Apparent Alkyl Transfer and Phenazine Formation via an Aryne Intermediate

Treatment of chlorotriaryl derivatives 3a and 3d or fluorotriaryl derivatives 3b and 3e with potassium diisopropylamide afforded
alkyl-shifted
phenazine derivatives 5a/5b, rather than
the expected 9-membered triazaorthocyclophane 2a. The
phenazine derivatives were isolated in 78–98% yield depending
on the halogen and alkyl group present. In the absence of the halogen
(chloro or fluoro), the apparent alkyl shift proceeds more slowly
and cannot proceed via the intermediacy of the aryne intermediate.
Mechanistic possibilities include intramolecular nucleophilic attack
on an aryne intermediate leading to a zwitterionic intermediate and
alkyl transfer via a 5-endo-tet process, or via a
Smiles rearrangement.