The infrared spectra of some pyridones and quinolones and their behaviour in the Kolbe–Schmitt reaction

Abstract

The cyclic amido-structure of 2-pyridone, 6-methyl-Z-pyridone, 2-quinoloce, and 4-methyl-2-quinolone in the solid state and in solution has been confirmed by infrared measurements. The spectra of sodium 2-pyridyl oxide and potassium 2-quinolyl oxide have also been examined and a chelated structure for potassium 2-quinolyl oxide is suggested to explain its inertness in the Kolbe-Schmitt reaction.IT is well known that the pyridones and analogous compounds are tautomeric with respect to the keto and the enol forms. For 2-pyridone these are represented by (I) and (11) respectively, probably being stabilised by resonance with the dipolar forms (111) and (IV). ) showed by a study of the ultraviolet absorption spectra that in methanolic solution 2-ar,d 4-pyridone exist substantially in the amido-form. Addition of alkali led to marked spectral changes which were ascribed to a change towards the enol form. The spectrum of 3-hydroxypyridine, however, was not greatly affected by either alkali or acid. Leis and Curran ( J . Amer. Chem. SOC., 1945, 67, 79), on the basis of the dipole moment for a dioxan solution, concluded that in this solvent 4pyridone

The Tautomeric Persistence of Electronically and Sterically Biased 2‐Quinolinones

“…[26][27][28][29][30][31] In solution, as opposed to the gas phase, pyridines and quinolines carrying oxygen at the 2-or 4-position were found to exist as 2-or 4-pyridinones and 2-or 4-quinolinones rather than as 2-or 4-hydroxypyridines and 2-or 4-hydroxyquinolines. This assignment was based on the comparison of their UV [32][33][34][35][36][37] and IR [38][39][40][41] spectra, their dipole moments [42] and their dissociation constants [24,43] with data collected from model compounds where the lactam and lactim functions had been made immutable ("frozen") by Nand O-methylation, respectively. However, according to all available evidence, the relative thermodynamic stabilities of the oxo and hydroxy forms cannot be far apart.…”

Caerulomycin, a new antibiotic from Streptomyces caeruleus Baldacci. II. Structure

“…Furthermore, the dipyridyl derivative VI exhibits an infrared absorption maximum in chloroform solution a t 3 355 cm-l, a wavenumber appreciably lower than the value of 3 595 cm-I reported for 3-hydroxypyridine, and within the range (3 367 -3 442 cm-I) found for 2-and 4-pyridones (10). In the C=C stretching region, the absorption maximum a t 1 641 cm-I is close to the maxima recorded for the carbonyl or ring stretching frequencies of 4-pyridone (1 638 cm-I (10)) and 2-pyridone (1 654 cm-I (lo), 1 619 and 1 656 cm-I ( l l ) , 1 608 and 1 650 cm-I (12)) but much higher than that recorded for 3-hydroxypyridone (1 580 cm-I in CHC13 solution (12), 1 560 -1 572 cm-I in pressed KC1 or KBr (10,12)). Facile replacement of the hydroxyl with chlorine by reaction with phosphorus pentachloride is also more readily explained if the oxygen substituent is alpha or gamma to the ring nitrogen.…”

Infrared spectra of 2-pyridone-16O and 2-pyridone-18O

“…The band numbered 11 has not been reported previously for 2-pyridone-160 in solution although a shoulder in the solid state spectrum at 1680 cm-' has been reported (14).…”