Sterically Hindered and Electron-Deficient 2,4,6-Tri-tert-butylpyrimidinium as a π-Lewis Acid Toward Organocatalytic Silyl Protection of Carbohydrates Using Trialkyl/aryl Silanes.

We introduce the sterically hindered, strained/frustrated 2,4,6-tri-tert-butylpyrimidinium BArF as a mild and efficient organocatalyst for the silylation of alcohols. Silyl protection of carbohydrate alcohols utilizing trialkyl/aryl silanes for the first time has been achieved by employing an organocatalytic reagent, avoiding the usual basic and harsh conditions that involve silyl halides and triflates. The method also allows the organocatalytic reduction of aryl ketones. The unique π-acidic behavior of the highly electron-deficient 2,4,6-tri-tert-butylpyrimidinium salt in the protection of alcohols has been investigated via various control experiments.