On the photochemistry of 4-azidoquinoline 1-oxide: Structural elucidation of primary photoproduct

The primary product of the photolysis of 4-azidoquinoline 1-oxide (1) is believed to be the azo-dimer (4), consistent with the photochemistry of the pyridine analogue (2). This species has not been unambiguously identified, and previous workers have only isolated various isomers of the azoxy species (5). A combined IR, NMR, LC/MS and computational study confirms the structure 4 as the primary product of photolysis of 1 at 355 nm, suggesting that 5 arises from secondary photochemistry of 4.

► 4-Azidoquinoline 1-oxide (1) undergoes photolysis to generate a triplet nitrene.
► The primary photoproduct of this reaction had yet to be unambiguously identified.
► The primary photoproduct was identified as the azoarene 4 by NMR, IR and MS.
► Structural and spectral data were supported by DFT calculations.
► The previously reported azoxy compound (5) is a secondary photoproduct.