Rapid acid hydrolysis of 5-aryl-3-(β-thiomorpholinoethyl)-1,2,4-oxadiazoles

Abstract

was demonstrated by spectral methods and X-ray diffraction structural analysis.Keywords: 5-aryl-3-(-thiomorpholinoethyl)-1,2,4-oxadiazoles, 2-amino-8-thia-1-aza-5-azoniaspiro-[4.5]dec-1-ene chloride hydrate, substituted benzoic acids, acid hydrolysis, X-ray diffraction structural analysis.The possibility that -amino-O-aroylpropioamidoximes and 3-(-aminoethyl)-5-aryl-1,2,4-oxadiazoles exist both as stable bases and hydrochlorides has been demonstrated in our previous work, in which -piperidine, -morpholine, and -benzimidazole derivatives are described. These compounds do not undergo structural change upon isolation from the reaction mixture and recrystallization. Physicochemical and spectral data as well as X-ray diffraction structural data were obtained for these compounds [1][2][3]. Scheme 1 N NH 2 N OH N S O C 6 H 4 X NH 2 N O N O N C 6 H 4 X N XC 6 H 4 COCl N NH 2 N OH S S S -H 2 O 3 2a-e 1a-e 3·2HCl 2HCl HCl · 1,2 a X = p-MeO, b X = p-Me, c X = H, d X = p-Br, e X = m-Cl

Boulton-Katritzky Rearrangement of 5-Substituted Phenyl-3-[2-(morpholin-1-yl)ethyl]-1,2,4-oxadiazoles as a Synthetic Path to Spiropyrazoline Benzoates and Chloride with Antitubercular Properties

“…Nevertheless, for cations in 5c – e and 6 with similar conformations, the mean atomic deviation doesn′t exceed 0.5Å ( Figure 2 b). The positive charge on quaternary ammonium atom causes elongation of N(1)-N(2) and N(1)-C(1) bonds as it was previously demonstrated for 5-aryl-3-[2-(piperidin-1-yl)ethyl]-1,2,4-oxadiazoles [ 9 ], 2-amino-8-thia-1-aza-5-azoniaspiro[4.5]dec-1-ene [ 7 ], 1-( tert -butyl)-4,5-dihydro-1 H -pyrazol-1-ium [ 19 ] and 1,1,3-trimethyl-Δ 2 -pyrazolinium [ 20 ] analogs.…”

“…In some works, we found spiropyrazolinium compounds with a quaternary nitrogen atom, which is common for two heterocycles. When studying the stability of 3-(2-aminoethyl)-5-aryl-1,2,4-oxadiazoles having six-membered cyclic tertiary 2-amino groups towards hydrolysis, we found that they were capable of rearranging to spiropyrazoline benzoates or chlorides [ 7 , 8 , 9 ].…”

“…Particularly, upon keeping 3-[2-(4-phenylpiperazin-1-yl)ethyl]-5-phenyl-1,2,4-oxadiazole recrystallized in 2-PrOH under conditions of air moisture access for nine months for growing single crystals for X-ray structural analysis or by exposure of 3-[2-thiomorpholin-1-yl)ethyl]-5-aryl-1,2,4-oxadiazoles in ethanol with ethereal HCl solution the above-mentioned 1,2,4-oxadiazoles underwent the rearrangement to spiropyrazolinium benzoates or chlorides ( Scheme 2 ) [ 7 , 8 ]:…”

“…Particularly, upon keeping 3-[2-(4-phenylpiperazin-1-yl)ethyl]-5-phenyl-1,2,4-oxadiazole recrystallized in 2-PrOH under conditions of air moisture access for nine months for growing single crystals for X-ray structural analysis or by exposure of 3-[2-thiomorpholin-1yl)ethyl]-5-aryl-1,2,4-oxadiazoles in ethanol with ethereal HCl solution the above-mentioned 1,2,4-oxadiazoles underwent the rearrangement to spiropyrazolinium benzoates or chlorides (Scheme 2) [7,8]: Furthermore, at targeted exposure on 3-[2-(piperidin-1-yl)ethyl]-5-aryl-1,2,4-oxadiazoles with: (i) water, (ii) water in DMF or (iii) ethereal HCl they underwent rearrangement with the formation 2-amino-1,5-diazaspiro [4.5]dec-1-en-5-ium benzoates or chlorides (Scheme 2). In the latter case, along with the formation of spiropyrazolinium chloride hydrate from 3-[2-(piperidin-1-yl)ethyl]-5-(3-chloro-phenyl)-1,2,4-oxadiazole hydrochlorides of starting 1,2,4-oxadiazoles were obtained as secondary products [9].…”

ARYLSULPHONATES OF SPIROPYRAZOLINES AND O-Tosilate-Β-(Benzimidazol-1-Yl)propioamidoxyme AS THE PRODUCTS OF Β-Aminopropioamidoximes TOSYLATION

“…Among the derivatives of β-aminopropioamidoximes, we have accumulated experience of spiropyrazolinium compounds formation [20][21][22]. Boulton-Katritsky rearrangement is a transition pathway of 3-(β-heteroamino)ethyl-5-aryl-1,2,4-oxadiazoles to 2-amino-8-oxa-1,5-diazaspiro [4.5]dec-1-ene-5-ammonium spiropyrazoline benzoates and chloride.…”