Cinnolinium-8-olates

The net charges and HOMO coefficients on the O and N(6) of pyrido[2,l-a]phthazinium-7-olate (20) and pyrido[l,2-h]cinnolinium-ll-olate (21) were calculated with the AMI method (92CB929). 

Methylation of pyrido[l,2-6]cinnolinium-ll-olate (17, R = H) with the soft dimethyl sulfate gave only the A -methyl derivative 43 (74JHC125), whereas the harder trimethyloxonium tetrafluoroborate yielded the 11-methoxy derivative 77 (92CB929). Methylation of pyrido[2,l-a]phthal-azinium-7-olate (20) with methyl iodide afforded a 1 9 mixture of the... 

The chemical reactions of the cinnolinium-4-olates (233) are conveniently illustrated by considering specific reactions of the 2-methyl derivative (243) (Scheme 10). Compound 243 readily forms salts Ethanolic hydrogen chloride gives 2-methyl-4-hydroxycinnolinium chloride (239) and tri-ethyloxonium tetrafluoroborate gives 2-methyl-4-ethoxycinnolinium tetra-... 

Several 1,3-dipolar cycloaddition reactions of cinnolinium-4-olates have been reported. The methyl derivative (243) with dimethyl acetylenedicarboxylate gives adduct 247. Previously, the formation of a 1 1 adduct between compound 243 and phenylacetylene had been reported by Lunt and Threlfall. The 6-chloro derivative (233 R = Me, R = R = R = R = H, R = Cl) forms similar adducts with dimethyl acetylenedicarboxylate and diphenylacetylene and a single regioisomer with phenylacetylene. No reaction with olefinic dipolarophiles was observed. 

Two representatives of this system (248 R = H, OMe) have been prepared by reaction of the corresponding cinnolinium-4-olates (249 R = H, OMe) with phosphorus pentasulfide. Menschutkin methylation gives the cinnolinium iodide 250 (R = H). ... 

Compounds of this type are readily prepared from the pyrido[l,2-6]-cinnolinium-ll-olates (338) (Section III,D,1) by reaction with phosphorus pentasulhde. Alkylation with ethyl bromoacetate gives the 11-ethoxycar-boxylmethylthio salts (349) which are useful intermediates for preparing other derivatives (Sections III,D,2 and 3). Hydrolysis of 349 regenerates the betaines 348. 

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