Mild and efficient silylation of alcohols and phenols with HMDS using Bi(OTf)3 under solvent-free condition

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.…”

“…Based on the known literature, [26,36] mechanisms of all transformationsa re illustrated in Figures 5a nd 6. The silylation by HMDS proceeds through the formation of af our-centered transition state and is followed by an ucleophilic attack of oxygen toward the silicon atom in the HDMS molecule.…”

“…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.…”

Sulfonated Ordered Nanoporous Carbon (CMK-5-SO3H) as an Efficient and Highly Recyclable Catalyst for the Silylation of Alcohols and Phenols with Hexamethyldisilazane (HMDS)

“…Even though the handling of this reagent is easy, its main drawback is its poor silylating power which needs forceful conditions and long reaction times in many instances [12]. Therefore, a variety of catalysts have been developed for activation of this reagent, such as sulfuric acid [1,2], (CH 3 ) 3 SiCl [13], sulfonic acids [14], K-10 montmorilonite [15,16], iodine [17], tungstophosphoric acid (H 3 PW 12 O 40 ) [18], LiClO 4 [19], Mg(OTf) 2 [20], CuSO 4 Á5H 2 O [21], TBBDA, and PBBS [22], [PdCl(g 3 -C 3 H 5 )] 2 -PPh 3 [23], MgBr 2 ÁOEt 2 [24], InBr 3 [25], LaCl 3 [26], HReO 4 [27], silica supported perchloric acid [28], trichloroisocyanuric acid [29], Fe(F 3 CCO 2 ) 3 [30], Zr(OTf) 2 [31], Bi(OTf) 3 [32], and TiCl 2 (OTf)-SiO 2 [33]. Although several of these procedures are useful, some of them suffer from the use of homogenous and often corrosive catalyst, tedious workup and long reaction times.…”