Cross‐linked poly(4‐vinylpyridine/styrene) copolymer‐supported bismuth(III) triflate: an efficient heterogeneous catalyst for silylation of alcohols and phenols with HMDS

Abstract

Cross-linked poly(4-vinylpyridine/styrene) copolymer-supported bismuth(III) triflate ( 30 P/S-Bi) effectively activates hexamethyldisilazane (HMDS) for the silylation of alcohols and phenols. By the use of this heterogeneous catalytic system, a wide range of alcohols as well as phenols are converted into their corresponding trimethylsilyl ethers in high yield under mild reaction conditions. The catalyst was reused more than 10 times without significant loss of its catalytic activity.

A Highly Effective Route to Si−O−Si Moieties through O‐Silylation of Silanols and Polyhedral Oligomeric Silsesquioxane Silanols with Disilazanes

“…[73][74][75][76][77] Much of this effort has been focusedo nt he preparation and functionalization of SQs, [78][79][80][81][82][83][84] with ap articulare mphasis on applications in materialc hemistry. [26,27] According to the principles of green and sustainable chemistry,c atalysts should fulfil all following conditions:stability,reusability,availability,i nexpensiveness, and low toxicity.B i(OTf) 3 is more than capable of meeting these requirements. This slight differencei nr eactivity resulted because POSS silanols are bulkierr eagents.…”

“…The reaction might be more ef- ficient at an elevated temperature, but we decidedt op erform all reactions at RT.B i(OTf) 3 is well-known as an efficient and reusable catalyst, also for the O-silylation reaction. [26,27] According to the principles of green and sustainable chemistry,c atalysts should fulfil all following conditions:stability,reusability,availability,i nexpensiveness, and low toxicity.B i(OTf) 3 is more than capable of meeting these requirements.…”

“…Amongt his group, disilazanes, especially hexamethyldisilazane (HMDS), seem to be very effective for the silylationo fÀOH groups and have several advantages over other silylating agents, including mild reaction conditions as well as the formation of ammonia as sole byproduct. Although inorganic materials, [19][20][21][22] alcohols, [23][24][25][26][27][28][29][30] phenols, [26][27][28][29] carbohydrates, [29] carboxylic acids, [31] oximes, [32] ande ven thiols [33] have been successfully silylated by various disilazanes, the use of these silylatinga gents in O-metalation of simple silanols and polyhedralo ligomeric silsesquioxane (POSS) silanols has never been comprehensivelys tudied.T herea re only few examples: Lebedeve tal. synthesized two unsymmetricald isiloxanes by utilizingd isilazanes in ar eactionw ith two compounds such as triphenylsilanol and diphenylsilanediol.…”

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

“…The silylation of alcohols and phenols catalyzed by Cross-linked poly (4-vinylpyridine/styrene) copolymer-supported bismuth (III) triflate ( 30 P/S-Bi) under mild reaction conditions was reported by Lee and Kadam. [121] In this method, 1 mol% of 30 P/S-Bi as an efficient and recyclable heterogeneous catalyst and HMDS were used for the silylation of a wide range of alcohols, phenols, and benzyl alcohols and, finally, produced the excellent yields of corresponding TMS ethers products in dichloromethane in under mild conditions. (Scheme 23).…”

Separation of ursodeoxycholic acid by silylation crystallization

“…Silylation is a powerful tool to improve the production process and the quality of the product in modern pharmaceutical and organic synthesis, and has been applied in increasing the volatility [13], changing the solubility in organic solvents [14], and the protection of sensitive functional groups such as hydroxyl and carboxyl moieties [15]. Silylation of alcohols and phenols with hexamethyldisilazane (HMDS) has been achieved using various types of catalysts [16][17][18][19][20][21]. The reaction conditions were nearly neutral, and the corresponding silyl ethers yields were high.…”