Phenazines with rearrangement

In warm mineral acid, formazans (195) rearrange to a benzotriazine (196) eliminating an amine (Scheme 29).8,26 27 334 338 339 H owever, when R is methyl, phenylazo, or oxalyl, the main product is the phenazine 197 along with a trace amount of the benzotriazine.340 The mechanism of this reaction is not well understood.341 345... 

The authors propose the following mechanism (Scheme 47) The benzoxepine is protonated, yielding the enol. Subsequent proton transfer gives the unstable oxonium ion. Rearrangement via C—O bond cleavage and formation of a new C—C bond generates an aromatic compound, ethyl 3,4-dihydroxy-2-naphthoate. This intermediate then reacts with o-phenylenediamine to yield the respective phenazine. 

Reaction of chlorotriaryl derivatives with potassium diisopropylamide have been reported to give alkyl-shifted phenazine derivatives by either 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 (Scheme 193). ... 

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