The possibility of preparing 1,2,5-oxa-, -thia-, and -selenadiazole N-oxides from polyfunctional nitroso-and isonitrosopyrimidines and -pyridine was examined.We found previously that the reactions of 6-amino-5-nitrosouracils with sulfur or selenium monochloride yield 1,2,5-chalcogenadiazolo [3,4-d]pyrimidines [1,2]. In this study we examined the applicability of this reaction to o-amino nitroso compounds containing additional reaction centers such as hydroxy and amino groups. As starting compounds we used 5-nitroso derivatives of 1-hydroxyethyl-6-aminouracil (Ia) [3], 4,6-diamino-1,2-dihydropyrimidin-2-one (Ib) [4], and 2,4,6-triaminopyrimidine (Ic) [4], and also 3-nitroso-2,6-diaminopyridine Id [5]. Treatment of Ia3Id with sulfur or selenium monochloride under the conditions similar to those described in [1] resulted in formation of 1,2,5-chalcogenadiazole N-oxides IIa3IIh in good yields (Scheme 1).The reactive functional groups present in the starting amino nitroso compounds, at equimolar ratio of the reactants, exert no appreciable effect on the course of cyclization with the formation of 1,2,5-thiadiazole N-oxides and their selenium analogs.An alternative route to 1,2,5-oxa-, -thia-, and selenadiazoles, based on transformations of aliphatic and aromatic 1,2-dioximes [6 38], is limited by difficult availability of heterocyclic 1,2-dioximes.With 6-amino-5-nitrosouracil Ie as example, we showed that the amino group in an acidic medium is readily replaced by hydroxylamine; the reaction product isomerizes into uracil 5,6-dioxime IIIa existing, according to single crystal X-ray diffraction data, in the form of the (4Z,5E) isomer [9]. The reactions between Ib3Id and excess hydroxylamine taken as a mixture of acetate and hydrochloride resulted in replacement of all the amino groups with the formation of tri-and tetraoxime derivatives of pyrimidine (IIIb, IIIc) and pyridine (IIId) (Scheme 2). The reactivity is apparently influenced by the steric factors: 1-Substituted 6-amino-5-nitrosouracils do not react with hydroxylamine under the similar conditions. Scheme 1.
4-Amino-and 4-ureido-1,2,3-triazole-5-carboxylic acid oxides, as well as their hydrazides and methylamide, were prepred via pyrimidine ring opening in isomeric 2-phenyl[1.2.3]triazolo [4,5-d]pyrimidine-5,7-dione N-oxides. Recyclization of the pyrimidine ring in azolopyrimidines under the action of nucleophiles provides a convenient synthetic approach to heteroaromatic amino acids and their derivatives. This approach has been used to prepare coffeidine [1], previously hardly available 3-amino-and 3-ureido-1,2,5-triazole-5-carboxylic acids and their amides, anilides, and hydrazides [234], as well as amino acids of the oxaand selenadiazole series [5].The aim of the present work was to extend the above approach to derivatives of 1,2,3-triazole ÄÄÄÄÄÄÄÄÄÄÄÄ N-oxides.We found that boiling of 2-phenyl[1.2.3]triazolo-[4,5-d]pyrimidine-5,7-dione 1-oxide (Ia) [6] with aqueous sodium hydroxide and ammonia results in hydrolysis of the pyrimidine ring to form 4-amino-(II) and 4-ureido-2-phenyl-1,2,3-triazole-5-carboxylic acid 1-oxides (III), respectively. Unlike the reaction with aqueous ammonia, the reaction of compound Ia with aqueous methylamine provides N-methyl-2-phenyl-4-ureido-1,2,3-triazole-5-carboxamide 1-oxide (IV). Scheme 1.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.