Synthesis of a Chiral Borate Counteranion, Its Trityl Salt, and Application Thereof in Lewis‐Acid Catalysis

Abstract

The preparation of a chiral derivative of [B(C6F5)4]– in which the fluorine atom in the para position of each of the C6F5 groups is replaced by a 1,1′‐binaphthalen‐2‐yl group is described. The new counteranion was isolated as its lithium, sodium, and trityl salts. The chiral trityl salt was then used as a catalyst in selected counteranion‐directed Diels–Alder reactions and a Mukaiyama aldol addition, but no asymmetric induction was achieved. Application of the chiral trityl salt to the generation of silicon cations by silicon‐to‐carbon hydride transfer from hydrosilanes failed, presumably as a result of the incompatibility of the relatively electron‐rich naphthyl groups in the borate and the cationic silicon electrophiles.