The results of our study of the pathways of selective reactivity of 3-amino-4-(5-chloromethyl-1,2,4-oxadiazole-3-yl)furazan versus 5-unsubstituted or 5-methyl and 5-trifluoromethyl substituted 4-(5R-1,2,4-oxadiazole-3-yl)furazans (R = H, Me, CF3) towards the action of hydrazine are discussed. If the reductive opening of 1,2,4-oxadiazole ring in unsubstituted at the С-5 atom (1,2,4-oxadiazol-3-yl)furazan derivatives under the treatment with hydrazine can be used as a method for the preparation of a range of amidrazones of 4-R-furazan-3-carboxylic acid. 3-amino-4-(5-trifluoromethyl-1,2,4-oxadiazol-3-yl)furazan with hydrazine gives amidoxime of 4-aminofurazan-3-carboxylic acid. 3-amino-4-(5-methyl-1,2,4-oxadiazol-3-yl) furazan is inert to the action of hydrazine, on the contrary the reaction of 3-amino-4-(5-chloromethyl-1,2,4-oxadiazole-3-yl)furazan with hydrazine leads to oxidation of chloromethyl group of titled compound to the carbonyl one. In this case the product of reaction of 3-amino-4-(5-chloromethyl-1,2,4-oxadiazole-3-yl)furazan with hydrazine was isolated in a form of corresponding hydrazonomethyl derivative notably as 3-amino-4-(5-hydrazonomethyl-1,2,4-oxadiazole-3-yl)furazan. A possible reaction mechanism for the formation of hydrazonomethyl group by oxidation reaction of chloromethyl group by hydrazine is proposed. 3-Amino-4-(5-hydrazonomethyl-1,2,4-oxadiazol-3-yl)furazan undergoes a transhydrazination reaction with semicarbazide and thiosemicarbazide. But our attempts to its hydrolysis for the purpose to obtain free aldehyde were unsuccessful. Thus, hydrolysis of hydrazonomethyl derivative in acetic acid in the presence of catalytic amount of sulfuric acid results in azine – N,N'-bis(3-(4-aminofurazan-3-yl)-1,2,4-oxadiazol-5-ylmethylyden)hydrazine – precipitation, long-duration boiling in hydrochloric acid leads to Kishner-Wolff reduction of the carbonyl group to 3-amino-4-(5-methyl-1,2,4-oxadiazol-3-yl)furazan, and hydrolysis in alkaline medium leads to 1,2,4-oxadiazole ring opening to amidoxime of 4-aminofurazan-3-carboxylic acid. Synthesis of 3-amino-4-(5-chloromethyl-1,2,4-oxadiazole-3-yl)furazan (R = CH2Cl) was carried out by condensation of amidoxime of 4-aminofurazan-3-carboxylic acid with an excess of chloroacetyl chloride in toluene at elevated temperature. The reaction proceeds through formation of intermediate product – 3-chloromethylamino-4-(5-chloromethyl-1,2,4-oxadiazol-3-yl)furazan. Removing of N-chloroacetyl group in such obtained intermediate was performed by hydrolysis in acidic media. One-pot synthesis without the need for isolation and purification of intermediate is allowed. The structures of obtained compounds were proved by modern methods of physical-chemical analysis (1H, 13C NMR, IR and MS spectroscopy).Forcitation:Stepanova E.V., Stepanov A.I. Unusual way of reaction of 3-amino-4-(5-chloromethyl-1,2,4-oxadiazole-3-yl)furazan with hydrazine. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 4. P. 26-32.
Ru(ii)-Peptide bioconjugates with the cppH linker (cppH = 2-(2′-pyridyl)pyrimidine-4-carboxylic acid): synthesis, structural characterization, and different stereochemical features between organic and aqueous solvents
