Lithium complexing agent, effects

Wang GM, van Beylen M (2003) Influence of 7t-complexing agents on the anionic polymerization of styrene with lithium as counterion in cyclohexane. 1. Effect of durene. Polymer 44 6205-6210... 

Finally one particular problem of alkali ion complex specificity of enormous medical relevance should be mentioned, i.e. the finding that lithium is very effective as a psychoactive agent in the treatment of manic-depressive disorders. This finding, first made by Cade320 in 1949, and systematically investigated by Schou and his coworkers321 has stimulated many studies of biological effects of lithium. 

Reversal correlates with the presence of lithium ion and also with the involvement of betaine species. These two risk factors are interrelated because lithium halides rapidly cleave oxaphosphetane 31 or 32 (Scheme 8) at — 70°C resulting in the reversible formation of the betaine lithium halide complexes 40 or 41, respectively (18b). Donor solvents shift the equilibrium toward the oxaphosphetane by coordinating the lithium halides and thereby promote stereospecific decomposition to the alkenes. If the solvent is not an effective lithium coordinating agent, then 40 and 41 decompose slowly, and the risk of... 

One of the general features of the reactivity of enolate anions is the sensitivity of both the reaction rate and the ratio of C- versus O-alkylation to the degree of aggregation of the enolate. For example, addition of HMPA frequently increases the rate of enolate alkylation reactions. Use of dipolar aprotic solvents such as DMF and DMSO in place of the THF also leads to rate acceleration. These effects can be attributed, at least in part, to dissociation of the lithium enolate aggregates. Similar effects are observed when crown ethers or similar cation-complexing agents are added to reaction mixtures. 

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