Synthesis and properties of furan derivatives. 4. Synthesis of 2,5-disubstituted 1,3,4-oxadiazoles containing furan fragments

Synthesis of 2,5-disubstituted 1,3,4-oxadiazoles containing a sterically hindered 4-hydroxy-3,5-di(tert-butyl)phenyl group

“…The above-indicated structure of these compounds is consistent with the data of ultimate analysis and the IR and ESR spectra. Thus, the IR spectra show intense absorption maxima in the intervals 1615-1590 cm -1 and 1495-1460 cm -1, characteristic of the stretching vibrations of the oxadiazole ring [8,12]. The presence of the latter is also confLrmed by the absorption bands at 1250-1225…”

“…The reactions were carried out by boiling the reactants (molar ratio IIc:IV of 1:1.25) in methanol for several hours; the corresponding products IIIe, g, p, q are formed in 67% to 84% yields (see Table 1). In addition, to prepare compounds IIIa, b, we used cyclodehydration of the corresponding N-acyl-N-[4-hydroxy-3,5-di(tert-butyl)benToyl]hydrazines (Va, b) under action of phosphorus oxychloride (method C) [8,10]. Acylation of hydrazides IIa, b with 4-hydroxy-3,5-di(tert-butyl)benzoyl chloride in pyridine formed the corresponding N,N'-diacylhydrazines Va, b (yields, 63-67 %).…”

“…Ia-e Ha-f It is well known [8,9] that convenient compounds used in the synthesis of 1,3,4-oxadiazoles are hydrochlorides of iminoesters of carboxylic acids. In the present study, the starting compounds used were hydrochlorides of ethyl iminoesters of 4-hydroxy-3,5-di(tert-butyl)benzoic (Ia), fl-HDBP-propionic (Ib), s-HDBP-thiocyanic (It), HDBP-thioacetic (Id), and fl-HDBP-propionic (Ie) acids.…”

Synthesis and Antioxidant Activity of 2-Amino-5-R-1,3,4-Oxadiazoles with Hindered Phenol Fragments

“…The 1 H NMR spectra of the obtained compounds show peaks in the region of 9.5-10 ppm, corresponding to the protons of the NH-NH fragment. In accordance with the convenient method [27], the reaction was carried out in an alcoholic alkali solution with the presence of iodine at 0 °C. N-substituted 2-amino-1,3,4-oxadiazoles were obtained in 48-58% yield, with a strong resinification of the reaction mixture, which made it difficult to isolate the products.…”