Substituent effects meta-benzynes

The preferred site of addition of amide ion to substituted benzynes is considered to be that giving the aryl anion which is most stabilised by the inductive effect of the substituent. With 3-substituted benzynes, amide ion would thus be expected to add preferentially to the meta 3 ... 

Transposition of substituents takes place from aromatic compounds based on ortho effects from hydroxyphenyl ketones via assumed nucleophilic attack on the carbonyl carbon atom of the phenoxide site to give a tight tetravalent intermediate that promptly decomposes through benzyne neutral release and formation of a carboxylate anion (Scheme 17.19a). This reaction is hindered from meta- and para-substituted phenols. Alternatively, radical alkane loss is also observed that can be rationalized by considering the formation of an ion-neutral complex (Scheme 17.19b) comprised of quinone-like and alkylide groups. The relatively low ionization energy allows the generation of odd-electron quinone-like species and the elimination of the alkane radical (Scheme 17.19b). 

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