Master Organic Chemistry Reaction Guide

Nucleophilic Aromatic Substitution Via Arynes

Description: Treatment of an aromatic containing a good leaving group with a strong base will lead to formation of an “aryne”. Attack of the aryne with a nucleophile then results in a product which is formally the result of nucleophilic aromatic substitution.


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Real-Life Examples:

Org. Synth. 1959, 39, 75

DOI Link: 10.15227/orgsyn.039.0075

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Org. Synth. 1966, 46, 107

DOI Link: 10.15227/orgsyn.046.0107

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3 thoughts on “Nucleophilic Aromatic Substitution Via Arynes

  1. Nucleophilic aromatic substitution via arynes (a.k.a. benzynes) does not seem to require electron-withdrawing groups ortho or para to the leaving group in order to activate it–why is that?

    1. The reason is that it goes through a different mechanism.

      It’s an elimination reaction, essentially. The strong base (NaNH2) breaks C-H on the ring which then leads to elimination of an adjacent leaving group (such as Br or Cl) forming the pseudo triple bond.

      None of the pi bonds in the aromatic ring are formed or broken.

      In nucleophilic aromatic substitution, a nucleophile attacks the ring and forms a new bond, breaking one of the pi bonds in the ring. The resulting negative charge is then stabilized by one of the electron withdrawing groups. Then the leaving group is expelled with restoration of aromaticity.

      Shorter version: in arene formation, aromaticity is never disrupted.

      Hope this helps! James

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