Reagents trimethylsilyl iodide

A neat, one-pot method for the preparation of the activated N -BOC-a-amino-acid esters (169) directly from a-amino-acids niakes further use (c/. 1, 200) of the thiophen derivative (168) (Scheme 53). " An apparently simple way to remove both N -benzyloxy- and t-butyloxy-carbonyl groups from peptides is to use the much publicized reagent trimethylsilyl iodide. ... 

Trimethylsilyl iodide [16029-98-4] (TMSI) is an effective reagent for cleaving esters and ethers. The reaction of hexamethyldisilane [1450-14-2] with iodine gives quantitative conversion to TMSI. A simple mixture of trimethylchlorosilane and sodium iodide can be used in a similar way to cleave esters and ethers (8), giving silylated acids or alcohols that can be Hberated by reaction with water. 

Me3SiCH2CH=CH2i TsOH, CH3CN, 70-80°, 1-2 h, 90-95% yield. This silylating reagent is stable to moisture. Allylsilanes can be used to protect alcohols, phenols, and carboxylic acids there is no reaction with thiophenol except when CF3S03H is used as a catalyst. The method is also applicable to the formation of r-butyldimethylsilyl derivatives the silyl ether of cyclohexanol was prepared in 95% yield from allyl-/-butyldi-methylsilane. Iodine, bromine, trimethylsilyl bromide, and trimethylsilyl iodide have also been used as catalysts. Nafion-H has been shown to be an effective catalyst. 

The direction of cleavage in unsymmetrical ethers is determined by the relative ease of O-R bond breaking by either SN2 (methyl, benzyl) or SW1 (r-butyl) processes. As trimethylsilyl iodide is rather expensive, alternative procedures that generate the reagent in situ have been devised. 

CH2=NMe2 I).21 A recent convenient preparation of the dimethyl-(methylene)ammonium iodide reagent from trimethylsilyl iodide and N,/V,/V, ZV -tetramethylenediamine22 could result in greater value in future being placed on this reaction for the preparation of terminal alkenes. 

Ketoximes may be rearranged directly to amides under a wide variety of conditicms. Phosphorus pen-tachloride, phosphorus oxychloride, thionyl chloride, trimethylsilyl iodide (TMS-I), formic acid, poly-phosphoric acid, trimethylsilyl polyphosphate and mineral acids have all been successfully employed. Representative procedures using these and other reagent systems have been documented previously. - ... 

Organophosphorus reagents based on triphenylphosphine, or trimethylsilyl iodide, may be used to deoxygenate epoxides to re-form the parent alkene. Reactions based on this, or on a related scheme using the reduction of an iodohydrin, have been used in the synthesis and protection of alkenes as their epoxides (Scheme 2.23). 

Trimethylsilyl iodide Trimethylsilyl triflate Hydrocarbons, halogenated, MeCN Hydrocarbons, halogenated Strong, used to deave ethers, acetals, esters Strong, used with silylated reagents... 

Takai and coworkers have recently reported their fmdings on the addition of y-alkoxyallylic chromium compounds to aldehydes. The reagents, which were generated by the reduction of dialkyl acetals (149) with C1CI2 in the presence of trimethylsilyl iodide, added to aldehydes (150) to produce vicinal diols... 

Trimethylsilyl iodide converts alcohols to iodides. The disadvantage of this method is the expensive reagent, which is avoided if trimethylsilyl chloride and sodium iodide are used instead (equation 27). Trimethylsilyl polyphosphate (PPSE), which is prepared from hexamethyldisiloxane and phosphorus pentoxide, also activates alcoholic hydroxy groups for substitutions with iodide anions (equation 28). ... 

Ethers are cleaved by HI faster than by HBr and HCl (Scheme 25). To prevent the undesirable reducing action of the reagent, KI and phosphoric or polyphosphoric acid are used to generate HI in situ (equation 32). The ether nd is also cleaved by trimethylsilyl iodide (equation 33). ... 

Although imidoyl iodides are chemically labile, their in situ generation from oxime derivatives with trimethylsilyl iodide or diethylaluminum iodide has been ascertained spectroscopically (equation 14). The synthetic utility of these reactive species has been demonstrated by further reacting them with external nucleophiles such as thiolates or Grignard reagents. For example, the imidoyl iodide (28), generated from acetophenone oxime carbonate with trimethylsilyl iodide, is further transformed to ethylthioimidate (29) and a-alkylated amine (30), respectively (Scheme 1 and equation 15). 

Aldoxime fragmentation is a well-known process for nitrile synthesis, and numerous reagents have been developed for this purpose. Trimethylsilyl iodide was recently found to be effective as a dehydration agent.2 ... 

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