ELECTRONIC CONTROL OF STEREOSELECTIVITY .2. STEREOCHEMICAL METHOD FOR QUALITATIVELY ASSESSING THE RELATIVE ELECTROPHILICITY OF VARIOUS ELECTRON-DEFICIENT SPECIES

Those trends observed in nucleophilic reactivity appear to be predetermined in large part by the intrinsic basicity and polarizability of the reagent as attested to by the quantitative equations developed by Swain and Scott and by Edwards. Striking for its absence is any comparable relative ordering of electrophilicity. This is due principally to the fact that the fundamental nature of SN2 reactions permits the direct replacement of one nucleophile by another via transition states where both are intimately involved. No similar electrophilic process is available. Although a principal tenet of the selectivity relationship for electrophilic aromatic substitution relates a lessening of electrophile reactivity to an increase in positional selectivity, the procedures involved in this type of data acqui-sition are less than direct. As part of a systematic study of stereoelectronic control, we have uncovered a new, one-step technique capable of qualitatively ranking the electrophilicity of various electron-deficient species by means of a simple stereochemical citerion. © 1979, American Chemical Society. All rights reserved.