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Substituent Effects in the Vinylcyclopropane Radical Cation Rearrangement: A Computational Road to a New Synthetic Tool
Author(s) -
Oxgaard Jonas,
Wiest Olaf
Publication year - 2003
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200390204
Subject(s) - chemistry , substituent , cyclopropane , cyclopentene , steric effects , cope rearrangement , computational chemistry , radical ion , radical , stepwise reaction , concerted reaction , ring (chemistry) , medicinal chemistry , stereochemistry , organic chemistry , catalysis , reaction rate constant , kinetics , physics , quantum mechanics , order of reaction , ion
Abstract The effect of substituents on the rearrangement of vinylcyclopropane radical cation to cyclopentene was explored by density functional theory. Correlations have been established between the activation energy of the system and the nature, as well as the position, of the substituents. It was found that radical‐ or cation‐stabilizing substituents in select positions reduce the activation energy for the rearrangement substantially, while activation energies for competing hydrogen shifts were largely left unchanged. We have identified positions in the vinylcyclopropane where substitution is necessary, and others that can be substituted less discriminately. The mechanism of the rearrangement changes from stepwise to concerted when a strongly cation‐stabilizing substituent is used, because the first step in the stepwise reaction becomes a barrierless ring opening of a strained cyclopropane. Steric effects were also explored and have been found to be of crucial importance for the success of a rearrangement. Finally, a simple set of rules has been devised to predict the outcome of oxidation of a vinylcyclopropane without requiring detailed mechanistic investigations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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