DBU mediated one-pot synthesis of triazolo triazines via Dimroth type rearrangement.

Herein we report an efficient one-pot synthesis of [1,2,4]triazolo[1,5 a ][1,3,5]triazines from commercially available substituted aryl/heteroaryl aldehydes and substituted 2-hydrazinyl-1,3,5-triazines via N -bromosuccinimide (NBS) mediated oxidative C-N bond formation. Isomerisation of [1,2,4]triazolo[4,3- a ][1,3,5]triazines to [1,2,4]triazolo[1,5- a ][1,3,5]triazines is driven by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) affording both isomers with good to excellent yields (70-96%).