7-Methyl-3- -pyridinethione

CgH7NS = l-methyl-2(lH)-pyridinethione),1257 [Ag(C7N2S2)2]Br,1258 and [AgBr(mbi)] (mbi = methyl-2-thiobenzimidazole) have been reported.12... 

Application of pulsed ion gas-phase cyclotron resonance (ICR) spectroscopy to proton affinities of the derivatives 2-methoxypyridine and N- methylpyridin-2-one confirm previous deductions on the enthalpy of 2-hydroxypyridine-pyridin-2-one tautomerism (76JA6048), provided that the difference between the influences of O-methylation on 2-hydroxypyridine and A-me thy lat ion in pyridin-2-one are taken into account. These measurements have been further clarified and extended to other gas phase basicity measurements (79JA1361). A similar estimation of the gas phase basicities of 2- and 4-pyridinethiols and 2- and 4-pyridinethiones confirms that the thiol form is predominant in the gas phase (77TL1777), in line with previous studies involving mass spectrometric deuterium isotope studies (75BSB465). Photoelectron spectroscopy has also been employed in such studies (see Section 2.04.3.6 and Figure 21 for details) <77JCS(P2)1652>. 

Reactions of 3-hydroxy-6-methyl-2(lfl)-pyridinethione with 1,3-dibromo-propanes in methanol in the presence of sodium methylate yielded betaines (205) (70ACS2949). 9-Hydroxy-3,4-dihydro-2f/-pyrido[2,l-6][1,3]-thiazinium bromide was obtained in the reaction of 3-hydroxypyridine-2(lH)-thione and l-bromo-3-chloropropane in boiling toluene [81JCR(S)208]. 

Cyclocondensations of benzylidenemalononitrile with pyridinethiones 210 and 211 afforded the amino derivatives of pyrido[2,l-h][l,3]thiazines 212 and 213, respectively (90MI2 92MI6). Reaction of 5-acetyl-3-cyano-6-methyl-4-phenyl-3,4-dihydropyridine-2(lfl)-thione with epichlorohydrin in the presence of potassium hydroxide and sodium methylate gave 7-acetyl-3-hydroxy-6-methyl-8-phenyl-2,3,4,8-tetrahydropyrido[2,l-h][l,3]-thiazine-9-carbonitrile (94KGS139). 

Reaction of tertiary enaminones with benzoyl isothiocyanate gives substituted 2-pyridinethiones in moderate yields, indicating the reactivity of enaminones at a-methyl group6 (equation 2). Phenylisothiocyanate reacts simply at the -position7 (equation 3). 

POCI3 chlorinations (Eq. (8)) are acid-catalyzed reactions of such reaction products]. The hydrogen bonding of azinones is related to that of i r-oxides, discussed below, and to that of ketones (with water and alcohols) and has been demonstrated by infrared measurements on pyridinethione in alcohols and by the electronic absorption spectra of azinones in water. 6-Chloro-l,3-dimethyl-pyrimidine-2,4-dione is rapidly aminated at 20° (with heat evolution) by methyl- or ethyl-amines, etc., in protic media (water or alcohols). 

Tautomeric constants of several 2-substituted 5-methoxy-4(l//)-pyridinethiones were determined by comparing their pKa values with those of their 4-methylthio- and V-methyl analogs, measured spectrophotometrically in water at 25 °C. The KT values are affected by the substituent at the position 2 and are decreased by electron-withdrawing groups. The thione forms predominate in aqueous solution by factors of ca. 105 for 5-methoxy-2-methyl-4(l//)-pyridinethione and ca. 105 for 5-methoxy-2-hydroxymethyl-4(l//)-pyridinethione (77BCJ3295). 

Ricinidine (74) has been synthesized in three steps from 3-formyl-l-methyl-2(lH)-pyridinethione [206],... 

The 1,2-5y -configured radical 45 does not cyclize stereoselectively. Both dia-stereomeric bromomethyl-substituted tetrahydrofurans 3,5-/ra 5-44 and 3,5-cis- 44 are obtained in equal amounts from the photoreaction of pyridinethione 43 and BrCCh (Scheme 11). This observation is explained by the transition state model for intermediate 45, where the methyl and the benzoyloxy substituent should both compete for / . eMconformationally flexible intermediate 45. 

P4S10 to yield pyridinethione 140, which by methylation afforded 141. Dichloro-malononitrile was cyclized to give 2,5-dichloronicotinonitrile. Arylazomalononitrile 142 was reacted with guanidinium salt 143 to yield arylazopyrimidine 144170,171 Perhydropyrimidines and -triazines were prepared from (H2N)2C=N—CN 2-ethyl-2-phenylmalononitrile. Tetracyanoperhydropiperazines were obtained from amino-malononitrile salts and aromatic aldehydes... 

Hydroxy-2-pyridinethione 2-(2 -Hydroxyphenyl)oxazoline N, N, N"-Trimethyl-1,4,7-triazacyclononane 2-(2-Pyridyl)ethylbis(6-methyl-2-pyridylmethyl)amine 2-(2-Pyridyl)ethylbis(2-pyridylmethyl)amine 1,10-Phenanthroline... 

The relative stabilities of these two sulfur analogs should be compared with the tautomeric equilibrium of 2-thiopyridine where the pyridinethione tautomer predominates in aqueous solution. These observations demonstrate that tautomeric equilibria in protic systems cannot be used reliably to predict the relative stabilities of the methylated isomers. It has been shown recently that 0-mesyloxypyridines (MI-506)are more stable than A -mesyl-2-pyridones. ... 

R.I. 1145). 3-Hydroxy 2-pyridinethione (W-542, R = H) and 3-hydroxy-6-methyl-2-pyridinethione (XII-542, R = CH3) and ethylene bromide in methanol containing sodium methoxide react to give dihydrothiazolo[3,2-a]pyridinium 8-oxides (XII-543). Methyl 2,3-dibromopropionate and XII-S42 form... 

Equilibration of A -methyl-2-pyridinethione (XII-74S) with 2-methylthio-pyridine in the presence of y/-methyl-2-methylthiopyridinium tetrafluoroborate showed that the thioether is the more stable in the liquid phase [/iTeq. 14.4 (188 ), 10.7(145°)]. ... 

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