Silylimidazole, trimethyl

A recent example of the use of silylating agents in the derivatization of polymer surfaces is given by Davies and Munro s application of trimethyl-silylimidazole (TMSI) to polyfacrylic acid) (PA A) surface analysis [35]. Figure 5 shows the changes in core level XPS spectra for PA A after reaction with TMSI. Williams first proposed the use of TFSA for this purpose in 1981 [36] but this application was not subsequently published so we take this opportunity to provide more detail. 

Among the more important trimethylsilylation reagents are trimethylchloro-silane (TMCS) hexamethyldisilazane [(Me3Si)2NH, (HMDS)] iV-trimethyl-silylimidazole (TMSI) (1) AT,0-bis(trimethylsilyl)acetamide (BSA) (2) AT,0-bis(trimethylsilyl)trifluoroacetamide (BSTFA) (3) and A-methyl-A-(t-butyldimethylsilyl)trifluoroacetamide (MTBSTFA) (4). 

A-Diketones In the presence of excess tin(ll) triflate and a base (N-trimethyl-silylimidazole), P-keto aryl sulfoxides (excess) react with silyl enol ethers to provide 2-arylsulfenyl-1,4-diketones in moderate to high yield. 

The silyl-Hilbert-Johnson method of nucleoside synthesis, using trimethylsilyltriflate as catalyst, is useful for the preparation of N-3 nucleosides (e.g., from 4-carbamoylimidazolium-5-olate) <84JHC529>, and a similar silyl displacement method has been used to make 1-alkylthio- and 1-phenylthio-l-trimethylsilyloxyalkanes and -cycloalkanes. This latter process uses 1-trimethyl-silylimidazole (177) and trimethylsilyltriflate as catalyst <84CHE662, 90S104>. The use of two equivalents of the thiol prevents the formation of imidazole adducts (Scheme 116) <90S104>. 

Where strength of silylating agent is the most important consideration, trimethyl-silylimidazole (TSIM) has been the reagent of choice. Another reagent which takes advantage of a nucleophilic group s ready displacement without formation of a... 

Acid-sensitive systems represent a particularly useful application for desilylative nitration with nitronium salts. Mononitration of imidazoles and triazoles is difficult because acid formed in the reactions even with NO2 BF4 tends to catalyze denitration. However, the nitration of tri-methylsilyl derivatives with NO2 BF overcomes this difficulty. It has been shown for 2-isopropyl-1-trimethyl-silylimidazole that it is possible to obtain its nitro compounds which could not be obtained previously (c.g., 2-isopropyl-1,4-dinitroimidazole) [149], Desilylative N-nitration is involved in the reaction. 

Derivatization with trimethyl-silylimidazole (TMSI) in pyridine and MSTFA... 

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