Nucleophilic substitution—continued ring nitrogens, influence

Aryl and heteroaryl azides are known to undergo ring expansion to azepines on photoelimination of nitrogen in the presence of nucleophiles. Evidence for benzazirine and 1-azacycloheptatetraene intermediates has previously been described and both species continue to be invoked to explain transformations of this type. The presence and nature of substituents appears to influence the course of the reaction, with electron-withdrawing substituents promoting azepine formation. o-Substituted aryl azides (102) are converted on irradiation in methanol-tetrahydrofuran into the 3-substituted 2-methoxy-3H-azepines (103). A pathway via the benzazirine (104) is proposed in Scheme 4, although... 

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