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| - Thiyl Radical-Mediated Cleavage of Allylic C−N Bonds:Scope, Limitations, and Theoretical Support to theMechanism
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| - Thiols mediate the radical isomerization of allylic amines into enamines. The reaction results inthe cleavage of the allylic C−N bond, after treatment with aqueous HCl. The mechanism involves theabstraction of an allylic hydrogen α to nitrogen by thiyl radical, followed by a return hydrogen transfer fromthe thiol to the carbon γ to nitrogen in the intermediate allylic radical. The scope and limitations of thereaction with respect to the nature of the thiol, to the structure of the allylic chain, and to the nature of thesubstituents at nitrogen were investigated. The experimental results were interpreted on the ground ofDFT calculations of the C−Hα BDE in the starting allylic amines, and of the C−Hγ BDE in the resultingenamines. The efficiency of the initial hydrogen transfer is the first requirement for the reaction to proceed.A balance must be found between the S−H BDE and the two above-mentioned C−H BDEs. The incidenceof stereoelectronic factors was analyzed through NBO calculations performed on the optimized geometriesof the starting allylic amines. Additional calculations of the transition structures and subsequent tracing ofthe reaction profiles were performed for the abstraction of Hα from both the allyl and the prenyl derivativesby p-TolS•. The latter allowed us to estimate the rate constant for the abstraction of hydrogen by thiylradical from an N-prenylamine and an N-allylamine.
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