Birch Reduction With Electron Withdrawing Substituents
In contrast to the examples with electron donating substituents, the case with withdrawing groups is more readily obvious. Thus, as depicted below, the structure of the penultimate dianion D is characterized by its being subject to trapping by alkyl halides.
Mechanism of reduction of benzoic acids, including possible alkylation
This dianion results independent of whether alcohol is used in the reduction or not. Thus the initial protonation by t-butyl alcohol or ammonia is para rather than ipso as seen in the step from B to C.
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