Silicon amides

This synthetic method is of great importance in the synthesis of silicon amides. Halides of the type R SiCL,. (x = 0, 1, 2, 3) react with ammonia or primary and secondary amines to give the corresponding amides.17"24 Again, with sterically demanding amines only partial halide displacement is possible (equations 6 and 7).22,23... 

Nitramide. Sulphimide Carbamide. Silicon amide Silicon nitride... 

Compounds where fluorine is bound directly to silicon may be prepared duectly from sihcon tetrafluonde, obtamed by treatment of sihcon tetrachlonde with antimony tnfluonde and an alkyUithium or hthium amide base [99, 100] (equauon 80)... 

An alternative method for preparing phosphinous amides makes a profit on the high affinity between silicon and halogen atoms. This is the driving force of the reactions between halophosphanes and Ar-(trimethylsilyl)anilines, AT-(tri-methylsilyl)amides or AT-(trimethylsilyl)ureas and thioureas, as represented in the Scheme 6. In these processes the desired P-N bond and an halosilane are simultaneously formed [53,58-60]. 

Figure 1. Comparison between silicon and carbon substituted amides...

All studied model compounds can distinctly be divided into three groups (Table VII). The first group is composed of substances in which the sulfur, selenium or cyclopentadienyl anion acts as an anionic center. They exist only in open betaine forms, and their PES do not contain local minima corresponding to cyclic isomers. The second group contains compounds with arsonium cationic and oxide anionic centers and silicon and germanium betaines with arsonium and amide centers. They exist as cyclic isomers and their PES have no local minima corresponding to the open forms. Finally, the third group consists of six studied compounds with phosphonium cationic and oxide or amide anionic centers and arsonium-imide betaine. Their PES have minima for both cyclic and open forms separated by low barriers. 

The reaction described is of considerable general utility for the preparation of benzoyloxy derivatives of unsaturated hydrocarbons.2"8 Reactions of 2-butyl perbenzoate with various other classes of compounds in the presence of catalytic amounts of copper ions produce benzoyloxy derivatives. Thus this reaction can also be used to effect one-step oxidation of saturated hydrocarbons,9, 10 esters,6,11 dialkyl and aryl alkyl ethers,12 14 benzylic ethers,11,15 cyclic ethers,13,16 straight-chain and benzylic sulfides,12, 17-19 cyclic sulfides,11,19 amides,11 and certain organo-silicon compounds.20... 

The final step in this sequence is the coupling of a suitable chiral group to the silicone. In reaction scheme 3 the attachment of an amino acid amide residue is given as an example. The carboxy functional copolymer is dissolved in dichlormethane/dimethylformamide and an amino aid -amide is coupled with dicyclohexyl... 

In addition to silicon, sulfur groups have been used as auxiliaries for amide oxidation reactions (Scheme 31) [63], However, in these cases the mechanism of the reaction is different. The sulfur is oxidized to form a sulfur radical cation that is then eliminated from the molecule in order to... 

Si H M agostic interactions in silylamido complexes have been extensively studied to date. The earlier examples were prepared by halide displacement in the coordination sphere of a metal by a silylated amide, which puts severe limitations on the nature of the substituents at silicon (usually, robust methyl groups are used). More recently, a new route to p-agostic silylamides based on the direct coupling of silanes with imido ligands was discovered that allows one to trace the effect of substitution at silicon on the extent of the Si-H bond complexation (vide infra). 

Group-transfer polymerizations make use of a silicon-mediated Michael addition reaction. They allow the synthesis of isolatable, well-characterized living polymers whose reactive end groups can be converted into other functional groups. It allows the polymerization of alpha, beta-unsaturated esters, ketones, amides, or nitriles through the use of silyl ketenes in the presence of suitable nucleophilic catalysts such as soluble Lewis acids, fluorides, cyanides, azides, and bifluorides, HF. ... 

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