Reductions iodotrimethylsilane

Iodotrimethylsilane generated in situ from chlorotrimetylsilane and sodium iodide effects the reduction of nitroalkenes into ketones at 0 °C. This method is useful for the conversion of nitro steroids or nitro terpenoids to the corresponding ketones (Eq. 6.24).43... 

Botta and coworkers recently developed an Oxone cleavage methodology for the solid-phase synthesis of substituted uracils (equation 57)165. Whereas some common methods of thioether cleavage, such as reduction with Na/NH3, acid catalyzed hydrolysis, heavy metal ions followed by treatment with hydrogen sulfide and iodotrimethylsilane proved to be unsuccessful for this reduction, Oxone was shown to be an efficient and selective reagent for cleavage of polymer bound thiouracils. 

Few examples of intramolecular enol silyl ether or silyl ketene acetal cyclizations to oc,3-enones have been reported. Notable, as exemplified in Scheme 34, is the iodotrimethylsilane-mediated intramolecular cyclization of 5-(iodoacetoxy)-a,3-enones (211) to 5-lactones (214). These cyclizations proceed with in situ generated silyl ketene acetals (212) arising from iodotrimethylsilane reduction of the iodoacetoxy moiety.87... 

Thus two successive oxidations of 429 (Scheme 59) involving the Jones reagent and dichlorodicyano-p-benzoquinone respectively led to the enone 430. A similar reductive cleavage as above of the derived dimethyl acetal 431 with diisobutylaluminium hydride occurred from the less hindered a-side to furnish the P-methoxyether 432 as the major isomer. Selective O-debenzylation of432, achieved with iodotrimethylsilane led to ( )-coccinine (413). 

A novel synthetic method for the preparation of two cytotoxic furonaphthoquinones 5a,b was reported. Regjospecific metallation of 3-furoic acid (3) at the 2-position using LDA at -78°C and subsequent treatment with the corresponding aldehydes ( R = H, OMe) affords the acids 4 (X = OH) which after reduction (to 4b with iodotrimethylsilane) and ring closure (Friedel-Crafts) were transformed to 5a,b <95JCS(P1)1085>. 

Furans are obtained a.s side-products during iodotrimethylsilane reduction of benzoins or by elimination of water after hemiacetal formation. Perlluoro(tetramethylfuran) 22 is synthesized by an unusual sequence starting from ketenimine 20. Treatment with 3-chloro-peroxybenzoic acid gives ketone 21, a compound that in an assumed radical process reacts W ith 0.6 equivalents of bromine at 250 C in a Pyrex ampule to form furan 22 in 95% yield. 

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. 

A number of reviews which relate to reduction in general and only in part to the types of reduction presently being considered may also be of interest to the reader. These include a review of hydride reductions in general by Brown and Krishnamurthy and of metal alkoxyaluminum hydrides in particular by Malek. ° The important role of electrophilic catalysis in achieving reductive S—O bond cleavage is summarized in a review of the applications of iodotrimethylsilane by Olah and Narang. ... 

A neat four-step synthesis of the triquinane sesquiterpene hirsutene (4) has been described, which features the novel iodotrimethylsilane induced rearrangement of the dione (1), to (2), as a key step. Reductive methylation of the enone (2) to (3),followed by Wittig methylenation then completed the synthesis. ... 

Although a number of syntheses of the angular triquinane sesquiterpene isocomene (18) have now been published, the synthesis by Dreiding et al. is interesting since it features the sequential alkynone cyclisations (14)— -(15) and (16)——(17) as the two key 5-ring annulation reactions. In a new synthesis of the related sesquiterpene silphinene (23) intramolecular(2+2] photocycloaddition from (19) is first used to elaborate the tricycle (20), which on brief exposure to iodotrimethylsilane produces (21). Reduction of (21) to (22), and functional group elaboration then completed the... 

The authors adapted this methodology to prepare 3,3,3-trifluoroalanine 220. Benzamide was first converted to 217 (Ar = CgHs) followed by reductive cyclization to 5-fluoro-2-phenyl-4-(trifluoromethyl)oxazole 218 (Ar = C6H5). Displacement of fluoride in 218 gave 5-ethoxy-2-phenyl-4-(trifluoromethyl)oxazole 219, which was converted to 220 with iodotrimethylsilane (Scheme 1.61). 

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