C-H···Anion Interactions Assisted Addition of Water to Glycals by Sterically Hindered 2,4,6-Tri-tert-butylpyridinium Hydrochloride.

The conjugate acid of the bulky base 2,4,6-tri-tert-butylpyridine, under mild conditions, catalyzes the synthesis of silyl-protected 2-deoxy-hemiacetals and their dimerized products from glycals at varying concentrations of water. The criticality of the concentration of water in the reaction outcome is indicative of a unique mechanistic pathway for the bulky pyridine salt and not via the general Brønsted acid mechanism. The various silyl-protected hemiacetals thus synthesized were successfully utilized in the stereoselective synthesis of both α and β glycosides.