Theoretical Studies on the Gas-Phase Wittig-Oxy-Cope Rearrangement of Deprotonated Diallyl Ether

摘要

The Wittig-oxy-Cope rearrangements of deprotonated diallyl ether, グ, CH2=CH-CH-O-CH2-CH=CH2, have been investigated theoretically by the AM1 method. A two step mechanism forming a Wittig product ion, ケ, (CH2=CH) (CH2=CH-CH2) CHO-, through a radical-pair intermediate was found to provide the most favored reaction pathway in the Wittig rearrangement. The subsequent oxy-Cope rearrangement from species ケ also involves a two step mechanism through a biradicaloid intermediate. The intramolecular proton transfer in グ (to form CH2=CH-CH2-O-CH-CH=CH2) is a higher activation energy barrier process compared to the Wittig and oxy-Cope rearrangements and is considered to be insignificant. These results are in good agreement with the condensed-phase as well as gas-phase experimental results.