The metal-free reactions of 2H-azirines with C,N-cyclic azomethine imines were investigated. N-Bridged strained ring-fused triazole derivatives or 1,2,4-triazine derivatives are obtained, and the chemoselectivity is dependent on the protecting group on the azomethine dipole. Although benzoyl-protected starting materials give access to strained polycyclic compounds, a ring-opening occurs in the case of a tosyl protecting group that is cleaved during the process with elimination of sulfinic acid. 1,2,4-Triazine can be prepared on a mmol-scale and concomitantly oxidized with air as an oxidant to form the corresponding ketone, which is an interesting structural motif that can be found in bioactive scaffolds.
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