Iodotrimethylsilane, reaction with

Alkyl esters are efficiently dealkylated to trimethylsilyl esters with high concentrations of iodotrimethylsilane either in chloroform or sulfolane solutions at 25-80° or without solvent at 100-110°.Hydrolysis of the trimethylsilyl esters serves to release the carboxylic acid. Amines may be recovered from O-methyl, O-ethyl, and O-benzyl carbamates after reaction with iodotrimethylsilane in chloroform or sulfolane at 50—60° and subsequent methanolysis. The conversion of dimethyl, diethyl, and ethylene acetals and ketals to the parent aldehydes and ketones under aprotic conditions has been accomplished with this reagent. The reactions of alcohols (or the corresponding trimethylsilyl ethers) and aldehydes with iodotrimethylsilane give alkyl iodides and a-iodosilyl ethers,respectively. lodomethyl methyl ether is obtained from cleavage of dimethoxymethane with iodotrimethylsilane. 

The use of iodotrimethylsilane for this purpose provides an effective alternative to known methods. Thus the reaction of primary and secondary methyl ethers with iodotrimethylsilane in chloroform or acetonitrile at 25—60° for 2—64 hours affords the corresponding trimethylsilyl ethers in high yield. The alcohols may be liberated from the trimethylsilyl ethers by methanolysis. The mechanism of the ether cleavage is presumed to involve initial formation of a trimethylsilyl oxonium ion which is converted to the silyl ether by nucleophilic attack of iodide at the methyl group. tert-Butyl, trityl, and benzyl ethers of primary and secondary alcohols are rapidly converted to trimethylsilyl ethers by the action of iodotrimethylsilane, probably via heterolysis of silyl oxonium ion intermediates. The cleavage of aryl methyl ethers to aryl trimethylsilyl ethers may also be effected more slowly by reaction with iodotrimethylsilane at 25—50° in chloroform or sulfolane for 12-125 hours, with iodotrimethylsilane at 100—110° in the absence of solvent, " and with iodotrimethylsilane generated in situ from iodine and trimcthylphenylsilane at 100°. ... 

Halosilanes are also potent halogen donors, particularly in exchange reactions with alkyl fluorides, due to the strong Si-F bond formation. Tertiary- and secondary-alkyl fluorides are reacted with iodotrimethylsilane to yield alkyl iodides in high yields (equation 19)214 ... 

C-Allylated glycopyranosides.4 a-Glycopyranosides or a-glycopyranosyl chlorides are converted stereoselectively into a-C-allylated glycopyranosides on reaction with al-lylsilanes catalyzed by trimethylsilyl triflate. Iodotrimethylsilane is less effective as the catalyst. 

Reduction of oi-ketols. a-Ketols are deoxygenated to the corresponding ketones in 75-95% yield by reaction with 2.5 equiv. of iodotrimethylsilane inCHCb or CH2CI2 at room temperature. 

Optically active thiazolidine -oxides (259) undergo the silicon Pummerer reaction with t-butyldimethylsilyl trifluoromethanesulfonate or iodotrimethylsilane <87TL5903>. When the former is used as silylating agent, thiazolidines (260) and 4-thiazolines (261) are obtained. With iodotrimethylsilane, the iodothiazolidines (262) and the dihydro-1,4-thiazine (263) are obtained (Scheme 65). 

Ester Cleavage. Although esters are readily cleaved with iodotrimethylsilane, reaction of esters with TMS-Br under similar conditions gives somewhat lower yields of silyl esters or acids upon hydrolysis (eq 4). Lactones, however, react with TMS-Br at 100 °C to afford < >-bromocarboxylic acids after hydrolysis of the silyl ester (eq 5). ... 

If no aqueous workup, but anhydrous cleavage of the reaction product 11 is performed with iodotrimethylsilane, the titanium iodide 12 can be recovered or used again in the same flask36. 

The structurally simplest silicon reagent that has been used to reduce sulphoxides is the carbene analog, dimethylsilylene (Me2Si )29. This molecule was used as a mechanistic probe and did not appear to be useful synthetically. Other silanes that have been used to reduce sulphoxides include iodotrimethylsilane, which is selective but unstable, and chlorotrimethylsilane in the presence of sodium iodide, which is easy to use, but is unselective since it cleaves esters, lactones and ethers it also converts alcohols into iodides. To circumvent these complications, Olah30 has developed the use of methyltrichlorosilane, again in the presence of sodium iodide, in dry acetonitrile (equation 8). A standard range of sulphoxides was reduced under mild conditions, with yields between 80 and 95% and with a simple workup process. The mechanism for the reaction is probably very similar to that given in equation (6), if the tricoordinate boron atoms in this reaction scheme are replaced... 

Dialkyl and alkyl aryl ethers can be cleaved with iodotrimethylsilane ROR -bMe3SiI — Rl-bMe3SiOR. A more convenient and less exjjensive alternative, which gives the same products, is a mixture of chlorotrimethylsilane and Nal. Alkyl aryl ethers can also be cleaved with Lil to give alkyl iodides and salts of phenols in a reaction similar to 10-73. Triphenyldibromophosphorane (Ph3PBr2) cleaves dialkyl ethers to give 2mol of alkyl bromide. ... 

Iodotrimethylsilane formed in situ from the reaction of chlorotrimethylsilane and sodium iodide, also effects the conversion of 2-ene-l,4-diols to 1,3-dienes (equation 16)46. Allylic thionocarbonates on heating with triphenylphosphite undergo deoxygenation (Corey-Winter reaction) to generate olefins47. This procedure has been used for making hexatrienes (equation 17)47b. 

To 2,3-dioleoyloxy-l-iodopropane (3.65 g, 5 mmol) was added tris(tri-methylsilyl) phosphite (15.05 g, 50 mmol), along with a trace of butyl hydrogen phthalate. The reaction mixture was stirred under a static nitrogen atmosphere with heating at 125°C for 16 h. After this time, excess tris(trimethylsilyl) phosphite and iodotrimethylsilane were removed by high vacuum distillation (bath 100°C) to leave a colorless oil. The residue was dissolved in THF water (9 1, 50 ml) and allowed to stand in the dark at room temperature for 12 h. The solvent was... 

Iodosilane has been prepared by the cleavage of phenylsilane10 or chloro-phenylsilane11,12 with hydrogen iodide, and by the reaction of monosilane with hydrogen iodide in the presence of a catalytic amount of aluminum triiodide.4 The latter method has been extended to prepare the methylated iodosilanes.5,13 Iodotrimethylsilane has also been prepared by the cleavage of trimethylphenyl-silane with iodine.14... 

In the presence of proton and/or Lewis acid and strong nucleophiles bicyclo[3.2.0]heptan-6-ones are converted to 3-substituted cycloheptanones (Table 15). Bicyclo[3.2.0]heptan-6-ones rearrange to give 3-iodocycloheptanones on treatment with iodotrimethylsilane. Zinc(II) iodide or mercury(II) halides as catalysts enhance the rate and the selectivity of the reaction.31 If a second, enolizable carbonyl group is present, an intramolecular alkylation may follow the ring enlargement under these reaction conditions.32 Consecutive treatment with tributyltin hydride/ 2,2 -azobisisobutyronitrile affords reduced, iodo-free cycloheptanones, whilst treatment with l,8-diazabicyclo[5.4.0]undecene yields cycloheptenones.33 Similarly, benzenethiol adds to the central bond of bicyclo[3.2.0]heptan-6-ones in the presence of zinc(II) chloride and hydrochloric acid under anhydrous conditions to form 3-(phenylsulfanyl)cycloheptanones.34... 

Compared to 51, the reaction of THF with iodotrimethylsilane requires a more prolonged time and takes place at a higher temperature (60°C)317. 

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