Directed metalation aromatic compounds

Directed lithiation of aromatic compounds is a reaction of broad scope and considerable synthetic utility. The metalation of arenesulfonyl systems was first observed by Gilman and Webb and by Truce and Amos who reported that diphenyl sulfone is easily metalated at an orf/io-position by butyllithium. Subsequently, in 1958, Truce and coworkers discovered that metalation of mesityl phenyl sulfone (110) occurred entirely at an orf/io-methyl group and not at a ring carbon, as expected. Furthermore, refluxing an ether solution of the lithiated species resulted in a novel and unusual variation of the Smiles rearrangement and formation of 2-benzyl-4,6-dimethyl-benzenesulfinic acid (111) in almost quatitative yield (equation 78). Several other o-methyl diaryl sulfones have also been shown to rearrange to o-benzylbenzenesulfinic acids when heated in ether solution with... 

Silicon linker 76 was used for direct loading of aromatic compounds to supports for the assembly of pyridine-based tricyclics (Scheme 39) [87], Following the initial coupling of an aromatic bromide to the resin by halogen/metal exchange in the presence of tert-butyl lithium, a... 

Directed metallation of aromatic compounds TABLE 2. piTa and ortholithiation ... 

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