Substituent and solvent influence on the nature of the oxyallyl intermediate in the rearrangement of bicyclo[3.1.0]hex-3-en-2-ones

• Published in: Molecular physics Vol. 104; no. 5-7; pp. 889 - 901
• Main Authors: Gomez, I., Reguero, M.
• Format: Journal Article
• Language: English
• Published: Taylor & Francis Group 10.03.2006
• ISSN: 0026-8976; 1362-3028
• DOI: 10.1080/00268970500418026

The aim of this work is to elucidate the electronic nature of the oxyallyl intermediate in the rearrangement of bicyclo[3.1.0]hex-3-en-2-ones to cyclohexa-2,4-dienones. A number of derivatives of the parent cyclohexenone in gas phase and in a polar solvent have been studied using CASSCF/6-31G(d) calculations and the PCM model to take into account the solvent environment. The zwitterionic intermediate proposed by experimentalists has been theoretically localized for the first time. Results show that for all the derivatives, this intermediate is accessible only in polar solvents. On the other hand, only in the compound with a phenyl substituent in C 5 is the zwitterionic intermediate thermodynamically favoured over the diradical proposed by previous theoretical works on the subject.