92285-04-6Relevant articles and documents
The Use of 5-Halocyclooctenes as a Radical Probe. Reactions with Lithium Aluminum Hydride
Ashby, E.C.,Pham, Tung N.
, p. 3598 - 3602 (1986)
The 5-halocyclooctenes have been studied as a radical probe in their reactions with lithium aluminum hydride (LiAlH4) in order to detect the occurrence of radical intermediates and also to evaluate the effectiveness of these compounds as radical probes.Also the 4-cyclooctenyl radical was trapped by dicyclohexylphosphine (DCPH), dicyclohexylphosphine deuteride (DCPD), and cyclohexadiene.For the iodide, and to a lesser extent the bromide, radical intermediates were found to be a major component in the reaction since the bicyclo hydrocarbon was the major product.No evidence for radical intermediates was found for reactions of the correspon ding chloride or tosylate with LiAlH4.It is concluded that 5-iodocyclooctene is an effective radical probe for those reactions where radical intermediates are involved
Evidence for Single Electron Transfer in the Reactions of Lithium Dimethylcuprate with Alkyl Halides
Ashby, E. C.,Coleman, David
, p. 4554 - 4565 (2007/10/02)
A variety of methods have been utilized to explore the occurence of radical intermediates and free-radical chain processes initiated by electron transfer in the reactions of lithium dimethylcuprate with alkyl halides.The effect of leaving group, nature of the cuprate species, and ratio of cuprate to substrate, solvent, hydrogen atom donor, and other additives on the rate of and product distribution were investigated by using a cyclooctenyl radical probe.The presence of significant amounts of radicals strongly supports single electron transfer (SET) as a major pathway for the reaction of secondary iodides with LiCuMe2.There is some evidence of single electron transfer also accurring with secondary bromides, but tosylates appear to be reacting entirely by a SN2-like pathway.The role of dicyclohexylphosphine (DCPH) as an additive in the reaction was investigated with the result that it was shown to be capable of behaving in a unique manner depending on wheter the substrate is an alkyl iodide or bromide.The product distribution, rate, and effect of p-dinitrobenzene on the reaction of 5-iodo-1-cyclooctene were compared with three other probes and the results demonstrate that at least three reaction pathways are involved to varying degrees.These pathways could involve the initiation of free radicals or radical anion (SRN1) chain processes. these studies also demonstrate how changes in the substrate can alter the predominant reaction pathways that are followed.
Evidence for Single Electron Transfer in the Reduction of Organic Halides by Lithium Triethylborohydride
Ashby, E.C.,Wenderoth, Bernd,Pham, Tung N.,Park, Won-Suh
, p. 4505 - 4509 (2007/10/02)
Product studies involving the reduction of cyclizable alkyl iodides and bromides, trapping of intermediate radicals by dicyclohexylphosphine, and direct EPR observation of radicals have been used to detect the occurence of a single electron transfer pathway in the reduction of these halides by lithium triethylborohydride.
