Silyl perchlorates, hydrolysis

Treatment of highly sterically hindered iodosilanes with a silver salt in a solvent containing water has also been used successfully to prepare bulky silanols (Scheme 6). The introduction of the OH group seems to occur not only by hydrolysis of the silyl perchlorates formed, but also by reaction of the bridged silicocationic species that are formed as intermediates in this type of reaction (62). The reaction... 

Scheme 11 summarizes the reactions of bis(diisopropylamino)lithiocyclopropenylium perchlorate with a variety of electrophiles. These include acid hydrolysis, silylation, oxidative coupling with iodine to the symmetrical tetraisopropylamino triafulvalene dica-tion, reaction leading to C—C bond formation, with electrophilic allenes to give a zwitterionic dihydrotriafulvenes, with disubstituted cyclopropenylium perchlorate, and... 

Reductive coupling of carbonyls to alkenes Titanium(IV) chloride-Zinc, 310 of carbonyls to pinacols Titanium(III) chloride, 302 Titanium(IV) chloride-Zinc, 310 of other substrates Samarium(II) iodide, 270 Reductive cyclization 2-(Phenylseleno)acrylonitrile, 244 Tributylgermane, 313 Tributyltin hydride, 316 Triphenyltin hydride, 335 Trityl perchlorate, 339 Reductive hydrolysis (see Hydrolysis) Reductive silylation Chlorotrimethylsilane-Zinc, 82... 

Mukaiyama aldol reactions using a catalytic amount of a Lewis acidic metal salt afford silylated aldols (silyl ethers) as major products, but not free aldols (alcohols). Three mechanistic pathways which account for the formation of the silylated aldols are illustrated in Scheme 10.14. In a metal-catalyzed process the Lewis acidic metal catalyst is regenerated on silylation of the metal aldolate by intramolecular or intermolecular silicon transfer (paths a and b, respectively). If aldolate silylation is slow, a silicon-catalyzed process (path c) might effectively compete with the metal-catalyzed process. Carreira and Bosnich have concluded that some metal triflates serve as precursors of silyl triflates, which promote the aldol reaction as the actual catalysts, as shown in path c [46, 47]. Three similar pathways are possible in the triarylcarbenium ion-catalyzed reaction. According to Denmark et al. triarylcarbenium ions are the actual catalysts (path b) [48], whereas Bosnich has insisted that hydrolysis of the salts by a trace amount of water generates the silicon-based Lewis acids working as the actual catalysts (path c) [47]. Otera et al. have reported that 10-methylacridinium perchlorate is an efficient catalyst of the aldol reaction of ketene triethylsilyl acetals [49]. In this reaction, the perchlorate reacts smoothly with the acetals to produce the actual catalyst, triethylsilyl perchlorate. 

---