Tungstophosphoric acid (H3PW12O40) as a heterogeneous inorganic catalyst. Activation of hexamethyldisilazane (HMDS) by tungstophosphoric acid for efficient and selective solvent-free O-silylation reactions

Electron‐deficient vanadium(IV) tetraphenylporphyrin: A new, highly efficient and reusable catalyst for chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane

“…One disadvantage of HMDS is its poor silylating power in the absence of a suitable catalyst, needing forceful conditions and long reaction times in many cases. [10] To solve this problem, a variety of catalysts, including (CH 3 ) 3 SiCl, [11] ZrCl 4 , [12] ZnCl 2 , [13] K-10 montmorillonite, [14] LiClO 4 , [15] H 3 PW 12 O 40 , [16] iodine, [17] InBr 3 , [18] zirconium sulfophenyl phosphonate, [19] CuSO 4 .5H 2 O, [20] sulfonic acid-functionalized nanoporous silica, [21] MgBr 2 ·OEt 2 , [22] LaCl 3 , [23] poly(N-bromobenzene-1,3-disulfonamide) and N,N,N ,Ntetrabromobenzene-1,3-disulfonamide, [24] Fe(TFA) 3 , [25] Fe 3 O 4 , [26] (n-Bu 4 N)Br, [27] trichloroisocyanuric acid (TCCA), [28] HClO 4 -SiO 2 , [29] Pd [30] and ZrO(OTf) 2 , [31] have been reported for trimethylsilylation of alcohols and phenols. Although these procedures provide an improvement, many of the catalysts or activators need long reaction times, drastic reaction conditions or tedious workups, or are moisture-sensitive or expensive.…”

Rapid, highly efficient and chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) catalyzed by reusable electron‐deficient tin(IV)porphyrin

“…In order to show the effectiveness of [Sn IV (TPP)(OTf) 2 ], different catalysts such as (CH 3 ) 3 SiCl, [9] ZnCl 2 , [11] K-10 montmorilonite, [12] H 3 PW 12 O 40 , [14] iodine, [15] InBr 3 , [16] CuSO 4 ž 5H 2 O [18] and (nBu 4 N)Br [25] were also used for trimethylsilylation of benzyl alcohol using the same amounts of catalyst, solvent and HMDS which was used with [Sn IV (TPP)(OTf) 2 ]. The results, which are summarized in Table 4, showed that [Sn IV (TPP)(OTf) 2 ] is more efficient than the others.…”

“…However, the main disadvantage of HMDS is its poor silylating power in the absence of a suitable catalyst which needs forceful conditions and long reaction times in many cases. [8] To solve this problem, a variety of catalysts including (CH 3 ) 3 SiCl, [9] sulfonic acids, [10] ZnCl 2 , [11] K-10 montmorilonite, [12] LiClO 4 , [13] H 3 PW 12 O 40 , [14] iodine, [15] InBr 3 , [16] zirconium sulfophenyl phosphonate, [17] CuSO 4 .5H 2 O, [18] sulfonic acid-functionalized nanoporous silica, [19] MgBr 2 ÐOEt 2 , [20] LaCl 3 , [21] poly(N-bromobenzene-1,3-disulfonamide) and N,N,N 0 ,N 0 -tetrabromobenzene-1,3-disulfonamide, [22] Fe(TFA) 3 , [23] Fe 3 O 4 , [24] (n-Bu 4 N)Br [25] and ZrO(OTf) 2 [26] have been reported. Although these procedures provide an improvement, many of these catalysts or activators need long reaction times, drastic reaction conditions or tedious workups, are moisture sensitive or have an expensive catalyst.…”

Rapid and efficient protection of alcohols and phenols, and deprotection of trimethylsilyl ethers catalyzed by a cerium‐containing polyoxometalate

“…The main drawback of HMDS is its poor silylating power which needs forceful conditions and long reaction times. Over the years, a variety of catalysts such as (CH 3 ) 3 SiCl, [6] silica chloride, [7] ZnCl 2 , [8] nitrogen ligand complexes of metal chlorides, [9] zirconium sulfophenyl phosphonate, [10] I 2 , [11] LiClO 4 , [12] K-10 montmorilonite, [13] tungstophosphoric acid, [14] poly(N-bromobenzene-1,3-disulfonamide), [15] CuSO 4 ·5H 2 O, [16] MgBr 2 ·OEt 2 , [17] LaCl 3 , [18] Fe(TFA) 3 , [19] Fe 3 O 4 , [20] (n-Bu 4 N)Br [21] and ZrO(OTf) 2 [22] have been reported for the silylation of hydroxyl groups using HMDS. However, in most of those reactions, long reaction times, drastic reaction conditions and the use of hazardous solvents or tedious work-up are needed.…”