Stereoselective Electrophilic
Cyclisation of <i>O</i>-Homoallyl Hydroxylamine Derivatives
作者:Armido Studer、Birgit Janza
DOI:10.1055/s-2002-34385
日期:——
isoxazolidines with moderate cis-selectivity (up to 7: 1). Electrophilic cyclisation of N-acylated O-homoallyl hydroxylamines provides isoxazolines or isoxazolidines depending on the reaction conditions (reagents). The t-BuOCl-mediated cyclisation affords isoxazolines via an oxidative cyclisation, whereas the NIS-induced reaction provides the 5-exo-cyclisation product with high stereoselectivity (cis:trans =
Stereoselective Cyclization Reactions of IBX-Generated Alkoxyamidyl Radicals
作者:Birgit Janza、Armido Studer
DOI:10.1021/jo0509399
日期:2005.8.1
[GRAPHICS]In this paper, a method for the generation of alkoxyamidyl radicals is presented. These N-centered radicals can efficiently be formed starting from the corresponding acylated alkoxyamines using IBX as an oxidant. Stereoselective 5-exo and 6-exo reactions with these N-heteroatom-centered radicals leading to isoxazolidines and [1,2]oxazinanes are discussed. The N-O bond in the heterocycles can readily be cleaved with SmI2 to provide N-acylated 1,3-amino alcohols.
Palladium-Catalyzed Ring-Forming Alkene Aminoaroylation of Unsaturated Hydrazones and Sulfonamides
The first example of a Pd(OAc)(2)-catalyzed ring-forming alkene aminoaroylation of unsaturated hydrazones and sulfonamides is described. This protocol features the use of diaryliodonium salts as both oxidants and aryl sources, thus enabling mild reaction conditions, good chemoselectivity, a broad substrate scope, and high functional group tolerance. A wide range of synthetically and biologically important functionalized dihydropyrazoles and isoxazolidines have been obtained in good yields.
Visible light-driven photocatalytic generation of sulfonamidyl radicals for alkene hydroamination of unsaturated sulfonamides
A visible light-driven photocatalytic generation of sulfonamidyl radicals, and application to intramolecular alkene hydroamination, has been accomplished.