Unravelling the Mechanism of Non-photoactivated 2+2 Cycloaddition Reactions: Relevance of Orbital Interactions and Zwitterionic Intermediates

摘要

abstract_textpIn this work, a thorough theoretical study of the 2+2 cycloaddition reaction between asymmetric substituted alkenes is presented. The simulations evidence a concerted asynchronous or stepwise mechanism, depending on the nature of the electron-deficient alkene. We have found a direct relation between the interaction of the frontier-orbitals (HOMO-LUMO) and the distortion energy with the activation energy (whose values oscillate between -4 and -35 kcal/mol in the studied cases). We thus conclude that the interaction between the frontier-orbitals govern the reaction, through changes in the distortion energy. We also show that the lifetime of the zwitterionic intermediate determine the relative stereochemistry of the products./p/abstract_text