael addition (DIHMA) of an ynone moiety. The thus obtained axial-equatorial mono anomeric spiroketal, on spiroepimerization with ZnBr(2), was converted into the requisite axial-axial double anomeric spiroketal.
View Article and Find Full Text PDFOrg Biomol Chem
October 2010
Laboratory of Organic Chemistry, Department of Chemistry, Aalto University, School of Science and Technology, PO Box 16100, Kemistintie 1, FI-00076, Aalto, Finland.
An asymmetric synthesis of the C(9)-C(25) spiroketal fragment of calyculin C is described. Key steps include two crotylation reactions using successively Brown's reagent and (Z)-crotyltrifluorosilane for the formation of the anti, anti, anti stereotetrad, ynone formation by a Pd-catalyzed coupling of a thiol ester with a terminal alkyne and a double intramolecular hetero-Michael addition for the stereoselective construction of the spiroketal framework.
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