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oai:gredos.usal.es:10366/1541482025-04-30T19:51:19Zcom_10366_4155com_10366_4055com_10366_3946com_10366_3823col_10366_4156

Mateos Burón, Lydia Rabanedo Clemente, R. Fernández Mateos, Alfonso Herrero Teijón, Pablo Rubio González, María Rosa 2024-01-11T17:19:16Z 2024-01-11T17:19:16Z 2007 Fernández Mateos, A., Herrero Teijón, P., Mateos Burón, L., Rabanedo Clemente, R. & Rubio González, R. (2007). On the Mechanism and Kinetics of Radical Reactions of Epoxyketones and Epoxynitriles Induced by Titanocene Chloride. The Journal of Organic Chemistry, 72(26), 9973-9982. https://doi.org/10.1021/jo701497e 0022-3263 http://hdl.handle.net/10366/154148 10.1021/jo701497e 1520-6904 [EN]The reactions of a series of epoxynitriles and epoxyketones induced by titanocene chloride have been studied. The kinetics of the decyanogenation of β,γ-epoxynitriles with Ti(III) corresponds to a radical reaction (k25 ≈ 106 s-1), as demonstrated by competition experiments with H-transfer from 1,4- cyclohexadiene (1,4-CHD) or PhSH or conjugate addition to acrylonitrile. The 5-exo cyclization onto nitrile induced by Ti(III) is a radical reaction (k25 ≈ 107 s-1) as seen in competition experiments with H-transfer from PhSH or the titanocene-water complex. The iminyl or alkoxyl radicals generated by 5-exo cyclization onto nitriles or ketones only undergo a reduction with Ti(III). This reaction overwhelms any alternative process, such as tandem cyclization onto alkenes or β-scission. Iminyl radicals generated by 4-exo cyclizations onto nitriles undergo reduction with Ti(III) and β-scission reaction in a ratio of 96:4 when the R-substituent is CN. Alkoxyl radicals from 4-exo cyclizations onto ketone carbonyls undergo reduction with Ti(III) and β-scission in a ratio of 60:40 when the R-substituent is COOR. In nearly all the reactions studied, the role of Ti(III) is triple: a radical initiator (homolytic cleavage of oxirane), a Lewis acid (coordination to CN or CdO), and a terminator (reduction of iminyl or alkoxyl radicals). eng http://creativecommons.org/licenses/by-nc-nd/4.0/ info:eu-repo/semantics/openAccess Attribution-NonCommercial-NoDerivatives 4.0 Internacional Reacciones químicas Radicales (Química) Química orgánica On the Mechanism and Kinetics of Radical Reactions of Epoxyketones and Epoxynitriles Induced by Titanocene Chloride info:eu-repo/semantics/article