Available 2‐acylamino‐3,3‐dichloroacrylonitriles, when treated with hydrazine hydrate, provide 2‐alkyl‐ or 2‐aryl‐5‐hydrazino‐1,3‐oxazole‐4‐carbonitriles that readily add alkyl or aryl isothiocyanates and the adducts formed recyclize on heating. Finally, the synthesis results in 5‐alkyl(aryl)amino‐1,3,4‐thiadiazol‐2‐yl(acylamino)acetonitriles or the products of their further cyclization, 2‐(5‐amino‐1,3‐ oxazol‐2‐yl)‐1,3,4‐thiadiazole derivatives. The structures of the novel substituted 1,3,4‐thiadiazoles are corroborated spectroscopically as well as by X‐ray diffraction method. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:454–458, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20041

Available (2-aryl-5-mesyl-1,3-oxazol-5-yl)triphenylphosphonium salts readily react with sodium thiophenolates and their heterocyclic analogs by way of substitution of the mesyl group by an arylsulfanyl or a heterylsulfanyl group. Treatment of the products with sodium hydroxide results in their mild dephosphorylation, which was used for preparative synthesis of a series of 2-aryl-5-arylsulfanyl(heterylsulfanyl)-1,3-oxazoles.Previously we found that substituted vinylphosphonium salts of the general formula Cl 2 C=C . (NHCOR) + PPh 3 An ! regioselectively react with sodium sulfide to form stable mesomeric ylide betaines I and used the latter to success for preparing a series of 5-alkylsulfanyl-2-R-1,3-oxazoles [133]. In the present work, as seen from the scheme below, we studied the conversions of ylide betaines I, leading not only to S-methylation products II, but also to substituted oxazoles III3VII. The most important of the products were found to be new available reagents III containing adjacent mesyl and triphenylphosphonium groups in the oxazole ring. They readily and selectively reacted with sodium thiophenolates or their heterocyclic analogs, and this reaction proved to be a key step in the synthetic sequence III 6 V 6 VI 6 VII. As a result, we could introduce into the 5 position of the oxazole ring four types of sulfur-containing groups: ArS, HtS, ArSO 2 , and HtSO 2 . Furthermore, the 4-Ph 3 P + group could be replaced by hydrogen. The application scope of this convenient synthetic approach to 5-mercapto-1,3-oxazole derivatives is not restricted by the examples in the scheme below, since each of the steps of the sequence I 6 II 6 III 6 V is obviously rather general in nature. Moreover, this approach, even though it involves many steps, offers advantages over other known syntheses of a few representatives of phosphonium salts V, such as condensation of reagent IV and its analogs with thiols [3,4] or reaction of ylide betaines I with arenediazonium salts [3]. The latter method has a fairly narrow field of uses and, in addition, is insufficiently selective. The condensation IV 6 V occurs much more selectively, but the chlorination of ylide betaines I is complicated [3,4] and fails to provide isolable (2-aryl-5-chloro-1,3-oxazol-4-yl)triphenylphosphonium chlorides. Therefore, in the synthesis of phosphonium salts V, we considered it expedient to replace them by the available and analytically pure reagents III.In summary it can be said that the assignment of compounds I3VIII to 1,3-dioxazole derivatives casts no doubts, since the structure of one of the first members of the series of ylide betaines I with R = H, as well as its reaction product with methyl iodide was rigorously proved by X-ray diffraction analysis [5]. Moreover, successive treatment of ylide betaine Ia with hydrogen peroxide and sodium hydroxide gave 2-phenyl-1,3-dioxazole which was also synthesized by independent methods [2]. In addition, the modification of the 5-substituent was followed, as seen from Table 1, by 1 H NMR spectroscopy which gav...

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The comparative analysis of the stimulating effect of low molecular weight heterocyclic compounds, derivatives of pyrimidine, pyrazole, isoflavones, pyridine, oxazolopyrimidine, oxazole and plant hormones auxins IAA (1H-Indol-3-ylacetic acid) and NAA (1-Naphthylacetic acid) on germination of seeds and growth of seedlings of flax (Linum usitatissimum L.) cultivars Ukrainian 3 and Svitanok was conducted. The specific auxin-like stimulating effect of chemical heterocyclic compounds on the basic processes of flax seedlings growth: cell division, cell proliferation, cell elongation and cell differentiation was found. The growth parameters of flax seedlings grown on water solution of chemical heterocyclic compounds used at the concentrations 10-8 M and 10-9 M were similar or higher of the growth parameters of flax seedlings grown on distilled water (control) or on water solution of auxins IAA and NAA used at the same concentrations 10-8 M and 10-9 M. The obtained results proved the possibility of practical application o f derivatives of pyrimidine, pyrazole, isoflavones, pyridine, oxazolopyrimidine and oxazole for intensification of vegetative growth of flax.