Association of Pyramidal Boron Lewis Superacids with Pyridines: Bending 2,4,6‐Collidine with the 10‐Sulfonium‐9‐boratriptycene

Abstract

Dedicated to Prof Doug Stephan on the occasion of his 70 th BirthdayThe association of pyridine and of 2,4,6-trimethylpyridine (collidine) with a pyramidal triarylborane belonging to the 9boratriptycene family is investigated by NMR spectroscopy and by X-ray diffraction analysis. Despite of the large size of the ortho-disubstituted collidine Lewis base and of the large steric hindrance of the boron Lewis superacid used (9-boratriptycene-10-sulfonium), the superacidity at its boron atom is enabling the formation of a B-N bond and is resulting in a very stabe Lewis adduct. Single-crystal X-ray diffraction analysis revealed [a] A.