Quinolinium-8-olates

The methyl and benzyl derivatives (289 R = Me, PhCH2 R = H) were described by Claus and Howitz in 1891. Their preparation involves N-alkylation of 6-hydroxyquinoline and base hydrolysis to the quaternary hydroxide which is then desiccated, giving the hygroscopic betaines 289. ° The 2-phenyl derivative (289 R = Me, R = Ph) has been similarly prepared. With methyl iodide, the phenol betaine (289 R = Me, R = H) gives Af-methyl-6-methoxyquinolinium iodide.  

Diazoxine, a red product which accompanies the formation of 8-methoxy-quinoline from 8-hydroxyquinoline and diazomethane, was first encountered by Caronna and Sansone in 1939. Later, it was suggested that the properties of this product were consistent with structure 189 (R = Me, R = R = H). ° Subsequently, this product has been prepared by treatment of the iodide 190 with potassium carbonate, and the betaine structure has been confirmed by spectroscopic and chemical studies. Compound 189 (R = Me, r2 = r3 = H) is isolated as hydrated violet-red needles. The UV and visible spectra are strongly dependent on the nature of the solvent the colors of solutions vary from yellow to blue. 1 Bromination gives the 5,7-dibromo 

7-dibromo-8-hydroxyquinoline and diazomethane. Treatment with hydrochloric acid gives a hydrochloride. 

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The study of reactions between mesomeric betaines and 1,3-dienes has so far been restricted to pyridinium-3-olates (Section III,A,2) and quinolinium-3-olates (Section III,B, 18). The mode of addition of dienes differs from that of 23T-electron addends in two respects (i) Dienes add across a different... 

Fig. 9. Frontier orbital mixing for the thermal addition of 1,3-butadiene to V-methyl-quinolinium-3-olate (467 -> 468).

Dennis, Ibrahim, and Katritzky demonstrated the addition of 1,3-dienes to mesomeric betaines. They prepared adducts from A-pyridyl and A-pyrimidinylpyridinium-3-olates and various dienes (including cyclopentadiene) and have analyzed the frontier orbital interactions in some detail.Almost simultaneously, Mok and Nye discovered that V-methyl-quinolinium-3-olate (467), generated in situ, gives adducts (e.g., 468) with several 1,3-dienes, and using the HMO method they showed that the frontier orbital interactions during addition (Fig. 9) are favorable for transition state stabilization. ... 

The oxoaporphine alkaloids Teliglazine (126), Corunnine (127), Nandazurine (128), PO-3 (129), A-Methylliriodendronine (130), and A,(9-Dimethylliriodendronine (131) contain the 6-methyl-7-oxo-dibenzo [Je,g]quinolinium-l-olate ring system 125 which is isoconjugate with the l-methyl-7-methylene-7H-benzo[Je]anthracene anion (Scheme 46). Therefore, these alkaloids belong to class 1, i.e., heterocyclic mesomeric betaines isoconjugate with odd alternant hydrocarbon anions. Another... 

On the other hand, 3-hydroxyquinoline-2(l//)-thiones 645 (readily available from the corresponding isatins) were converted into 1,2-dihydrothiazolo[3,2-fl]quinolinium-4-olate 646. Ring opening of 646 gave the N- and S-vinyl derivatives 647 and 648, respectively (84ACSA(B)109) (Scheme 112). 

As in the preceding subsection, l,2-bis(benzenesulfonylimino)-4,5-dimethyl-benzene (598) and 2-phenylthiazolo[3,2-fl]quinolinium-l-olate (599) in dichloromethane at 20°C during 15 min afforded l,4-bis(benzenesulfonyl)-6,7-dimethyl-3-phenyl-3-(quinolin-2-ylthio)-3,4-dihydro-2(l//)-quinoxalinone (600) in almost quantitative yield. " ... 

The study of reactions between mesomeric betaines and 1,3-dienes has so far been restricted to pyridinium-3-olates (Section III,A,2) and quinolinium-... 

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