Polystyrene‐Gallium Trichloride Complex: A Mild, Highly Efficient, and Recyclable Polymeric Lewis Acid Catalyst for Chemoselective Silylation of Alcohols and Phenols with Hexamethyldisilazane

Abstract

Polystyrene‐supported gallium trichloride (PS/GaCl3) as a highly active and reusable heterogeneous Lewis acid effectively activates hexamethyldisilazane (HMDS) for the efficient silylation of alcohols and phenols at room temperature. In this heterogeneous catalytic system, primary, secondary, and tertiary alcohols as well as phenols were converted to their corresponding trimethylsilyl ethers with short reaction times and high yields under mild reaction conditions. The heterogenized catalyst is of high reusability and stability in the silylation reactions and was recovered several times with negligible loss in its activity or a negligible catalyst leaching, and also there is no need for regeneration. It is noteworthy that this method can be used for chemoselective silylation of different alcohols and phenols with high yields.

A novel route for synthesis of cross-linked polystyrene copolymer beads with tunable porosity using guar and xanthan gums from bioresources as alternative synthetic suspension stabilizers

“…In continuation of recent works on the use of polymeric catalysts in organic transformations [43,54–57] and continued seeking for suitable polymer supports to immobilize catalysts on them, herein, this contribution describes in detail the use of eco-friendly suspending agents from bioresouces, guar and xanthan gums as stabilizing agents in suspension polymerization reactions, as well as their influence on the size and surface area of the synthesized polymer particles. For the purposes of this work, the synthesis of poly(St- co -DVB) cross-linked beads was chosen as the main suspension polymerization system to be studied.…”

Recent advances in catalytic silylation of hydroxyl‐bearing compounds: A green technique for protection of alcohols using Si–O bond formations

“…In this regard, Rahmatpour et al reported a catalytic and chemoselective silylation of hydroxyl group of alcohols and phenols using HMDS in the presence of polystyrenesupported gallium trichloride (PS/GaCl 3 ) as a highly active and reusable heterogeneous polymeric Lewis acid Catalyst for the activation of HMDS in dichloromethane. [125] In the mentioned research, over 29 examples of primary, secondary, and tertiary alcohols as well as phenols were studied, and their corresponding TMS ethers were obtained with short reaction times and good-to-excellent yields from 88% to 98% under mild reaction conditions, where only three substrate did not react (Scheme 32). Regarding the heterogenized catalyst, there was no need for regeneration.…”

“…Moreover, it was highly reusable and stable in the silylation reactions and was recovered several times with negligible loss in its activity or a negligible catalyst leaching. [125] It is worth mentioning that the method can be used for chemoselective silylation of different alcohols and phenols with high yields.…”