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Metal substitution, effect aggregation

Methoxy-substituted aromatic compound 4 is lithiated metalation with Buli in THF, a step in which it proves useful to include lithium chloride. Because of the greater basicity of /t-butyllithium relative to 4. direct metallation is in fact possible thermodynamically, but /i-butyllithium is generally present in solution as a tetra-mer, and this reduces its reactivity. Addition of lithium chloride destroys these aggregates, and that eliminates the kinetic inhibition. Lithiated aromatic species 18 is further stabilized through chelate formation between lithium and the orr/icr-methoxy groups (ortho effect).8... [Pg.18]

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See also in sourсe #XX -- [ Pg.631 ]



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