SYNTHESIS AND NITROGEN ELIMINATION OF 3-ARYLTETRAZOLO(1,5-a)PYRIDINIUM SALTS AND ITS ANGULAR BENZENOLOGUES Formation of N-arylamino-α-pyridones, -quinolones, -isoquinolones, and phenanthridones

Article abstract of DOI:10.1016/S0040-4020(01)82063-9

2-Pyridyl aryltriazenes (2) as well as 1-isoquinolyl-, 2-quinolyl- and 6-phenanthridyltriazenes (6, 9, 12) undergo cyclization in the presence of 2,4,4,6-tetrabromocyclohexa-2,5-dien-1-one (3) and result in 3-aryl-tetrazolo(1,5-a)pyridinium salts (4) and its angular benzenologues (7, 10, 13).These new tricyclic (7, 10) and tetracyclic (13) angularly fused tetrazolium salts when treated with tetraalkylammonium hydroxide result in rapid nitrogen elimination under mild conditions and give rise to N-aryl-aminoisoquinolones, -quinolones and -phenanthridones (14, 15, 16).In the case of the bicyclic tetrazolo(1,5-a)pyridinium salts (4) a nitrogen elimination reaction - analogous to that found with the tricyclic tetrazolium salts - can, however, be observed only by using alkoxides as reagents: thus, tetrazolyldieneethers (18) and N-arylaminopyridones (19) are simultaneously formed.