Bromomethyldimethylsilyl deriv

Phenolic and acidic pesticides and herbicides were chromatographed as chloromethyl and bromomethyldimethylsilyl derivatives [502] and the entire procedure was applied to the analysis of these substances in soil, as follows. A 1-ml volume of n-hexane, 0.075 ml of dimethylamine and 0.09 ml of halomethyldimethylchlorosilane were mixed in a 5-ml vial, which was then closed and shaken vigorously. The mixture was centrifuged and 0.4 ml of the supernatant was transferred into an 8-ml test tube and 0.1 ml of ethyl acetate containing 100 jug of the substrate was added. The contents were refluxed for 30 min at 65°C, cooled and the reflux condenser was rinsed with 0.5 ml of n-hexane. 

Finally, via a cyclization reaction, disilacyclopentane derivatives can be formed. Thus, l-(bromodimethylsilyl)-2-(bromomethyldimethylsilyl)ethane (345) in the presence of lithium is converted to l,l,3,3-tetramethyl-l,3-disilacyclopentane (-disilolane) (346) (equation 157)181. 

Radical cyclization has also proved to be a useful tool for the Shishido group in their syntheses of triptoquinones B and C and triptocallol.40 Triptoquinone B and C have been shown to exhibit inhibitory activity on interleukin-1 and are both candidates for the treatment of rheumatoid arthritis. Shishido has accomplished synthesis of all three of these compounds, implementing the radical cyclization of bromomethyldimethylsilyl ether 39, derived from optically enriched alcohol 38, to give 40. Finally, the Tamao-Kumada oxidation step provides the natural product, triptocallol (41). 

Preparation of the IDMS ether derivatives of steroids The silylating reagent was prepared from hexane (2 ml), bromomethyldimethylsilyl chloride (200 jui) and diethylamine (100 pi). Portions of the reagent (100 pi) were added to authentic steroids (nanogram amounts) or plasma extracts and allowed to stand at room temperature for 45 min. After removal of the excess reagent under a stream of nitrogen, 100 pi of a saturated sodium iodide solution in acetone was added and the mixture was heated at 37 °C for 30 min. The reaction mixture was blown to dryness and the residue was dissolved in 0.5 ml of a mixture of hexane/dichloromethane/ethanol/acetone (55 44 0.5v/v/v/v). The mixture was applied to a column of alumina (3 g, 200 mm x 6 mm) which was eluted with 7 ml of the same solvent the derivatives emerged in the second 3.5 ml of eluent. After evaporation of the solvent, the steroid derivatives were dissolved in hexane (100 pi) for analysis by GC and GC-MS. 

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