Tailoring of strong neutral organic superacids: DFT-B3LYP calculations on some fulvene derivatives

Abstract

The design of new powerful neutral superacids is of great importance in organic chemistry. It is shown by using a reliable theoretical model that cyano derivatives of fulvene provide very good candidates for potent organic superacids. The origin of the high acidity is identified as the aromatization of the five-membered ring upon deprotonation. Their acidity is enhanced by the Lewis acid-base interaction between a –CH₂–CH₂–CH₂–BX₂ chain and the anionic O⁻ center in the corresponding conjugate bases. X stands here for F, Cl and Br atoms. There are good reasons to believe that the proposed neutral organic superacids are amenable to laboratory preparation.