Synthesis of Substituted 2-Amino-6H-1,3-oxazin-6-ones

Derivatives of the unknown 2-amino-6H-1,3-oxazin-6-one 2 have been synthesized for the first time in two steps and in excellent yields, starting from N-cyanocarbonimidates 3a – c and cyanoacetates. The structures of 2a – c are assigned by NMR-spectroscopic methods and corroborated by an X-ray structure analysis of 2c .     

Mass-spectrometric study of 5,6-dihydro-4H-1,3-oxazin-5-ones

Under the influence of electron impact, 2-aryl-1,3-oxazin-5-ones undergo fragmentation primarily with the elimination of the C₂H₂O₂ group of atoms, as well as with the formation of aroyl cations. The complete absence of the retrodiene fragmentation that is characteristic for such heterocyclic systems makes it possible to conclude that the double bond in the heteroring is not stabilized. In the case of 4-alkyl- and 4-benzyl-substituted oxazinones the molecular ions under-go rearrangement, as a result of which a seven-membered heteroring is formed due to inclusion of the methylene group of the substituent in an oxazine ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 43–47, January, 1981.     

Potentiometric study on acid properties of some 4-hydroxy-6H-1,3-oxazin-6-ones. Structure-biological activity relationship

4-Hydroxy-6H-1,3oxazin-6-ones exhibit properties of weak OH acids. These compounds are readily methylated with diazomethane to give the corresponding 4-methoxy derivatives. According to the potentiometric titration data, the pK _a values of 2-methoxy-and 2-methylsulfanyl-substituted 4-hydroxy-6H-1,3-oxazin-6-ones range from 7.45 to 8.42, depending on the substituent in position 5 of the heteroring. 4-Hydroxy-6H-1,3-oxazin-6-ones in biological media exist mainly in the neutral form.     

Facile and convenient synthesis of 2,6-disubstituted 4H-1,3-oxazin-4-one derivatives

Facile and convenient methods for the preparation of a variety of 2,6-disubstituted 4H-1,3-oxazin-4-ones 3 by three complementary methods are described. Treatment of the branched aliphatic imidate 2c,d with diketene 1 in the presence of a catalytic amount of acetic acid affords 2-substituted 6-methyl-1,3-oxazin-4-ones 3c,d , whereas the unbranched imidate 2b,e gave oxazines 3b,e and pyrimidines 4b,e (Method A). The reaction of acyl Meldrum's acid 5 with imidate 2 afford 2,6-disubstituted oxazine 3, though the alkylimidate with acetyl Meldrum's acid yielded 3 and 5-acetyl-1,3-oxazine-4,6-dione 8 (Method B). The cylodehydration of acylacetylcarboxamide 13 with acid, such as 70% perchloric acid or fluorosulfonic acid, afforded 1,3-oxazines 3 (Method C).     

Katalytische reaktionen von aminen mit olefinen

Tetramethylethylenediamine (TMED) reacts with ethylene (propene) under the influence of catalytic amounts of alkyllithium to give dimethylvinylamine and dimethylethylamine (dimethylisopropylamine). In competitive reactions alkyl-lithium and the amides formed by this with primary or secondary amines in presence of tetramethylethylenediamine enhance the addition of primary or secondary amines to ethylene more strongly than in the absence of the diamine. The pressures are $\text{1}\text{5}$ to $\text{1}\text{10}$ of those needed when sodium catalysts are used and the temperatures required are 50–100° lower. Dimethylamine but not diethylamine, which however reacts with cycloolefins containing strained double bonds, adds to propene.     

Novel Synthesis of Acylaminomethylene Meldrum's Acids and Their Thermolysis to 4-Methylthio-and 4-Amino-2-aryl-6H-1,3-oxazin-6-ones

Bismethylthiomethylene Meldrum's acid reacts with amides in the presence of potassium hydroxide to afford methylthioacylaminomethylene Meldrum's acid 5. Aminolysis of 5 gives aminoacylaminomethylene Meldrum's acids 7. Thermolysis of 5 and 7 supplies a novel synthetic method of 4-methylthio- and 4-amino-2-aryl-6H-1,3-oxazin-6-ones.     

Reactions of 4-Hydroxy-5-methyl(phenyl)-2-styryl-6H-1,3-oxazin-6-ones with Nucleophiles

4-Hydroxy-5-methyl(phenyl)-2-styryl-6H-1,3-oxazin-6-ones react with hydrazine and phenylhydrazine to give the corresponding 3,5-substituted triazoles. Treatment of the title compounds with ethanol and methanol leads to formation of N-cinnamoylmalonamates. The structure of the products was confirmed by the IR and ¹H and ¹³C NMR spectra.     

5-Acyl-4-amino-2-phenyl-1,3-oxazin-6-ones

Intramolecular cyclization of acyl(ethoxycarbonyl)keteneN-benzoylaminals in boiling Ph₂O gives 5-acyl-4-amino-2-phenyl-1,3-oxazin-6-ones.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1322–1323, July, 1995.This study was financially supported by the Russian Foundation for Basic Research (Grant No. 94-03-08964).     

Photochemische reaktionen von äthern mit 4-methylcinnolin und chinoxalinen

1. 4-Methylcinnoline on irradiation in ethers produces the photoproducts 2–6 by a 1.4 addition of the ethers. 2. Quinoxaline reacts with ethers to produce the quinoxalines 8, 12 and 13 by what appears superficially to be a substitution process. Reaction of 2,3-dimethylquinoxaline with tetrahydrofuran gives as the main product 16 by 1.2 addition, and 2-(t-butyl)-quinoxaline gives the dihydroquinoxaline derivatives 17a, b . Because of the known easy autoxidation of 1,2-dihydroquinoxaline we believe that the intermediate in the photolytic reaction of quinoxaline, yielding 8, 12 and 13 , is also the 1.2 addition product. 3. The mass-spectrometric behaviour of the cinnoline and quinoxaline derivatives has been discussed.     

Synthesis of 4H-1, 3-oxazin-4-onium salts

Chemistry of Heterocyclic Compounds -     

An unexpected preparation of 4-oxo-2H-1,3-benzothiazines

Treatment of compound N,N-(dithiobis(3-chloro-2,1-phenylene)dicarbonylbis (N-cyclopentylglycine)diethyl ester (3) with methanolic sodium hydroxide does not produce the expected hydrolysis product N,N-(dithiobis-(3-chloro-2,1-phenylene)dicarbonylbis (N-cylcopentylglycine) (4) but yields a mixture of compounds 8-chloro-3-cyclopentyl-3,4-dihydro-4-oxo-2H-1,3-benzothiazine-2-carboxylic acid (6) and N-(3-chloro-2-mercaptobenzoyl)-N-cyclopentylglycine (7). This unexpected observation has the potential of a new heterocyclic synthesis method for the 4-oxo-2H-1,3-benzothiazine class of compounds.