Silicon-containing nucleophiles

Compounds 561/562 were transformed into substituted tetrahydrofurans 563 in 23-51% yield by reaction with silicon-containing nucleophiles in the presence of On the... 

A remarkable regioselective and stereoselective double nucleophilic substitution of the acetal group of tefraacetal tefraoxa-cages (24a) with silicon-containing nucleophiles... 

Another class of silicon-containing polymers that have great potential to be extremely useful precursor materials are poly(chlorocarbosilanes).14f 46 Poly (chlorocarbosilanes) are not useful without modification because of the rapid hydrolysis of Si—Cl bonds, forming HC1 and an insoluble crosslinked polymer network. However, nucleophilic substitution of these Si—Cl bonds with various reagents produces materials widi a broad range of properties that are determined by the nature of the nucleophile used.47 Poly(chlorocarbosilanes) can be easily synthesized by ADMET (Fig. 8.18) without any detrimental side reactions, since the Si—Cl bond is inert to both catalysts 12 and 14. Early studies produced a polymer with Mn = 3000.14f... 

There arc many reactions in organic chemistry in which an Me3Si group acts like a proton—Chapter 47 will detail some more reactions of silicon-containing compounds. Just as acidic protons are removed by bases, silicon is readily removed by hard nucleophiles, particularly F" or RO-, and this can promote an elimination. An example is shown here. 

Sheehan and another Nobel laureate Khorana showed independently that the mild carbodiimide mediated synthesis is very useful in the condensation reaction of N-blocked amino acids with a different amino acid to form a peptide bond. The O-blocking of carboxylic acid groups in peptide synthesis with amino nucleophiles, such as glycine esters or amides, " or novel silicon containing protective groups is also mediated by carbodiimides. Likewise, alcohols are protected with 4-benzyloxybutyric acid, using EDC/DMPA. ... 

Compared to their carbon bioisosteres, silicon-containing molecules are more sensitive to hydrolysis and to nucleophilic attack in general, even when located in the center of a quaternary structure, the risk exists that the silicon atom will be attacked. Thus, l-chloro-l-sila-bicyclo-(2,2,l)-heptane can still be hydrolyzed by an attack on the vacant d orbital this attack is lateral and therefore possible even in the cases where the corresponding carbon derivative would have been inert toward a Sn2 reaction (Figure 15.69). 

The greater nucleophilic reactivity of silyl phosphites towards organohalogen compounds results in a greater complexity in product composition thus, dialkyl trimethylsilyl phosphites and CCI4 afford the dialkyl (trichloromethyl)phosphonates in yields of 50-60%, together with various halogenated silicon-containing products and a dialkyl phosphorochloridate (in up to 30% yield)". ... 

The silicon-containing Grignard reagents (27) and (28) are alkylated in high yield in the presence of Cu salts. The conversion of vinyl silanes via the epoxide into silyl enol ethers prompts the recognition of these reagents as examples of the two nucleophilic synthons for acetaldehyde (Scheme 23). 

Ruppert reagent (CFsSiMes) Carbonyl compounds (nucleophilic) Aromatics Safe and easy to handle Silicon-containing waste generated Expensive... 

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