Novel fused azecine ringsystems were synthesized via the microwave-assisted thermal isomerization of terphenyl or biphenyl-pyridazine compounds possessing a vinyl and a tert-amino group, through application of a new extension of the tert-amino effect. Substrates for the ring closure were prepared from ortho-dihalobenzene or pyridazinone by consecutive Suzuki couplings with ortho-sec-amino- and formylphenylboronic