1-Trimethylsilyl imidazole

Figure 7.9 Structures of j-methacryloxypropyltrimethoxysilane (TMPS) (a), n-propyltrimethoxysilane (PTMS) (b), 3-isocyanatopropyltriethoxysilane (IPTES) (c), -(3,4, epoxycyclohexyOtrimethoxysilane (EETMS) (d), vinyltrimethoxysilane (VTMS) (e), 3-trimethylsilylpropanoic anhydride (f), 2-trimethylsilylmethylglutaric anhydride fg), trimethylsilylethenone (h) 1 -(trimethylsilyl)imidazole (i), N-(trimethylsilyl)acetamide (j) and 3-glycidoxypropyltrimethoxysilane (k).

Imidazole werden durch die gangigen Silylierungsreagentien wie z. B. Hexamethyl-disilazan 1-Trimethylsilyl-imidazol 85%)885 886 oder Chlorsilan/Base [l-Dimethyl-( 1,1,2-trimethyl-pro-pyl)-silyl-imidazol (mit Triethylamin als Base 76%)887 1-Trimethylsilyl-imidazol (aus Natrium-imidazolid mit Chlor-trimethyl-silan 95%)]792 in 1-Position silyliert. 

Der Trialkylsilyl-Rest aus Trichloressigsaure-trialkylsilylestern wird mit Kaliumcarbonat unter Phasentransfer-Katalyse ebenfalls auf Imidazole iibertragen. Nach dieser Methode lassen sich z.B. 1-Trimethylsilyl-imidazol (80%) und l-(tert -Butyl-dimethyl-silyl)-imidazol (75%) herstel-len887. 

Das kommerziell verfiigbare 1-Trimethylsilyl-imidazol (s.S. 109) ist ein sehr vielseitig verwend-bares Edukt zur Herstellung 1-substituierter Imidazole. 

Imidazole, l-(trimethylsilyl)- 1H-lmidazole, 1-(trimethylsilyl)- Imidazole, N-(trimethylsilyl)-. See Trimethylsilyl imidazole... 

Treatment of the sulfoxide 1222 a with tert-butyldimethylsilyl chloride 85 a and excess imidazole in DMF at 25 °C furnishes the imidazole derivative 1223a in 70% yield, whereas the phenyl derivative 1222b affords, besides 47% of 1223b , the cyclized product 1224 in 24% yield and 94 a and imidazole hydrochloride [34] (Scheme 8.14). Reaction of 1225 with N-(trimethylsilyl)imidazole 1219 at 170°C affords 1226 in 50% yield [35]. 

Imidazolium salts that can be prepared by the first procedure, the alkylation of imidazole, are easy to obtain and often used for metal complex synthesis. Potassium imidazolide is reacted with the first equivalent of alkyl halide in toluene to give the 1-alkylimidazole. Subsequent alkylation in 3-position is achieved by addition of another equivalent of alkyl halide [Eq. (2)]. " A variant of this approach employs commercially available A-trimethylsilyl imidazole with 2 equiv of an alkyl chloride, under elimination of volatile MesSiCl. The drawback of these simple routes is the fact that only primary alkyl halides can be reacted in satisfactory yields because secondary and tertiary alkyl halides give substantial amounts of elimination by-products. 

Disilathianes, for example (SiH3)2S and [(CH3)3Si] 2S, have been prepared by several routes, namely, the reaction of iodosilane with silver8 and mercuric2 sulfides halosilanes with lithium sulfide,7 [NH4]SH,9 and [Me3NH]SH7 disilaselenane with H2S10 and trisilylphosphine with sulfur.10 Recently, the synthesis of hexamethyldisilathiane, [(CH3)3Si] 2S, was described from the protolysis of l-(trimethylsilyl)imidazole with H2S and from the dehydrohalogen-ation of chlorotrimethylsilane and H2S with a tertiary amine.11 Both of these methods require about 18 hours. 

A powerful trimethylsilylating reagent, selective for hydroxyl groups, is N-(trimethylsilyl)imidazole (4) it is relatively tolerant to... 

N-(trimethylsilyl)imidazole, is particularly useful in the presence of water and reacts virtually quantitatively with glucose in 50% water solutions (75). Dimethylsilyl ethers generated from (CHj SiHCl have also been suggested and provide greater... 

A/-Trimethylsilyl diethylamine (TMSDEA) A/-Trimethylsilyl imidazole (TMSIM)... 

Silylation with silyl chlorides or silyl triflates is performed in the presence of auxiliary bases, e.g. pyridine, TEA, imidazole, etc., in solvents such as CH2CI2, CHQ3, DMF, or As milder reagents A-methyl-G-(trimethylsilyl)acetamide and preferably A,C)-bis(trimethylsilyl)acetamide (BTMSA, 136) (Scheme 72) are used for such purposes. Since the acetamide that results from this reaction is difficult to remove from the reaction medium, cyanotrimethylsilanet or l-(trimethylsilyl)imidazole (137).t l may be used as alternatives. For quantitative silylation of amino acids containing additional side-chain functionalities, excess silylating agent is required. 

Use. For glpc separation of catecholamines. Horning et at.1 converted these substances first into the trimethylsilyl ethers by reaction with trimethylsilyl-imidazole in acetonitrile acylation of primary and secondary groups was then effected by addition of N-heptafluorobutyrylimidazole. The resulting trimethylsilyl ether-heptafluorobutyryl (TMSi-HFB) derivatives were found to have excellent glpc properties.1... 

The reaction between l-(trimethylsilyl)imidazole and hydrogen sulfide may be effected either in a standard high-vacuum system or... 

Silyl derivatives have received much attention, they can be utilized to block diverse polar groups (OH, COOH, SH, NH2, =NH). The amino group is not very reactive in silylation reactions. Silyl derivatives are either trimethyl chlorosilanes (TMS), hexamethyldisilazane (HMDS) in conjunction with TMS, silylamines such as trhnethylsilyl diethylamine and trimethylsilyl imidazole, silyl amides such as A,(9-bistrimethylsilylfluoroacetamide (BSTTFA). Example is given by sterols. Isomers with a hydroxy group in the a position are not separated from the (S isomers but when the OH group is converted into a suitable derivative (e.g., TMS) both isomers are well resolved. 

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