= Solution
Amide base removes a proton alpha to the <nitrile>, giving a resonance-stabilized <carbon> <nucleophile>. Removal of the available aryl proton ortho to <chlorine>, together with <chloride> elimination, generates a <benzyne> between the chlorine-bearing <carbon> and its unsubstituted ortho neighbour. The side-chain <nitrile> carbanion attacks the former chlorine-bearing aryne <carbon> intramolecularly; one aryne pi bond shifts to the neighbouring aryl <carbon>. Protonation of that aryl anion by ammonia restores the aromatic ring. The newly formed C–C bond closes the \b[four-membered ring of the cyanobenzocyclobutane product]. Two deprotonation processes are required to generate both the <nitrile> <nucleophile> and the aryne. The <nitrile> group is retained, and the product is not formed by simple replacement of aryl <chlorine> with an external amide <nucleophile>.
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