Catalytic Trimethylsilylation of alcohols and phenols by tribromoisocyanuric acid (TBCA) under mild and solvent free conditions

Protection step of active protic functional groups are frequently required in the synthesis of multifunctional compounds. The replacement of polar O–H bonds in alcohols and phenols with the O–Si linkage is of great importance across the chemical sciences. The silylation of hydroxyl groups to their corresponding trimethylsilyl ethers is a useful methodology in organic synthesis and materials science [1]. Among the various protecting groups used for hydroxyl function, the trimethylsilyl group is one of the popular methods. Several methods have become available for trimethylsilylation of the hydroxy functional group using a variety of silylating agents.1,1,1,3,3,3-Hexamethyldisilazane (HMDS) as a cheap, stable and commercially available material is one of the reagents that is used for the silylation of alcohols [2,3]. In continuation of our studies on catalytic application of N-halo compounds as organocatalyst in organic chemistry, we decided to report the catalytic application of tribromoisocyanuric acid (TBCA) as a new source of Br+ for the efficient silylation of a wide range of hydroxyl compounds under mild and solvent-free conditions (Figure 1).In order to show selectivity of this catalytic system, we tried several competitive reactions under similar conditions. The result shows that, the primary alcohol was completely converted to the corresponding trimethylsilyl ether, while 0% conversion was observed for the tertiary alcohol. Excellent selectivity was also observed for secondary alcohols in the presence of a tertiary alcohol. Similarly, this method showed excellent selectivity for the trimethylsilylation of phenol in the presence of aniline or thiophenol.