Aryl anions aryne generation

A variety of substituted aromatic compounds have been prepared through addition of anionic nucleophiles to arynes generated from readily accessible precursors.1 Most of the laboratory preparations start with aryl halides. The coupling yields are usually good to modest (equations 13-15) but can be poor (equation 16).83 Sometimes, a dramatic improvement in reaction efficiency can be achieved by the change of the base/solvent pair or other reaction conditions. For instance, in arylation of phenoxides and benzenethiolates, a switch over to DMSO as the solvent boosted the yield considerably (equation 17).86 Another example, illustrative of this point, is the reaction of N-methylpyrrolidone with aryl halides where an acceptable yield could not be obtained under a variety of conditions except with LICA in THF (equation 18).71... 

More remarkable are the reactions between ketone enolate ions and arynes generated by a complex base. Products derived using the aprotic solvent system differ considerably from those involving enolate ions in ammonia. In the protic solvent the aryl anion resulting from the addition of an enolate ion to an aryne is protonated and continued reaction is thereby prevented. Such protonation does not occur in the aprotic medium further reactions occur by intramolecular addition of the aryl anion to a carbonyl group, Scheme 5. Products obtained from acyclic ketones include... 

Table 1. Generation of Arynes via Aryl Anion Intermediates...

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