Trimethylsilyl perchlorate

Kusumoto and coworkers have found that the treatment of hemiacetal 1 with trifluoro- or trichloroacetic anhydride 94 (1 equiv) and trimethylsilyl perchlorate (0.2 equiv) selectively provides the corresponding anomeric ester intermediate 91 [152], Hemiacetal acylation occurs even in the presence of the alcohol acceptor. With Lewis acid assistance, the glycosyl ester intermediate is displaced to provide disaccharide products in good yields. This transformation allowed the synthesis of disaccharides 98 (81%) and 99 (91%). In some cases, acetic anhydride has been used as the electrophilic activator of hemiacetal donors and the reaction with thiol acceptors yields S-linked glycosides [153,154],... 

Wannagat, U. et al., Z. Anorg. Chem., 1950, 302, 185-198 Several trialkyl- or triaryl-silyl perchlorates explode on heating, including Triethylsilyl perchlorate, 2562 Tri-4-methylphenylsilyl perchlorate, 3823 Trimethylsilyl perchlorate, 1302... 

Yamashiro et al. 1972), boron trifluoride etherate in acetic acid (Schnabel et al. 1971), trimethylsylil triflate (Schmidt et al. 1987), trimethylsilyl perchlorate (Vorbrueggen Krolikiewicz 1975), and, most frequently, trifluoroacetic acid (Farowicki Kocienski 1995 and references therein). Deprotection of the /-HOC group under neutral conditions was not described until recently, yet it is highly desirable. Now it has been found that the tert-butoxycarbonyl protecting group for amines, alcohols, or thiols is removed efficiently (90-99% yield) with use of 0.2 equivalent of cerium ammonium nitrate in acetonitrile at 80°C (Hwu et al. 1996) ... 

Trimethylpyrilium perchlorate, 2987 Trimethylsilylacetylene, see 1-Trimethylsilylethyne, 1976b Trimethylsilyl chlorochromate, 1297 Trimethylsilyl hydroperoxide, 1326 Trimethylsilylmethyllithium, 1716 Trimethylsilyl perchlorate, 1298... 

Protodesilylation of allyl- or aryl-substituted trialkylsilanes with an acid partner is a cleaner method, producing propene or an aromatic hydrocarbon as a volatile inert byproduct. Although some methods of isolation have been reported, they can usually be prepared in situ in aprotic media and employed without further purification. Methods of preparation of representative organosilicon Lewis acids, la, trimethylsilyl bis(trifluoro-methanesulfone)imide (7) [9], trimethylsilyl perchlorate (6a) [10], iodotrimethylsilane, and trimethylsilyl tetrakis(trifluoromethanesulfonyl)borate [11] are described below. In principle, these analogs are also accessible in a similar manner (Table 1) [2d]. 

Triethylsilyl perchlorate, 2562 Tri-4-methylphenylsilyl perchlorate, 3823 Trimethylsilyl perchlorate, 1302... 

Synthesis of nucleosides. Reaction of shylated heterocycles with a protected 1-0-acyl or 1-0-alkyl sugar in 1,2-dichloroethane with either trimethylsilyl perchlorate or trimethylsilyl trifluoromethanesulfonate, (013)3810802-CF3, as catalyst gives nucleosides in high yield. The reaction is formulated for the reaction of silylated uracil (1) with l-0-acetyl-2,3,5-tri-0-benzoyl- 3-D-ribofuranose (2) either at 22 for a prolonged period or for 4 hr. at reflux temperature. The function of the catalyst is to convert the sugar into the glycosyl... 

Mild Deprotection of Boc Protecting Group. The Boc protecting group is used throughout peptide chemistry. Common ways of removing it include the use of 50% Trifluoroacetic Acid in CH2CI2, Trimethylsilyl Perchlorate, or lodotrimethylsilane... 

One of the better processes for the conversion of adenine to adenosine involves the initial conversion of adenine to the corresponding N -benzoyl derivative with benzoyl chloride in pyridine. Then, as shown in Scheme 12.100, silylation with trimethylchlorosilane in hexamethyldisilazane [(CH3)3Si]2NH solvent at reflux yielded a silyl derivative that was heated in 1,2-dichloroethane (CICH2CH2CI) at reflux with trimethylsilyl perchlorate [(0113)3810104] and l-0-acetyl-23,5-tri-0-benzoyl-P-D-ribofuranose for 12 h. The resulting crude, protected adenosine was converted to unprotected material by standing at room temperature with methano-lic ammonia followed by recrystaflization from aqueous methanol. 

The activation of the anomeric acetoxy group affords the intermediate oxonium ion 105 stabilised by the perchlorate ion. This large counter anion blocks the P-face of the anomeric centre silyl alkoxide attack from the a-face predominantly produces the a-glucoside along with trimethylsilyl perchlorate and MCIn- OAc, from which the catalyst is regenerated. 

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