A. Krauze, G. Duburs
2000
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0
Influential Citations
3
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Journal
Heterocyclic Communications
Abstract
4,5-trans-4-Aryl-3-cyano-6-hydroxy-6-methyl-5-pyridinio-1,4,5,6-tetrahydropyridine-2-thiolates 4 were obtained by cyclocondensation of 1-acetonylpyridinium chloride 1, aromatic aldehyde 2 and cyanothioacetamide 3. 6-Hydroxy-6-methyl-4-phenyl-5-pyridiniohexahydropyridine-2-thione chlorides 5, occurring as a mixture of thione and enethiol tautomers, were prepared by treatment of thiolate 4a with hydrochloric acid. Dehydration and dehydrogenation of thiolates 4 have been carried out as well. Steric structures of hydrogenated 6-hydroxypyridines 4. 5 are discussed in the light of NMR spectra. Introduction 3-Cyano-l,4-dihydropyridine-2(3H)-thiones are of interest both for synthetic organic chemistry (particularly as intermediates in the synthesis of new heterocyclic systems) and for the search of biologically active compounds [1-4]. 5-Acetyl-2-alkylthio-6-hydroxy-4-pyridyl-1,4,5,6-tetrahydropyridines have revealed pronounced cardiovascular activity [5], but unfortunately they were unstable compounds capable of splitting off water (usually completely at pH 2-3 and 40*C). Electronwithdrawing substituents in position 5 and bulky aryl groups in position 6 were found to be suitable for obtaining such compounds [4-10], On the other hand, 3-cyano-l,4-dihydropyridine-2(3H)-thiones bearing a pyridyl group in positions 4 or 5 were found to exist in the form of betaines [4,9-14], So far, betaines of 6-hydroxy-4-(2-, 3or 4pyridyl) or 5-(2-,3or 4-pyridyl)-l,4,5,6-tetrahydropyridine-2-thiones have not been described in literature, obviously, since they are unstable due to dehydration. In continuation of our work on the synthesis of 2-alkylthio-6-hydroxy-1,4,5,6-tetrahydropyridines [10] and on the use of pyridinium ylides [15,16] as building blocks for new heterocyclic systems, we