Pyridazino 1,2-6 phthalazine-6,11 -dione

The steric course of electrophilic additions of BrN3, IN3, and iV-bromosuccinimide (NBS) to the tetrahydropyridazine ring of benzo[g]pyridazino[l,2- ]phthalazine-6,13-dione system, for example, 130, has been studied and the results are shown in Scheme 12 <1997CJC348>. 

Pyridazino l,6-6 indazole, 768 lS ridazino[4.3-6 indoie, 1024 l ridazino 6,l-o isoindole, 1055 F ridazino l,2-6 phthalazine-6,l l-dione,... 

The reactivity of pyridazines in Pd-catalyzed reactions was of interest. For example, the Heck alkenylation at C5 of 6-phenyl-3(2//)-pyridazinones was investigated, with the aim of suppressing production of 4-phenyl-6-substituted-2-phthalazinone byproducts <04TL3459>. In another study, the reactivity of 5-iodopyridazin-3(2f/)-ones in Pd-catalyzed reactions was investigated to develop an efficient route to 2,5-disubstituted pyridazin-3(2/f)-ones <04T12177>. Other pyridazine syntheses relied on condensation approaches. Benzo[g]pyridazino[l,2-i>]-phthalazine-6,13-diones 16 and 17 related to certain anthracyclinones were obtained by cycloaddition of 1,3-dienes to benzo[g]phthalazine-l,4-dione <04H(63)1299>, and pyridazine C-nucleosides synthesized by 14-i-2 cyclocondensation of alkynyl C-nucleosides with substituted tetrazines afforded, upon extrusion of a nitrogen atom, pyrrole C-nucleosides in good yields... 

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