Pyridazino pyridazines

Structural problems in the pyrido[3,4-c]pyridazine series (76CPB1870) and in the fused pyridazino[4,5-6]quinoline series (80CPB3457) have also invoked mass spectral determinations. 

True electrophilic substitution is very difficult in pyridopyridazines. For example, the [3,4-d] parent (286) is inert to hot 65% oleum (68AJC1291), and although formation of a 3-bromo derivative (308) was reported in the [2,3-d] series, it seems to have arisen by an addition-elimination reaction via the dibromide (309) (69AJC1745). Attempted chlorination led to ring opening. A similar effect was observed in the [3,4-d] system, where an 8-bromo derivative was obtained (77BSF665), and in iV-oxides of the pyrido[2,3-c]pyridazine and fused pyridazino[3,4-c]isoquinoline series (72JHC351). The formation of (311) from (310)... 

Pyridazine 1-oxide N NMR, 2, 17 <80HCA504) Pyridazino[4,5-d]azonine-7-carboxylic acid, 1,4-dipbenyl-, etbyl ester... 

Pyridazinium salts, 1-methoxy-reaction with pyridazines, 3, 23 Pyridazino[4,5-6]azepines synthesis, 7, 522 Pyridazino[4,5-d]azepines synthesis, 7, 522 Pyridazinofuroxans synthesis, 6, 425 Pyridazinoheteronins synthesis, 7, 729 Pyridazino[2,3-a]indole synthesis, 4, 297... 

Pyridazino[4,5 -c]isoquinoIine, 6-aryI-synthesis, 3, 244 Pyridazino[3,4-c]isoquinoIines alkylation, 3, 238 JV-oxide, 3, 327 synthesis, 3, 247-248 Pyridazino[4,3-c]isoquinolines synthesis, 3, 247 Pyridazino[4,5-c]isoquinolines alkylation, 3, 238 Pyridazin-3(2H)-one, 6-acryIoxy-polymers, 1, 288... 

Pyridazino[4,3-c]pyridazine, 2,6-dimethyl-3,4-dioxo-2,3,4,6,7,8-hexahydro-4-( p-bromophenylhydrazone) synthesis, 3, 352... 

Pyridazino[4,5-d]pyridazine, hydroxy-IR spectra, 3, 333 methylation, 3, 343 tautomerism, 3, 333... 

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