Synthesis of polyamides from active 5,5′-isophthaloyldithiobis-2-aryl-1,3,4-oxadiazoles and diamines under mild conditions

As model compounds for determining the potential adaptability of novel leaving group to polyamide synthesis, 2-aryl-5-benzoylthio-1,3,4-oxadiazoles having various electron accepting and donating groups in the oxadiazole unit were successfully prepared from the benzoylation of the corresponding 2-aryl-1,3,4-oxadiazoline-5-thiones under kinetically controlled conditions ( < ?50°C). The aminolyses of all the benzoyl thioesters by aniline afforded quantitative yields of benzanilide at room temperature in a short reaction time. Polycondensations of new active dithioesters, 5,5′-isophthaloyldithiobis-2-aryl-1,3,4-oxadiazoles, with both aliphatic and aromatic diamines occured quite rapidly even at room temperature to form polyamides with reduced viscosities up to 0.41 dL/g. The reactivities of the dithioesters having electron accepting groups such as p-chloro and p-nitro groups, particularly p-nitro groups, toward diamines were much higher than that of the dithioester having no such groups, but the introduction of electron donating p-methyl group had an adverse effect. The effects of reaction conditions such as solvent, temperature, and monomer concentration on the reduced viscosity of polyamides were also investigated. It was found that monomer concentration had a remarkable influence on the molecular weight of the resulting polyamides.     

Synthesis of substituted N-(2,4-dioxo-1,2,3,4-tetrahydroquinazolinyl)benzamides and N-(2-thiono-4-oxo-1,2,3,4-tetrahydroquinazolinyl)benzamides

Substituted N-(2,4-Dioxo-1,2,3,4-tetrahydroquinazolinyl)benzamides ( 3a-g ) and substituted N-(2-Thiono-4-oxo-1,2,3,4-tetrahydroquinazolinyl)benzamides ( 4a-g ) were synthesized in one step from the reaction of methyl anthranilate with 2-aryl-1,3,4-oxadiazolin-5-ones ( 1a-g ) and 2-aryl-1,3,4-oxadiazoline-5-thiones ( 2a-g ), respectively, in m-cresol at 150–160°. Alternative routes leading to the formation of 3a and 4a are also reported.     

5-Aryl-1,3,4-oxadiazoline-2(3H)-thiones in reactions with alkyl haloacetates

The reaction of 5-aryl-1,3,4-oxadiazoline-2(3H)-thiones with alkyl haloacetates has been studied. It was shown that the reaction proceeds to give S-substituted products. The effect of the nature of the substituents in the molecules of both the thiones and the haloacetates on the reaction route and yields has been examined.     

Reaction of 5-aryl-1,3,4-oxadiazole-2(3H)-thiones with chloromethyl alkyl ethers

3-Alkoxymethyl-5-aryl-1,3,4-oxadiazole-2(3H)-thiones were synthesized. The direction of alkylation of 5-aryl-1,3,4-oxadiazoline-2-thiones and their potassium salts was studied relative to the substrate, alkylating agent, solvent, and reaction conditions.Institute of Plant Chemistry, Academy of Sciences of the Republic of Uzbekistan, 7001 70 Tashkent, Uzbekistan. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1249–1252, September, 1999.     

Direction of alkylation of 5-aryl-1,3,4-oxadiazoline-2-thiones

The reaction of potassium salt of 5-(2,4-dichlorophenyl)-1,3,4-oxadiazoline-2-thione with dimethyl sulfate was carried out in water and HMPT. It was shown that the nature of the solvent affects the ratio of the formed products of S- and N-methylation. The alkylation of 5-aryl-1,3,4-oxadiazoline-2-thiones with isomeric butyl chlorides showed that the reaction takes place only with n-butyl chloride with the formation of the corresponding S-butyl-substituted derivative.Institute of the Chemistry of Vegetable Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent 700170. Translated from Khimiya Geterotsikliheskikh Soedinenii, No. 9, pp. 1268–1270, September, 1997.     

Preparation of polymers containing the 1,3,4-oxadiazoline-5-thione structure and their application to the activation of N-protected α-amino acids

Two new monomers with pendent 1,3,4-oxadiazoline-5-thione structures were prepared. Homopolymerization of 2-isopropenyl-1,3,4-oxadiazoline-5-thione (V) and copolymerization with styrene (M₁)(r₁ = 0.02, r₂ = 1.56, Q = 4.12, e = 1.06) were examined. Further, 2-(4-methacryloylaminophenyl)-1,3,4-oxadiazoline-5-thione (VIII) having a phenylcarbamoyl group between the isopropenyl and 1,3,4-oxadiazoline-5-thione ring as a spacer was also synthesized and polymerized. The resultant polymers were allowed to react with N-protected α-amino acids such as Z-AlaOH, Z-LeuOH and Z-PheOH by the DCC method. The polymers containing amino acids thus obtained were reacted with ethyl glycinate to give the corresponding dipeptides in excellent yields without racemization.     

Reactions of α-Halo Ketones with 5-Benzyl- and 5-Phenoxymethyl-2H,3H-1,3,4-oxadiazole-2-thiones

Alkylation of 5-substituted 2H,3H-1,3,4-oxadiazole-3-thiones with -bromo ketones in alkaline solutions yields 5-substituted 2-aroylmethylthio-1,3,4-oxadiazoles; in acidic solutions these compounds re- arrange into 4-aryl-3-arylacetamido-2H,3H-1,3-thiazol-2-ones.     

Interaction of 5-Aryl-1,3,4-oxadiazoline-2(3H)-thiones wth N-Substituted Chloroacetamides

The reactions of some 5-aryl-1,3,4-oxadiazoline-2(3H)-thiones (aryl = phenyl, 4-bromophenyl, 4-methylphenyl, 2,4-dichlorophenyl) with N-alkyl- and N-arylchloroacetamides has been studied. The nature of the substituents in the molecules of the thiones and the chloroacetamides does not affect the direction of the reaction but does affect the yield of the desired products.     

Preparation and properties of polyamides from 2,2′-p-phenylenebis-5-oxazolones with diamines

Novel phenylated polyamides having inherent viscosities in the range of 0.2–0.4 were prepared by the ring-opening polyaddition of 2,2′-p-phenylenebis(4,4-diphenyl-5-oxazolone) with aliphatic diamines in polar aprotic solvents. Similarly, unsubstituted polyamides were obtained from 2,2′-p-phenylenebis-5-oxazolone and both aliphatic and aromatic diamines. The phenylated polyamides were highly soluble in a wide range of solvents including tetrahydrofuran and dioxane, while the unsubstituted polymers showed limited solubility in the solvents. No marked differences in thermal stability between the phenylated and unsubstituted polyamides were noted, and all the polyamides began to decompose at around 250°C in both air and nitrogen.     

Composés sulfurés hétérocycliques. CII. Action de l'hydroxylamine sur les dihydro-1,2 benzothiazine-3,1 thiones-4

Hydroxylamine reacts with 1-alkyl-1,2-dihydro-3,1-benzothiazine-4thiones ( 1 ), giving 1-alky1-3-hydroxy-2,3-dihydro-1H-quinazoline-4-thiones ( 2 ). The same reagent, in neutral medium, converts 1-aryl-1,2-dihydro-3,1-benzothiazine-4-thiones ( 3 ) into 1-aryl-4-hydroxyimino-1,4-dihydro-2H-3,1-benzothiazines ( 4 ). In acidic medium, the same starting materials lead to 1-aryl-3-hydroxy-2-3-dihydro-1H-quinazoline-4-thiones ( 5 ). genrally with some quantity of the isomer 4 . Thiones 2 and 5 , as well as oximes 4 , heated at 200°, decomopose, yielding, in varying proportions, 1H-quinazoline-4-thiones ( 6 or 7 ), 1H-quinazoline-4-ones ( 9 ) and 2,3-dihydro-1H-quinazoline-4-thiones ( 11 ). Reacting with methyliodide, 1H-quinazoline-4-thiones ( 7 ) give 4-methylthioquinazolin-1-ium iodidies ( 12 ) which can be hydrolysed into 1H-quinazolin-4-ones ( 9 ). The latter are also obtained by reacting benzonitrile N-oxide with the corresponding thiones. 1-Aryl-1 H-quinazoline-4-thiones ( 7 ) react readily with nitrogen nucleophiles XNH₂ to give 1-aryl-4-imino-1,4-dihydro-quinazolines diversely substituted on the imino group. While thiones 7 are S- methylated by methyl iodide, the corresponding 1-aryl-1H-quinazolin-4-ones (9), with the same reagent, ungergo a N-methylation, yielding 1-aryl-3-methyl-4-oxo-3,4-dihydroquinazolin-l-ium iodides ( 18 ). Structure have been confirmed by uv, ir and nmr spectra.     

Synthesis and Transformations of 2-R-5-Aryl-5,6-dihydro-7H-[1,2,4]-triazolo[5,1-b][1,3]thiazin-7-ones

A new procedure for preparation of 2-R-5-aryl-5,6-dihydro-7H-[1,2,4]triazolo[5,1-b][1,3]thiazin-7-ones by condensation of 5-R-1,2,4-triazole-3-thiones with 3-arylacryloyl chlorides was developed. The thiazine ring of the [1,2,4]triazolo[5,1-b][1,3]thiazin-7-ones is easily cleaved by treating with ammonia and hydrazine affording amides and hydrazides of 3-aryl-3-(1H-1,2,4-triazol-5-ylsulfanyl)propanoic acids. The latter react with isothiocyanates furnishing carbamoyl thiohydrazides of 3-aryl-3-(1H-1,2,4-triazol-5-ylsulfanyl)propanoic acids that in alkaline media undergo cyclization into 4-aryl-5-[2-(4H-1,2,4-triazol-5-ylsulfanyl)-2-phenylethyl]-2,4-dihydro-3H-1,2,4-triazole-5-thiones.     

UV and MO study on the deprotonation of some 2-aryl-Δ2-1,3,4-oxadiazoline-5-thiones

Substituent effects on the deprotonation processes of a series of 2-aryl-Δ²-1,3,4-oxadiazoline-5-thione (1) derivatives have been studied experimentally as well as theoretically. The acid dissociation constants pK_a have been determined spectrophotometrically in ethanol-water solutions (7.5-92.5%) and vary between 3.76 and 5.80. Semiempirical molecular orbital (MO) calculations (AM1 and PM3) were used for the investigation of the existence of possible tautomeric thione and thiol forms of the studied compounds. Strong correlation between the pK_a values and the deprotonation enthalpies were evaluated.     

Synthesis of heterocycles on the basis of arylation products of unsaturated compounds: XX. Reaction of 2-aryl-1,4-benzoquinones with potassium <Emphasis Type="Italic">O</Emphasis>-butyl carbonodithioate

Reactions of 2-aryl-1,4-benzoquinones with potassium O-butyl carbonodithioate gave the corresponding 7-aryl-5-hydroxy-1,3-benzoxathiole-2-thiones. In some cases, 7-aryl-5-hydroxy-1,3-benzoxathiol-2-ones were also formed.     

Synthesis of polyamides from active N,N′-diacylbis-2-benzothiazolones and diamines under mild conditions

The aminolysis of N-benzoyl-2-benzothiazolone was studied in model systems and was found to give excellent yields of N-substituted benzamides at room temperature. Solution polycondensation of new bisamides, N,N′-adipoylbis-2-benzothiazolone and N,N′-isophthaloylbis-2-benzothiazolone, proceeded fairly slowly with both aromatic and aliphatic diamines at room temperature to yield polyamides having inherent viscosities up to 1.5. Hexamethylphosphoramide was the best polycondensation medium among some polar aprotic solvents for the formation of high molecular weight polyamides. The high reactivity of the N-acyl-2-benzothiazolones was discussed in relation to excellent leaving nature and intramolecular general base catalysis of the benzothiazolone moiety.     

Synthesis and Transformations of 5-Substituted 2-Aryl-7H-[1,2,4]triazolo[3,2-b][1,3]thiazin-7-ones and 2-Aryl-2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4-ones

3-Aryl-1,2,4-triazole-5-thiones react with dimethyl acetylenedicarboxylate and methyl 3-phenyl-propynoate to afford the corresponding 5-substituted 2-aryl-7H-[1,2,4]triazolo[3,2-b][1,3]thiazin-7-ones. Treatment of 2-aryl-2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4-ones with alkalies leads to formation of 3-(benzimidazol-2-ylsulfanyl)-3-arylpropionic acids, their reaction with methyl p-toluenesulfonate yields 1-(3-methyl-2-thioxo-2,3-dihydro-1N-benzimidazol-1-yl)-3-phenyl-2-propen-1-one, and oxidation with hydrogen peroxide gives benzimidazole-2-sulfonic acid and 3-aryl-2-propenoic acids.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 1, 2005, pp. 109–114.Original Russian Text Copyright © 2005 by Britsun, Esipenko, Chernega, Lozinskii.     

Ring-opening reaction of 1,3,4-oxadiazolone and 1,3,4-oxadiazolinethione: Reaction of 2-phenyl-1,3,4-oxadiazolin-5-one and 2-phenyl-1,3,4-oxadiazoline-5-thione with amines

The ring-opening abilities of amines toward 1,3,4-oxadiazolines, 2-phenyl-1,3,4-oxadiazolin-5-one ( 1a ) and 2-phenyl-1,3,4-oxadiazoline-5-thione ( 1b ), were investigated with relation to their basicities or pK_b values. Oxadiazolines 1a and 1b were easily reacted with amines such as benzylamine and aniline, but not with p-nitroaniline, to form the corresponding ring-opening adducts. The reactions of both 1a and 1b with o-phenylenediamine produced benzodiazoles with the liberation of benzoylhydrazide, whereas the reactions with o-aminobenzamide furnished quinazolines with the liberation of ammonia. o-Aminophenol and o-aminothiophenol were also reacted with 1a and 1b both of them giving 1,5-dibenzoylcarbohydrazide from 1a and 1,2-dibenzoylhydrazine from 1b. From the conditions affording the corresponding ring-opening adducts or reaction products, the ring-opening abilities of the amines toward 1a and 1b are in good correlation with the strength of their basicities or pK_b values. The ring-opening of oxadiazolines were proved to occur with anilines. Therefore, the other reactions are also supposed to proceed via the ring-opening steps.     

Reaction of 4-thioxo-1,3-benzothiazines with thiocarbohydrazine: Synthesis and reactivity of 1,3,4-triazolo[3,2-c]quinazoline derivatives

2-Aryl-4-thioxo-1,3-benzothiazines react with thiocarbohydrazide to give the new mesoionic compounds an-hydro 1-amino-5-aryl-2-mercapto-1,3,4-triazolo[3,2-c]quinazolin-4-ium hydroxides. These compounds react with methyl iodide, aldehydes and phenacyl bromides to give 1-amino-5-aryl-2-methylthio-1,3,4-triazolo-[3,2-c]quinazolin-4-ium iodides, 4-arylidenamino-3-(o-aroylamino)phenyl-1H-1,2,4-triazolin-5-thiones and 3-(o-aroylamino)phenyl-6-aryl-7H-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines, respectively. These latter compounds by sequential treatment with methyl trifluoromethanesulphonate and triethylamine lead to 3-(o-aroylamino)-phenyl-6-aryl-1-methyl-7-mercapto-1H-pyrazolo[5,1-c]-1,2,4-triazoles.     

Synthesis of heterocycles. Part VII Synthesis and antimicrobial activity of some 7H-s-triazolo[3,4-b][1,3,4]thiadiazine and s-triazolo[3,4-b][1,3,4]thiadiazole derivatives

The cyclization of 4-amino-5-aryl-3-cyanomethylthio-1,2,4-triazoles II in the presence of concentrated sulfuric acid yields 7H-6-amino-s-triazolo[3,4-b][1,3,4]thiadiazines III . Cyclization of 4-amino-5-aryl-1,2,4-tria-zole-3-thiones I with phenacyl chloride yields 7H-3-aryl-6-phenyl-s-triazolo[3,4-b][1,3,4]thiadiazines IV . Similarly, compounds I condensed with cyanogen bromide, phenyl isothiocyanate and carbon disulfide to give the corresponding cyclized products 6-amino-3-aryl-s-triazolo[3,4-b][1,3,4]thiadiazoles V , 3-aryl-6-phenyl-amino-s-triazolo[3,4-b][1,3,4]thiadiazoles VI and 3-aryl-striazolo[3,4-b][1,3,4]thiadiazol-6(5H)thiones VII , respectively. Also in the presence of phosphoryl chloride, compounds I underwent cyclization with monocarbo-xylic acids and oxalic acid to 3,6-diaryl-s-triazolo[3,4-b][1,3,4]thiadiazole VIII and 6,6′-bis(3-aryl-s-triazolo-[3,4-b][1,3,4]thiadiazoles) IX . The above compounds were screened for their antimicrobial activity.     

Reactions involving the formation and recyclization of heterocycles

The reaction of 5-aryl-1,3,4-oxadiazole-2-thiones with hydrazine and hydrazides proceeds with recyclization of the oxadiazole ring to a triazole ring. Depending on the nature of the aryl residue, adducts of 5-aryl-1,3,4-oxadiazole-2-thiones with hydrazine can be isolated in a number of cases. 6-Aryl-2-methyldihydro-1,2,4,5-tetrazine-3-thiones are formed with methylhydrazine as a result of recyclization.See [1] for communication VIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 905–909, July, 1971.     

A facile retro-ene reaction of 5-(methoxyamino)-3-aryl-1,3,4-oxadiazol-2(3H)-ones

5-(N-Methoxy-N-methyl)amino-3-aryl-1,3,4-oxadiazol-2(3H)-ones 3 undergo a heteroretro-ene reaction in refluxing methanol in which the leaving enophile is formaldehyde. The resulting 5-(methylimino)-3-aryl-1,3,4-oxadiazolidin-2-one 4 may be viewed as a kinetic product which tautomerizes to the more stable 5-(methylamino)-3-aryl-1,3,4-oxadiazol-2(3H)-one 5 as the thermodynamic product. Comparison of calculated reaction energies reveals that the presence of the heterocyclic ring facilitates the retro-ene reaction, but the expulsion of formaldehyde is predicted to be highly exothermic even in its absence.