Zur elektrocyclischen Ringöffnung von Cyclopropylhalogeniden bei der Reaktion mit Natriumiodid in Aceton / Electrocyclic Ring Opening of Cyclopropyl Halides in the Course of their Reaction with Sodium Iodide in Acetone

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Abstract
Reaction of cyclopropyl halides with sodium iodide in acetone (i.e. under typical SN2-conditions), proceeds via ring opening to allylic systems finally yielding 1,5-hexadienes upon dimerisation; ring-retained products were not detected. Application of the Wood-ward-Hoffmann rules lends strong support to a cationic synchronous mechanism. This is also confirmed by kinetic measurements proving this reaction to be first order over all. The kinetic data are shown to fit the Hammett equation using σ-values for cyclopropyl bromides and σ+-values for geminal cyclopropyl dichlorides, respectively. The validity of the Woodward-Hoffmann-De Puyrule (according to which in synchronous reactions leaving groups situated endo are strongly favored over those situated exo) is tested in corresponding experiments involving condensed ring systems.

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