ChemInform Abstract: Control of the Relative Electrophilicity of Alkylating Agents by Variation of the Lewis Acid Concentration.

ChemInform Abstract

From the relative rates of competing alkylations as given in the scheme two cases are derived. A) If the carbenium ion (II) is less stabilized than the cation of product (IV), at least equivalent amounts of a completely ionizing Lewis acid are required for selective formation of the 1:1 products (IV); B) if, however, the carbenium ion (II) is better stabilized than the cation of (IV) (i.e. ΔG°_ionization (I) < ΔG°_ionization (IV)) highest selectivity in the formation of 1:1 products (IV) is attained with catalytic amounts of the weakest possible Lewis acid.