Chiral Modification of the Tetrakis(pentafluorophenyl)borate Anion with Myrtanyl Groups

The synthesis and characterization of chiral [B(C6F5)4]– derivatives bearing a myrtanyl group instead of a fluoro substituent in the para position are described. These new chiral borates were isolated as their bench‐stable lithium, sodium, and cesium salts. The corresponding trityl salts were prepared and tested as catalysts in representative counteranion‐directed Diels–Alder reactions and Mukaiyama aldol additions but no enantioselectivity was obtained. Preformation of a chalcone‐derived silylcarboxonium ion with the chiral borate as counteranion did not lead to any asymmetric induction in a reaction with cyclohexa‐1,3‐diene. New chiral versions of the ubiquitous [B(C6F5)4]– anion decorated with myrtanyl backbones and paired with various countercations are presented (Tr = Ph3(4‐Tol)C). Their use as catalysts in Diels–Alder reactions and Mukaiyama aldol additions is demonstrated, and their stability against highly electrophilic silylium‐ion‐like species is investigated.