Selectivity study from the density functional local reactivity indices

Orbital and atomic chemical reactivity descriptors defined within density functional theory were applied to describe the selectivity of compounds used as reagents in two reactions of interest in organic synthesis. Mainly the values of orbital and atomic fukui indices for concurrent centers assumed to be involved in these reactions were rationalized and discussed. On the basis of their matching and mismatching the possibilities and limits to apply Pearson's hard-soft-acid-base principle are examined. It is shown that the methods employed for local (atomic and orbital) reactivity index computations can be applied very efficiently to predict the regioselectivity of carbon nucleophil addition reaction to enons. Unlikely, analysis of the atomic fukui indices of the concurrent centers in the nucleophil reaction of 3-(omega-bromoacetyl)coumarin with trisubstituted phosphites revealed that Pearson's principle is not applicable to understand the observed unusual regioselectivity of the 3-(omega-bromoacetyl)coumarin. Orbital hardnesses were also rationalized in terms of electron localization to describe in more details the reactivity of Rh atom in various nucleation positions on alpha-(0001) Al2O3 surface using a simple cluster model. (c) 2005 Published by Elsevier B.V.