A new bicyclic oxazaborines with a bridged nitrogen atom, their thermic rearrangement and fluorescence properties

Cyclic β-enaminones bearing secondary amino group react with 4-substituted benzenediazonium tetraphenylborates in dichloromethane to form substituted bicyclic [1,3,2λ4]oxazaborines The oxazaborines rearrange, on heating to 200 °C in the absence of solvent or in DMF or DMSO, to isomeric 2H-[1,2,4,3λ4]triazaborines. Previously prepared [1,3,2λ4]oxazaborines derived from acyclic β-enaminones bearing secondary amino group either did not undergo the rearrangement or with a lot of difficulties and with negligible yield. The fluorescence behaviour of the prepared triazaborines was observed. These compounds fluoresce in 2-methyltetrahydrofurane and in solid state under low temperatures.