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Atom Donor (atom + donor)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

ChemInform Abstract: Complexes of Borane and N-Heterocyclic Carbenes: A New Class of Radical Hydrogen Atom Donor.

CHEMINFORM, Issue 49 2008
Shau-Hua Ueng
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Corrigendum: Borane,Lewis Base Complexes as Homolytic Hydrogen Atom Donors

CHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2010
Johnny Hioe
No abstract is available for this article. [source]

A Radical Version of the Bromo- and the Iodocyclization of Bis(homoallylic) Alcohols , The Synthesis of Halogenated Tetrahydrofurans by Stereoselective Alkoxyl Radical Ring Closures

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2003
Jens Hartung
Abstract A new synthesis of bromo- and iodomethyl-substituted tetrahydrofurans has been devised. The sequence starts with the conversion of aryl-functionalized bis(homoallylic) alcohols 1 into N -alkenoxythiazole-2(3H)-thiones 6 or pyridine-2(1H)-thiones 7. When photolyzed in the presence of appropriate trapping reagents, thiones 6 and 7 efficiently liberated substituted 4-penten-1-oxyl radicals 2, which underwent synthetically useful 5- exo -trig cyclizations. Cyclized radicals 3 were trapped with BrCCl3 or an adequate iodine atom donor (either n -C4F9I or diethyl 2-iodo-2-methyl malonate) to provide halocyclization products 4 or 5. This strategy has been applied for the synthesis of 3-, 4-, or 5-phenyl-substituted 2-(1-bromo-1-methylethyl)tetrahydrofurans 4a,c (75,90%, 36,96% de), which were not attainable as major products from polar, for example NBS-mediated, bromocyclizations. Aryl-substituted 2-iodomethyl tetrahydrofurans 5 (46,80%) were prepared in a similar way starting from N -alkenoxypyridine-2(1H)-thiones 7 and a suitable iodine atom donor. Diastereomerically pure iodides cis - 5 and trans - 5 served as starting materials for a stereochemical analysis of disubstituted tetrahydrofurans by NMR spectroscopy and X-ray diffraction analysis. The results of this investigation clarified that all new alkoxyl radical cyclizations followed in terms of regio- and diastereoselectivity the general guidelines which had been established for this type of ring-closure reaction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Kinetic analysis of a reactive model enediyne

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 9 2004
M. F. Semmelhack
Abstract A model framework related to the calcheamicin family of enediyne toxins was evaluated in its reactivity toward cycloaromatization through the arene 1,4-diyl intermediates and hydrogen atom abstractions. The keto version 9 is relatively unreactive, with t1/2,=,1.5,h at 60°C. The product from hydride reduction of the ketone, alcohol 13b, is much more reactive, with t1/2=50,min at 0°C. In both cases, the rate of rearrangement is independent of the hydrogen atom donor, consistent with a rate-determining first step (cyclization). Copyright © 2004 John Wiley & Sons, Ltd. [source]