Diazomethane 3- pyridazinones

The pyridazinone (474) undergoes cycloaddition reactions with diazomethane to yield the isomers (475) and (476) (Equation (64)). On the other hand, the derivatives (477) give a mixture of (478) and (479) (Equation (65)) <82H(18)175>. Similar results have been reported for the 3-substituted-6-thioxo derivatives <91JHC417>. 

Methylation of 3(2//)-pyridazinones afforded mainly a mixture of N-and 0-methyl derivatives. This is the case with diazomethane (79M12), but... 

Several diazoalkanes have been shown to add as 1,3-dipoles to cyclopropenones. Diazomethane, diazoethane and diazopropane all add in this way to diphenylcyclopropenone to give the corresponding 3,5-diphenyl-4-pyridazinones (equation 66). An exception is 2-diazopropane which yields the diazoketone 73 ... 

Diazomethane and dimethyl sulfate have been used for the methylation of pyrido[3,4-c ]-pyridazinones.136 Diazomethane in dimethylformamide or in benzene reacts with pyrido[3,4-c ]-pyridazine-1,4(2/7,3//)-dione to give l,4-dimethoxypyrido[3,4-c ]pyridazinc (9 ca. 10-20%) together with l-methoxy-3-methylpyrido[3,4-c ]pyridazin-4(3//)-one (10 ca. 40-45%) and 4-mcthoxy-2-methylpyrido[3,4-c/]pyridazin-l(2//)-one (11 ca. 40 -45%), whereas with dimethyl sulfate in aqueous sodium hydroxide, only 1 1 mixtures of 10 and 11 are obtained.136... 

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