Iodotrimethylsilanes, synthesis

Sakurai, H., Sasaki, K., Hosomi, A. Chemistry of organosiiicon compounds. 143. Regiospecific aiiyiation of acetals with aiiyisiianes catalyzed by iodotrimethylsilane. Synthesis of homoallylethers. Tetrahedron Lett. 1981, 22, 745-748. 

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. 

An illustrative example of the introduction of the benzyloxycarbonyl group, and its removal by hydrogenolysis is given in the synthesis of L-prolylglycine (Expt 5.188). An alternative reagent for the removal of this protecting group is iodotrimethylsilane in acetonitrile at room temperature.229... 

Deoxygenation of 1,4-endooxides.1 The transformation of a 1,4-endooxide (1) to the corresponding aromatic hydrocarbon (2) can be effected in high yield with iodotrimethylsilane. The deoxygenation was used for a novel synthesis of 1,4-di-methylphenanthrene (3) as shown in equation (I). 

Recent methods for the cleavage of allyl ethers that have that have yet to be tested on the anvil of complex target synthesis include (a) diborane generated in situ by reaction of sodium borohydride with iodine in THF at 0 °C (cyanoT ester, nitro, acetonide and tetrahydropyranyl groups survive) 434 (b) cerium(Ill) chloride and sodium iodide in refluxing acetonitrile (benzyl. THP and Boc groups survive) 435 (c) iodotrimethylsilane in acetonitrile at room temperature 436 and (d) DDO in wet dichloromethane (secondary allyl ethers, benzyl, acetate and TBS groups survive).437... 

Allylsilane 59 was obtained by initial reaction of the succinimide 55 with the corresponding Grig-nard alkylsilane and a subsequent simple sequence of reactions. This allylsilane was readily cyclized in formic acid at room temperature to 60, which was subjected to a Wacker oxidation (Tsuji 1984) to afford the dihydroanatoxin-a derivative 28. The nitrogen deprotection step with iodotrimethylsilane (Melching et al. 1986) funushedthe ( )-dihydroanatoxin-a, which was reprotected with oc according to the previously discussed Rapoport methodology (Sardina et al. 1989) to furnish the racemic ( )-anatoxin-a. The overall yield of this synthesis was 7% from the succinimide. 

Sabitha, G., Reddy, G. S. K. K., Reddy, C. S., Yadav, J. S. One-pot synthesis of dihydropyrimidinones using iodotrimethylsilane. Facile and new improved protocol for the Biginelli reaction at room temperature. Synlett 2003, 858-860. 

This methodology can also be applied to the synthesis of heterocycles. Thus, the rearrangement of 4 a or 4b, derived from (S )-alanine or (S )-valine using the premixed method (see p 3468)615, gives 5 a or 5 b as single diastereomers which, after deprotection with iodotrimethylsilane in chloroform, afford pyrrolidine derivatives 6329. 

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... 

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