Studies toward the synthesis of 4-(2-R-ethyl)amino-2,2,5,5-tetramethyl-3-imidazoline 1-oxyls. Nucleophilic substitution of bromide in the N-alkyl chain of the 1,2,4-oxadiazol-2-one precursor Full article
| Journal |
Journal of Organic Chemistry
ISSN: 0022-3263 |
||||||
|---|---|---|---|---|---|---|---|
| Output data | Year: 2008, Volume: 73, Number: 2, Pages: 502-510 Pages count : 9 DOI: 10.1021/jo701803a | ||||||
| Authors |
|
||||||
| Affiliations |
|
Abstract:
[GRAPHICS] A synthetic approach to access the new nitroxides of the amidine type exhibiting pH-dependent EPR spectra through substitution of a halide in the exo-N-halogenoalkyl chain of 1-(2-bromoethyl)-6-oxyl-5,5,7,7-tetramethyltetrahydroimidazo[1,5-b][1,2,4]oxadiazol-2-one is reported. In this approach, an oxycarbonyl moiety of the oxadiazolone heterocycle plays the role of a "protecting group" for the amidine functionality. A nucleophilic cleavage of the oxadiazolone heterocycle under mild nonbasic conditions, applicable to substrates bearing substituents vulnerable to attack by strong basic nucleophiles, is elaborated. The approach allows for the new amidine nitroxides bearing various functional groups (e.g., such as CN, N-3, NH2, COOEt) to be synthesized. A series of nitroxides obtained through the Staudinger/intermolecular aza-Wittig reaction of the azido derivative is also described. The nitroxides synthesized here were found to have pfl-dependent two-component EPR spectra indicative of a slow, on the EPR time scale, R-center dot reversible arrow (RH+)-H-center dot chemical exchange, and pK(a) values ranging from 2.8 to 12.5 units. The guanidine derivatives synthesized in this work show the highest pK(a) values (pK(a) = 10.2 and 12.5, respectively) ever reported for the nitroxide pH-probes of a "basic type".
Cite:
Polienko J.F.
, Schanding T.
, Gatilov Y.V.
, Grigor'ev I.A.
, Voinov M.A.
Studies toward the synthesis of 4-(2-R-ethyl)amino-2,2,5,5-tetramethyl-3-imidazoline 1-oxyls. Nucleophilic substitution of bromide in the N-alkyl chain of the 1,2,4-oxadiazol-2-one precursor
Journal of Organic Chemistry. 2008. V.73. N2. P.502-510. DOI: 10.1021/jo701803a WOS Scopus РИНЦ OpenAlex
Studies toward the synthesis of 4-(2-R-ethyl)amino-2,2,5,5-tetramethyl-3-imidazoline 1-oxyls. Nucleophilic substitution of bromide in the N-alkyl chain of the 1,2,4-oxadiazol-2-one precursor
Journal of Organic Chemistry. 2008. V.73. N2. P.502-510. DOI: 10.1021/jo701803a WOS Scopus РИНЦ OpenAlex
Dates:
| Published online: | Dec 18, 2007 |
| Published print: | Jan 1, 2008 |
Identifiers:
| Web of science: | WOS:000252325200020 |
| Scopus: | 2-s2.0-40949131732 |
| Elibrary: | 13594280 |
| OpenAlex: | W2087316309 |