Synthese von Heterocyclen, L '). -Synthese von 2,4-Diaryl-5-cyan-l,6-dihydrod-thioxo- 3-pyridincarbonsaure-ethylestern aus u-Benzoylzimtsaure-ethylesternDie Umsetzung von a-Benzoylzimtsaure-ethylestern 2 mit Cyanthioacetamid (1) in Methanol/Natriummethanolat fiihrt zu den Natriumsalzen der 2,4-Diaryl-5-cyan-l,2,3,4-tetrahydro-2-hydroxy-6-mercapto-3-pyridincarbonsaure-ethylester 3. Diese konnen zu MethylthioDerivaten 4 methyliert oder zu Dihydropyridonen 5 dehydratisiert werden. Die Verbindungen 4 werden mittels Nitrosylschwefelsaure zu den entsprechenden aromatischen 2-(Methy1thio)pyridinen oxidiert. Andererseits fuhrt eine ahnliche Behandlung der Derivate 5 zwar zu Aromatisierung, aber isoliert werden die Disulfide 6. Reduktion dieser Disulfide ergibt 2-Thiopyridone 7, woraus die zugehorigen 2-Pyridone 9 hergestellt werden konnen. Diese Produkte entstehen auch bei der basischen Hydrolyse von (Methy1thio)pyridinen 8.In a previous paper in this journal*', we reported on the synthesis of 2-pyridinethiones involving the reaction of cyanothioacetamide (1) with u-benzoylcinnamonitriles from which 4,6-diaryl-1,2-dihydro-2-thioxo-3,S-pyridinedicarbonitriles were obtained. As an extension of this synthesis, we now report on the reaction of 1 with ethyl ct-benzoylcinnamates. This reaction leads to several hitherto unknown 2-pyridinethiones and related compounds.On treatment of ethyl a-benzoylcinnamates 2 with cyanothioacetamide (1) in ethanol solution and in the presence of sodium methoxide as the basic catalyst, conjugate addition at the double bond of the cinnamates 2 takes place, followed by spontaneous cyclization to give a nitrogen-containing ring. However, neither dehydration nor aromatization takes place and the stable sodium salts 3 are obtained. These species seem to be stabilized by an intramolecular hydrogen bond in the configuration shown, responsible for the remarkable high-field shifts of the 'H signals due to the methyl (6 = 0.4) and methylene group (6 = 3.5) (Table 2) of the equatorial ethoxycarbonyl function, shielded by the two contiguous aryl groups. The 'H NMR spectra of these compounds show also a pair of doublets at about 6 = 4.1 and 2.7 with a coupling constant of 12 Hz, indicating a trans-diaxial configuration of 4-H and 5-H. The hydroxy signal appears as a broad singlet at rather low field (6 N 5.8).The OH and NH groups give rise to a broad band at 2800-3600 cm-' in the IR spectra, Liebigs Ann.

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2-Pyridinethiones 3 are obtained in good yields from 1,2,3-triarylpropenones 2 by treatment with cyanothioacetamide 1. Disulfides 4 result from oxydation of 3. Pyridinethiones 3 undergo methylation at the sulfur atom, leading to (methy1thio)pyridines 5, which can be hydrolized to carboxamides 6. Thien0[2,34]pyridines 7 are obtained from 3 upon reaction with methyl chloroacetate.

ChemInform Abstract The propenones (I), on treatment with the thioacetamide (II), undergo Michael addition followed by spontaneous cyclization and aromatization to give the title compounds (III). The latter are used as starting materials for the synthesis of the compounds (IV), (VI), (VII) and (IX).