109669-64-9Relevant academic research and scientific papers
Cobalt-Catalyzed Epoxidation of Olefins. Dual Pathways for Oxygen Atom Transfer
Koola, J. D.,Kochi, J. K.
, p. 4545 - 4553 (2007/10/02)
Cobalt catalysis of olefin oxidation with tert-butyl hydroperoxide and iodosylbenzene as terminal oxidants is examined with CoII(Ia), where the ligand Ia is the bis-salicylamide dianion 2,3-bis(3,5-dichloro-2-oxybenzamido)-2,3-dimethylbutane.The catalytic epoxidation of norbornene with tert-butyl hydroperoxide and with iodosulbenzene proceeds via different pathways, since the former is effectively inhibited by ionol (2,6-di-tert-butyl-p-cresol) whereas the latter is not.A radical chain mechanism is proposed for tert-butyl hydroperoxide in which the homolytic addition of tert-butylperoxy radicals to the double bond leads to epoxidation.Cobalt catalysis is associated with the CoII/CoIII interconversion in the one-electron redox processes mediating the formation of the critical tert-butylperoxy radical.By contrast, there is no evidence for radical intermediates in the cobalt catalysis with iodosylbenzene which occurs readily with various types of olefins including 2-hexene, cyclooctene, β-methylstyrene, and even cyclohexene.A two-electron mechanism is proposed to account for the high reactivity, selectivity, and stereochemical retention in the catalytic epoxidation, despite the low solubility of CoII(Ia) in the reaction aspects of the cobalt-catalyzed epoxidations with iodosylbenzene.
