NDLI: Copper -catalyzed atom transfer radical addition (ATRA) and cyclization (ATRC) reactions in the presence of environmentally benign ascorbic acid as a reducing agent

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Taylor, Matthew J. W. Eckenhoff, William T. Pintauer, Tomislav
Description	Author Affiliation: Taylor MJ ( Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Avenue, 308 Mellon Hall, Pittsburgh, PA 16282, USA.)
Abstract	In recent years, copper -catalyzed atom transfer radical addition (ATRA) has emerged as a viable organic procedure for the formation of carbon – carbon bonds starting from alkyl halides and alkenes. Studies have primarily focused on the use of free-radical initiators to regenerate the copper( I) complex or activator in situ. Although these initiators led to a significant decrease in the amount of metal catalyst , they were much less effective for highly active alkenes that readily undergo free- radical polymerization . In this study, the non-radical reducing agent ascorbic acid (commonly known as Vitamin C ) was effectively employed resulting in TONs as high as 15200 in the homogenous ATRA of polyhalogenated compounds to α-olefins, and enabling selective monoadduct formation for highly active alkenes such as acrylonitrile (TONs as high as 11800). As low as 7–20 mol% of ascorbic acid relative to substrate was sufficient for all ATRA and ATRC reactions examined. Further, product isolations for all selected syntheses were quite facile and nearly quantitative, requiring only simple liquid–liquid extraction techniques. Reactions in the presence of ascorbic acid were also examined kinetically $via^{1}H$ NMR and UV/Vis spectroscopy . A half order rate dependence on reducing agent concentration was observed, but the first order kinetic plots became nonlinear as the concentration of ascorbic acid was increased. Finally, the use of ascorbic acid circumvented otherwise necessary purging techniques, successfully furthering the utility of these reactions in organic synthesis.
ISSN	14779226
Issue Number	47
Journal	Dalton Trans.
Volume Number	39
e-ISSN	13645447
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2010-12-21
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Chemistry
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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