MNDO (Modified Neglect of Differential Overlap) Study of the Claisen Rearrangement

摘要

MNDO (Modified Neglect of Differential Overlap) calculations are reported for the Claisen rearrangement of 3-oxa-1-hexene, for its various methoxy and cyano derivatives, and for the 2-methoxy-5-cyano derivative. The reactions are found to take place by a two-stage mechanism, analogous to that of the Cope rearrangement of 2,5-hexadiene but where the intermediate biradicaloid is not a stable species, undergoing conversion to the product without activation. The results agree with the available evidence concerning substituent effects and lead to verifiable predictions.