Equilibrium studies: Substituent effects on methoxypyridine-1-methylpyridone equilibria

Cycloadditions in syntheses. XXXII Intramolecular photocycloaddition of 4-(.OMEGA.-alkenyloxy)quinolin-2(1H)-one : Synthesis of 2-substituted cyclobuta[c]quinolin-3(4H)-ones.

“…Previously we have demonstrated that, while 1,2-dihydrocyclobuta[c]quinolin-3(4H)-one.cycloadds to olefins to give two regio-isomers in ca. 1: 1 ratio, 1-substituted derivatives afford only the head-to-head adduct [9,10-disubstituted phenanthridin-6(5H)-ones: D] regioselectively, and we pointed out that the presence of the 1-substituent plays an important role in this selectivity.7a, 19) In the present case, it is clearly demonstrated that the presence of the acetoxymethyl group at the 2-position is essential for the formation of 7,8-disubstituted phenanthridone (22). The 7,9-disubstituted product (23), though obtained, was only the minor product (ca.…”

The Tautomeric Persistence of Electronically and Sterically Biased 2‐Quinolinones

“…Org Viewed against this background there was little reason to expect the yet unknown 3-fluoro-2(1H)-pyridinone or regioisomers thereof (e.g., the 6-fluoro analog [75] ) not to favor the lactam form. As the driving force for switching into the aromatic hydroxyimine structures is in the quinoline series even smaller than in the pyridine series, [17,[76][77][78] we did not really believe 3-fluoro-2(1H)-quinolinones, assisted or not by a bulky 8-substituent, to populate the lactim tautomer to a significant extent. This sceptical expectation having been confirmed by the present investigation, we are happy to follow Katritzky's advice to "call a spade a spade" [79] and to call a 3-fluoro-substituted 2(1H)-quinolinone also in the future a quinolinone.…”

Reactions of Hydroxypyridines with 1-Chloro-2,4,6-trinitrobenzene − Product Structure, Kinetics, and Tautomerism

“…It is a reaction different to a simple shift from O to N, such as in the case of alkyl group migration derivatives of 2-alkoxypyridines under acid catalysis or on heating in solution. [33] Probably, for moieties sterically less hindered than the trinitrophenyl group, a pathway similar to that in Scheme 6 may explain the apparent migration from O to N of alkyl or aryl groups of derivatives of hydroxypyridines. The structure of 15 was ascertained by single-crystal X-ray analysis ( Figure 1).…”