Ring closure of ortho-blocked 4-aryl-1,2,4-triaza-1,3-dienes via 1,6-electrocyclisation followed by Diels–Alder dimerisation

Abstract

1-Acyl-4-(2,6-dimethylphenyl)-1,2,4-triaza-1,3-dienes (7), generated in situ upon manganese dioxide oxidation of the corresponding N-acyl-N′-(2,6-dimethylphenylaminomethylene)hydrazines (6), give the bridged heterocyclic compounds (10)via 1,6-electrocyclisation followed by Diels–Alder dimerisation. The isonitrile (8) is also obtained as a minor fragmentation product.