Lithium specific derivatives

Lithium is a soft, silvery alkali metal and has the lowest density of any metal. The word lithium is derived from lithos (Greek for stone ). Johan A. Arfredson discovered lithinm in Stockholm, Sweden, in 1817. Hnmphry Davy isolated it via electrolysis in 1818. Currently, lithinm metal is generated by the electrolysis of a molten mixture of lithium chloride, LiCl, and potassium chloride, KCl. In natnre it is never found in its elemental form. Its main sources are the minerals spodumene, petalite, lepidolite, and am-blygonite. Lithium s average crustal abundance is about 18 ppm. It has the highest specific heat of any solid element and is the least reactive alkali metal toward water. Lithium bums crimson in the flame test. 

Individual polyethers exhibit varying specificities for cations. Some polyethers have found appHcation as components in ion-selective electrodes for use in clinical medicine or in laboratory studies involving transport studies or measurement of transmembrane electrical potential (4). The methyl ester of monensin [28636-21 -7] i2ls been incorporated into a membrane sHde assembly used for the assay of semm sodium (see Biosensors) (5). Studies directed toward the design of a lithium selective electrode resulted in the synthesis of a derivative of monensin lactone that is highly specific for lithium (6). 

Halogen exchange with metallic derivatives provides a powerful means of introducing iodine into specific quinoline sites. It has proved possible to prepare 2-, 3-, and 4-iodoquinolines from the trimethylstannyl [82H(19)168] or lithium derivatives [86S670]. Protected 2-aminoquinoline, lithiated at C-3, was quenched with iodine to give a 90% yield of the 3-iodo derivative (86S670). 

This technique was used to synthesize some cyclohexane derivatives by substitution with electrophiles specifically in the axial or equatorial position. Whereas alkylation with dimethyl sulfate occurred smoothly, alkylation with haloalkanes failed completely. Rather nonstereoselective protonation of the lithium compound, as well as dehydrogenation to enol ethers, occurred. Operation of single electron transfer processes are believed to account for these results27. 

A variety of medical conditions cause water retention as the result of ADH excess. Unfortunately, specific ADH antagonists are available only for investigational purposes. Two nonselective agents, lithium and demeclocycline (a tetracycline derivative), are of limited use in some situations. 

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