Solvent and Catalyst-Free Synthesis of Silicon-Protected Alcohols

The protection reactions of alcohols (primary and secondary) were efficiently performed applying silyl chlorides (Me3SiCl, Et3SiCl, t-BuMe2SiCl and t-BuPh2SiCl) as protecting source, on grinding, without the use of a catalyst. The reactions proceeded smoothly, either at room temperature or at 40 degrees C, depending on the protecting group applied, and under solvent-free conditions. In comparison with the classical reaction conditions, which employ, most of the times, solvent in anhydrous conditions (tetrahydrofuran or N,N-dimethylformamide), this synthetic protocol exhibits the advantages of shorter reaction times, milder reaction conditions, higher yields and simpler purification steps. Under this method 21 examples could be obtained at short reaction times (5 - 10min) and presenting up to 98% of yields. When the substrate was a diol bearing primary and phenolic hydroxyl moieties, the monoprotected or the diprotected product could be obtained as a sole product, in excellent yields.