Lithium compounds phase effects

The reactions of dimethyl methylphosphonate and the corresponding carbanion in the gas phase have been investigated. The carbanion displays a similar range of reactions to those encountered in solution, including olefmation with carbonyl compounds. The effect on olefin stereochemistry of a variety of conditions in reactions of a-phosphono lactones (e.g. 129) with ethanal and propanal has been studied and the results applied in syntheses of integerrinecic acid and senecic acid lactones. Yet further minor modifications of the conditions for phosphonate-olefination reactions, involving the use of lithium hydroxide as the base, have been reported. ... 

The effects of different alkali-metal cations on the vapour-phase fluorination of benzene with the complex fluorides M+CoFi" have been described. An appreciable proportion of the product from CSC0F4 at 250 °C consists of aromatic compounds, including hexafluoro- (4%) and pentafluoro-benzene(9%). The lithium compound yields mainly 3,3,6,6-tetrafluorocyclo-hexa-1,4-diene, but the sodium and rubidium salts have no particular advantages over the potassium compound described previously. The results obtained from the reaction of 1,3-bistrifluoromethylbenzene with KC0F4,... 

Modulation of second-messenger pathways is also an attractive target upon which to base novel antidepressants. Rolipram [61413-54-5] an antidepressant in the preregistration phase, enhances the effects of noradrenaline though selective inhibition of central phosphodiesterase, an enzyme which degrades cycHc adenosiae monophosphate (cAMP). Modulation of the phosphatidyl iaositol second-messenger system coupled to, for example, 5-HT,, 5-HT,3, or 5-HT2( receptors might also lead to novel antidepressants, as well as to alternatives to lithium for treatment of mania. Novel compounds such as inhibitors of A-adenosyl-methionine or central catechol-0-methyltransferase also warrant attention. 

The most comprehensive study of lithium cation basicities for organic bases was conducted by Taft, Gal and coworkers who investigated the effect of molecular structure on the gas-phase cation and proton basicities. Taft s LCA scale was revised and extended, and the lithium cation basicity scale now includes over 200 compounds. In the same work the correlations between gas-phase basicities toward lithium cation (LCB) and proton (GB) were examined. Good correlations are obtained provided that separate lines are drawn for homogeneous families and the differences in slopes are traced back to the different sensitivities to structural effects. Large deviations are explained by either a different attachment center for Li+ and H+ or a chelation effect toward Li+. Figure 5 describes three types of interactions that involve chelation of a lithium cation. 

Highlights in the chemistry of cyclopentadienyl compounds have been reviewed.65 Trends in the metallation energies of the gas-phase cyclopentadienyl and methyl compounds of the alkali metals have been studied by ab initio pseudopotential calculations. Whereas there is a smooth increase in polarity of M-(C5H5) bonds from Li to Cs, lithium appears to be less electronegative than sodium in methyl derivatives. The difference between C5H5 and CH3 derivatives is attributed to differences in covalent contributions to the M-C bonds. In solution or in the solid state these trends may be masked by the effects of solvation or crystal packing.66 The interaction between the alkali metal ions Li+-K+ and benzene has also been discussed.67... 

Alkali metal nitride chemistry is effectively confined to that of lithium and sodium [2], and dominated by lithium nitride, Li3N, a compound that has long fascinated solid-state chemists since early reports of its synthesis and characterisation [3-5]. In the ternary phase system, Li-N-H, lithium also forms three stoichiometric ternary hydrogen-containing compounds, the imide, Li2NH, the amide, LiNH2, and the nitride hydride, Li4NH. The first... 

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