Synthesis of 4H-1,3-benzoxazin-4-onium salts and 4-H-1,3-benzoxazin-4-ones

Salicylamide and its substituted derivatives react with aliphatic carboxylic acid anhydrides and perchloric acid to give 4H-1,3-benzoxazin-4-onium salts. These same compounds were obtained by acidic cyclization of O- and N-acylsalicylamides. The synthesized salts are converted to 2-substituted 4H-1,3-benzoxazin-4-ones by the action of triethylamine and are hydrolyzed by water to N-acylsalicylamides. The probable reaction scheme is examined.     

Synthesis of 5,6- and 5,7-dichloro-3-methyl-4H-1,4-benzothiazines and their conversion into sulfones

A one pot synthesis of 5,6- and 5,7-dichloro-3-methyl-4H,4-benzothiazines is reported by the condensation and oxidative cyclization of 2-amino-3,4- and 3,5-dichlorobenzenethiols with β-dicarbonyl compounds. The oxidation of 4H-1,4-benzothiazines by 30% hydrogen peroxide in glacial acetic acid has provided the corresponding sulfones. The effect of the conversion of the sulfide linkage to sulfone is discussed. The structure of all the newly synthesized compounds has been confirmed by elemental analysis and spectral studies.     

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.     

Synthesis and reactions of 4H-3,1-benzothiazines

This study is directed towards the synthesis of the pyrrolo[1,2-α]indole skeleton which is the essential ring system of the active antitumor miomycins. To this end a number of fused heterocycles such as benzothiazines, benzoxazines, indoles and quinolines were synthesized. The structures of the new compounds were assigned by ir, ¹H nmr and ms-data.     

Stereoselective one-pot synthesis of substituted (4Z)-2-alkyl-4-benzylidene- 4H-1,3-benzothiazines

Substituted (4Z)-4-benzylidene-2-methyl-4H-1,3-benzothiazines (1). and (4Z)-2-ethyl-4-benzylidene-4H-1,3-benzothiazines (2). were synthesized by direct stereoselective reactions of S-phenyl ethanethioate or S-phenyl propanethioate with substituted benzyl nitriles in the presence of triflic anhydride.     

Synthesis of 1,3-diglycidylimidazolium salts

For the first time, 1,3-diglycidylimidazolium salts were obtained. Their synthesis was accomplished by two routes: the reaction of imidazole with epichlorohydrin in the presence of sodium perchlorate with the subsequent dehydrochlorination of the reaction products with alkalis, and the quaternization of 1-glycidylimidazoles with epichlorohydrin in the presence of salts of strong acids.Institute of Organophysical Chemistry and Carbon Chemistry, National Academy of Sciences of Ukraine, Donetsk 340114. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1062–1066, August, 1996. Original article submitted May 31, 1996.     

Synthesis of 4-oxo-1,3-benz- and naphthoxazinium salts from o-hydroxyarylamides

The acid-catalyzed acylation of primary and secondary o-hydroxyarylamides, the probable reaction scheme, and the possibility of the formation of 4-oxo-1,3-arenooxazinium salts and analogs in the reaction of amides of salicylic, coumaric, and 1-hydroxy- and 3-hydroxynaphthoic acids and their N-alkyl(aryl)derivatives with excess amounts of aliphatic acid anhydrides and 70% perchloric acid, as well as by the acid cyclization of O- and N-mono- and diacyl derivatives of these amides, are examined. Twelve previously unknown 2-alkyl- and 2-styryl-4-oxo-1,3-naphth[3,2-e]-and -[1,2-e]oxazinium perchlorates were synthesized. N-Methyl- and N-benzylamides of 8-acetoxy-1-naphthoic acid are formed instead of the expected peri-cyclic analogs of oxazinium salts in the reaction of 8-hydroxy-1-naphthoic acid anilides with acetic anhydride and perchloric acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1611–1616, December, 1979.Original article submitted May 31, 1978; revision submitted April 2, 1979.     

Synthesis of heterocycles : Synthesis of 4H-1,4-benzothiazines

A new synthesis of fluorinated 4H-1,4-benzothiazines is being reported for the first time, obtained by condensing O-aminobenzenethiol with fluorinated β-diketones. An oxidative cyclisation mechanism, involving an intramolecular nucleophilic attack in an intermediate enamine system is suggested.     

Synthesis of 6-halogenated 4H-1,4-benzothiazines

The synthesis of 6-halogenated 4H-1,4-benzothiazines is reported by the condensation and oxidative cyclization of 4-substituted 2-aminobenzenethiols (I, R = Cl, Br) with β-diketones in presence of DMSO. The ir, nmr and mass spectral studies are included. 4-Substituted 2-aminobenzenethiols were also prepared by an improved and direct method.     

Intermolecular 1,3-dipolar cycloaddition of benzonitrile oxide to 2H-1,3-benzothiazines and hexahydro-4H-1,3-benzothiazine

The thermal [3 + 2] intermolecular cycloaddition of benzonitrile oxide to 2H-1,3-benzothiazines 1a-g and hexahydro-4H-1,3-benzothiazine ( 5 ) gives new types of tricyclic angularly and linearly condensed 1,2,4-oxadiazolo-1,3-benzothiazine-fused nitrogen-bridgehead ring systems 2a-g, 6 .     

Synthesis of some 4-chlorobenzopyrylium salts and their reactions

4-Chlorobenzopyrylium and 4-chloroflavylium salts have been synthesized, and some reactions of benzopyrylium cations of this type have been studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 8, pp. 1028–1030, August, 1970.     

Synthesis of 4-ethoxycarbonylmethyl-, 4-N-phenylcarbamoylmethyl-, and 4-carboxymethyl-1,3-dithiole-2-thiones and the corresponding 1,3-dithiolium salts

A method for the preparation of 4-ethoxycarbonylmethyl-, 4-N-phenylcarbamoylmethyl-, and 4-carboxymethyl-1,3-dithiole-2-thiones and the corresponding 1,3-dithiolium salts from -bromoacetoacetic ester, -bromoacetoacetanilide, and sodium tertbutyltrithiocarbonate was developed. The compounds were characterized by their IR and PMR spectra.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 180–183, February, 1984.     

Synthesis of substituted 2- and 4-carboxypyrylium salts

Modified methods for the synthesis of substituted 2- and 4-carboxypyrylium perchlorates and the necessary diphenacylacetic acids are proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 162–166, February, 1981.     

Synthesis of 2-amino-5-chloro-3-(trifluoromethyl)benzenethiol and conversion into 4H-1,4-benzothiazines and their sulfones

The synthesis of 2-amino-5-chloro-3-(trifluoromethyl)benzenethiol was achieved by hydrolytic cleavage of 2-amino-6-chloro-4-(trifluoromethyl)benzothiazole which was prepared by cyclization of 4-chloro-2-(trifluoromethyl)phenylthiourea by bromine in chloroform, the phenylthiourea was prepared by the reaction of 4-chloro-2-(trifluoromethyl)aniline with ammonium thiocyanate in hydrochloric acid. Condensation and oxidative cyclization of 2-amino-5-chloro-3-(trifluoromethyl)benzenethiol with β-diketones/β-ketoesters provided 4H-1,4-benzothiazines. Fluorinated sulfones were obtained by oxidation of the corresponding benzothiazines with 30% hydrogen peroxide in glacial acetic acid. The structures of the newly synthesized compounds were confirmed by spectral studies.     

Ring-closure reaction of N-arylthiomethylaroylamides to 1,3-benzothiazines

N-Arylthiomethylaroylamides substituted with an electron-donating group in the meta position undergo two-directional cyclization in the presence of phosphorus oxychloride to give both positional isomers of the 4H-1,3-benzothiazine derivative. The structures of the products were confirmed by ¹H and ¹³C nmr spectroscopy. Mixed ring-closure reactions of several N-arylthiomethylaroylamides 3, 6, 9, 13 have shown that these conversions are introduced by a proton-catalyzed intermolecular rearrangement.     

Cycloaddition reactions of 1,3-benzothiazines - 6. Reactions of 1,3-benzothiazine derivatives with substituted acetyl chlorides

6, 7-Dimethoxy-2$\text{H}$-l,3-benzothiazine derivatives ($\text{1}$, $\text{8}$) react with substituted acetyl chlorides to give angularly condensed β -lactams ($\text{3a}$-$\text{d}$, $\text{10}$, $\text{11}$). The $\text{cis}$ compound $\text{11}$ was epimerised to the $\text{trans}$ derivative $\text{12}$. From the interaction of 2-phenyl-6,7-dimethoxy-4$\text{H}$-1,3-benzothiazine ($\text{7}$) and α -chloro-phenylacetyl chloride two stereoisomeric β -lactam derivatives ($\text{9a}$, $\text{b}$) were isolated, whereas in the other cases studied the reactions leading to β -lactams proved to be stereospecific. Analogous reactions of $\text{4}$-methyl-6,7-dimethoxy-2$\text{H}$-l,3-benzothiazine ($\text{5}$) furnished the enamides $\text{6a}$,$\text{c}$, $\text{d}$. Structures of the new compounds and configurations of the diastereomers were elucidated by IR and NMR spectroscopy.