Approaches to 1,1-disubstituted cinnolin-3-ylio oxides: synthesis and reactivity of a new class of heterocyclic betaines

The cinnolin-3-ylio oxides 6, a new class of heterocyclic aminimide, can be prepared by intramolecular cyclization of the N',N'-disubstituted (2-fluorophenyl)acetohydrazides 5. Attempts to prepare these betaines by an alternative route, namely cyclization of the nitrenes expected from the thermal decomposition of (2-dialkylaminophenyl)acetyl azides 11, failed, Curtius rearrangement-derived compounds being the main products isolated from these processes, Hydrochlorides of the cinnolin-3-ylio oxides 6 undergo alkyl halide elimination to yield the 1-(omega-chloroalkyl)cinnolin-3-ols 19a,b or 1-methylcinnolin-3-ol 21. Oxidation of the latter to the 3-hydroxycinnolin-4-one 22, its methylation to the corresponding N-1,O- 23 and N-1,N-2-dimethyl 24 derivatives as well as the cyclization of 1-(5-chloropentyl)cinnolin-3-ol 19a to the diazepino[1,2-a]cinnolinone 20 are also reported.