Key Role of Ti(IV) in the Selective Radical−Radical Cross-Coupling Mediated by the Ingold-Fischer Effect

Autor:	Angelo Clerici, Ombretta Porta, Raffaele Spaccini, Nadia Pastori, Carlo Punta
Rok vydání:	2008
Předmět:	Reaction mechanism Chemistry Stereochemistry Radical General Chemistry Biochemistry Captodative effect Medicinal chemistry Catalysis Homolysis Coupling (electronics) Colloid and Surface Chemistry Chelation Stoichiometry Bond cleavage
Zdroj:	Journal of the American Chemical Society. 130:18018-18024
ISSN:	1520-5126 0002-7863
DOI:	10.1021/ja807613q
Popis:	We report an innovative approach for the selective synthesis of polyfunctional derivatives by cross-combination of different radicals generated under mild conditions. The coordinating effect of Ti(IV) plays a key role in the reaction mechanism: due to its chelating action on the hydroxyl groups, it promotes the homolytic C-C bond cleavage of alpha,beta-dihydroxy ketones by enhancing the captodative effect and the consequent stabilization of the corresponding alpha-hydroxy-alpha-carbonyl radicals. When these radicals are generated in the presence of stoichiometric amounts of TiCl(4) and 2,2'-azo-bis-isobutyronitrile (AIBN) is employed as a source of alpha-cyanoisopropyl radicals, the selective radical-radical cross-coupling is observed, affording the corresponding beta-hydroxynitriles in high yields. This innovative methodology allows application of the well-known Ingold-Fischer effect to a wider range of stabilized carbon-centered radicals, whose formation derives from the chelating action of Ti(IV).
Databáze:	OpenAIRE
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