Quantitative characterization of the global electrophilicity power of common diene/dienophile pairs in Diels-Alder reactions

The global electrophilicity power, omega, of a series of dienes and dienophiles commonly used in Diels-Alder reactions may be conveniently classified within a unique relative scale. Useful information about the polarity of transition state structures expected for a given reaction may be obtained from the difference in the global electrophilicity power, Deltaomega. of the diene/dienophile interacting pair. Thus the polarity of the process can be related with non-polar (Deltaomega small, pericyclic processes) and polar (Deltaomega big, ionic processes) mechanisms. (C) 2002 Elsevier Science Ltd. All rights reserved.