3- Methoxy-4- cinnoline 1 -oxide

When the heterocyclic ring contains more than one nitrogen atom, the initial reduction of the A-oxide may take place in the nucleus or the reduction of the nucleus and the A-oxide function occur simultaneously the reduction of quinazoline-3-oxide [317], 3-methoxy-2,5-dimethylpyrazine-l-oxide [414], and cinnoline mono- and dioxide [426] is reported to take this route. 

Recently it has been shown that benzo[c]cinnoline 5-oxide, together with its 3-methoxy and 3,8-dimethoxy derivatives, reacts with dimethyl acetylene-dicarboxylate under forcing conditions to give low yields of the ylides 65-67, formed by electrocyclic ring opening of the initial 1,3-dipolar cycloadducts. This parallels the process that takes place readily with benzo[c]cinnoline A -imides (Section IV,F). 

Note The NMR spectra of cinnoline 1- and 2-oxides have been measured for comparison with those of related diazine oxides. 3-Methoxy-4-(o-nitroanilino)cmnoline 1-oxide (106) underwent deoxygenation to give 3-methoxy-4-(o-nitroanilino)cinnoline (107) (PCI3, CHCI3, reflux. 

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