Trityl silanes

A diaryldihydrosilane with a hexacoordinated silicon center, produced through intramolecular coordination, is reported not to react with benzaldehyde, although the silane is capable of reducing silver ion to silver metal.113 There is also a report of a heptacoordinate silicon hydride species with the ability to transfer hydride to trityl cation while remaining inactive toward methanol.108114... 

ALKENES Alkyl diphenyl phosphonates. o-Chloroallyllithium. Chlorotrynethyl-silane-Sodium iodide. Grignard reagents. Otganocuprates. Triphenylphosphine-lodoform-Imidazole. Trityl tetrafluoro-borate. 

X = TPFPB) in benzene solution fail because the bulky mesityl groups prevent a trityl cation to come close enough to abstract a hydride ion from the silane Mes3SiH. 

The hydride in silanes ArSiR2H can be abstracted by the trityl cation, leaving principally a silicenium ion. This highly electrophilic species interacts with the anion associated with the trityl cation either by coordination (e.g., CIO4 ) or by halide abstraction (e.g., BF4 ) [3]. 

During cleavage of A -trityl derivatives protonation of the annino group is sufficient to prevent its realkylation by the trityl cations alternatively, addition of reducing silanes as... 

The O-trityl protection can be removed under the same conditions as used for cleavage of peptides from 2-chlorotrityl resin, i.e. with ACOH/TFE/CH2Q2 (2 2 6, rt, 1 h) as the cleavage nnixture or with 1% TFA without affecting tert-butyl side-chain protection. Silanes are added as hydride donors to scavenge the trityl cations and to avoid retritylation. Most commonly, the trityl derivatives of tyrosine, serine, and threonine are used for the synthesis of phosphopeptides by postsynthetic methods on a solid support. In contrast to the use of protected phosphoamino acid derivatives, such as Fmoc-Tyr(POOBzl)-OH,f l both the phosphorylated and nonphosphorylated peptides can be prepared from one syn-... 

The synthesis of these materials starts with the reaction of chlorodimethyl-(2,3,4,5-tetramethyl-2,4-cyclopentadien-l-yl)silane (Cp -silane) with the snrface amine groups. It was shown that the percentage of amine sites reactive toward the Cp -silane was significantly better for the trityl-spaced material than traditionally prepared aminosilica (77% reacted amines vs. 29% reacted amines) [19]. Also, once the Cp -silane moiety was reacted with the trityl-spaced amines, the percentage... 

The benzyl-spaced aminosilica was also used as a scaffold on which to anchor CGC-inspired catalysts [19]. As in the trityl-spaced study, the aminosilica was first reacted with Cp -silane. For the benzyl-spaced materials, complete conversion of the amine groups through reaction with the Cp -silane did not occur however, the amine conversion for this material was twice the amine conversion for the traditionally grafted material (63% reacted amines vs. 29% reacted amines) [19]. When the grafted, metallated catalyst was tested for polymerization of ethylene, the benzyl-spaced catalyst again outperformed the traditionally grafted material, although it was somewhat less active than the trityl-spaced immobilized catalyst. 

Cleavage of the MOM group with dilute acids or with PPTS in r-BuOH regenerates the alcohol. A mild and selective reagent for removing the MOM group in the presence of methyl or benzyl ethers, -SiPh2 -Bu ethers, or esters is bromotrimethyl-silane. However, TMSBr will also cleave acetals and trityl ethers. ... 

In the case of triphenylsilane and trityl chloride, this reaction is first order in both reactants in benzene (233). The reaction rate for modified substrates indicates that with respect to R3CX, rate is a function of proclivity to ionize, trityl halides being more rapid than benzhydryl or allyl or tcr/-butyl halides. Indeed the latter required the presence of BBr3 as a catalyst. Within a given series. Cl > Br > I, phenylsilanes react more rapidly than alkyl silanes. A mechanism involving simultaneous nucleophilic attack of halide on silicon, and electrophilic attack on hydrogen by the carbonium ion is reasonable,... 

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