Mohamed T. Omar

The behaviour of N,N-disubstituted 5-arylmethylidene-2-aminothiazole-4(5H)-ones towards cyclic CH acids and ethyl cyanoacetate

N,N-Disubstituted 5-arylmethylidene-2-aminothiazol-4(5H)-ones reacted with uracil, dimedone and ethyl cyanoacetate to give adducts as a result of addition at the β-terminal of the azomethine moiety and/or addition at the β-carbon of the α,β-unsaturated carbonyl system.

The (E)/(Z)-ratio in the reaction of 5-(2-aryl-2-oxoethyl)-2-thioxo-4-oxo-1,3-thiazolidines with bromine

Summary3-Aryl-, 3-benzyl-, and 3H-5-(2-aryl-2-oxoethyl)-2-thioxo-4-oxo-1,3-thiazolidines3a–h react with bromine in acetic acid solution to give mixtures of the respective 5-aroylmethylene (E) and (Z) diastereomeric derivatives5 and6. They contain more than 85% of the (E)-diastereomers along with some pure isomers. The intermediacy of the 5-bromo derivatives4 is proven and a plausible route of the reaction is presented. Structures of compounds3–6 are evidenced by analytical and spectral data.Zusammenfassung3-Aryl-, 3-Benzyl- und 3H-5-(2-Aryl-2-oxoethyl)-2-thioxo-4-oxo-1,3-thiazolidine3a–h reagieren mit Brom in essigsaurer Lösung zu Gemischen der entsprechenden diastereomeren 5-Arylmethylen-Derivate ((E) und (Z))5 und6. Sie enthalten mehr als 85% des (E)-Diastereomeren. Die intermediäre Natur der 5-Brom-Derivate4 wird bewiesen; ein Reaktionsweg wird vorgeschlagen. Die Strukturen der Verbindungen3–6 werden durch analytische und spektroskopische Daten abgesichert.

Reactions of N,N-Disubstituted 5-Arylmethylidene-2-amino-thiazol-4(5H)-ones with CH Acids

Summary. N,N-Disubstituted 5-arylmethylidene-2-aminothiazol-4(5H)-ones reacted with diethyl malonate, ethyl benzoylacetate, acetylacetone, or cyclopentadiene in refluxing toluene and in presence of powdered sodium to give the respective 5-arylmethylidene-2′-amino-2,5′-bithiazolylidene-4,4′-dione derivatives in moderate yields. 5-Benzylidene-2-morpholin-4-yl-2-thiazol-4(5H)-one reacted with malononitrile in toluene and in presence of powdered sodium under mild conditions to afford the 1:1 adduct, benzylmalononitrile, and 2-morpholin-4-yl-2-thiazol-4(5H)-one. However, similar treatment of 5-(4-methoxyphenylmethylidene)-2-morpholin-4-yl-2-thiazol-4(5H)-one with malononitrile yielded the 2,5′-bithiazolylidene-4,4′-dione derivative together with 4-methoxyphenylmethylidene malononitrile. Treatment of 5-benzylidene- and 5-(4-methoxyphenylmethylidene)-2-morpholin-4-yl-2-thiazol-4(5H)-ones with 3-phenyl-4-oxo-2-thioxo-1,3-thiazolidine in refluxing toluene and in presence of powdered sodium produced 5-arylmethylidene-3-phenyl-4-oxo-2-thioxo-1,3-thiazolidines in good yields. The structures of all products were deduced from microanalytical and spectroscopic data, mechanistic details are discussed.

ADDUCTS FROM 2, 3-DIARYL-5-PHENYLMETHYLENE-4-OXO-1, 3-THIAZOLIDINE-1-OXIDES

Abstract 5-Phenylrnethylene-2, 3-diaryl-4-oxo-1,3-thiazolidine-1-oxides 2 which synthesised via peracetic acid oxidation of the respective 1, 3-thiazolidines 1 reacted with benzylamine and Grignard reagents to afford the respective 5-α-substituted benzyl-2, 3-diaryl-4-oxo-1,3-thiazolidine-l-oxides 3 and 4. Structures of 3 and 4 were based on analytical and spectral evidence.

REACTIONS OF 5-SUBSTITUTED-2-THIOXO-4-OXO-1,3-THIAZOLIDINES WITH 4-METHOXYPHENYLAZIDE

Abstract 4-Methoxyphenylazide cycloadds to the thiono function and undergoes nucleophilic attack at other electrophilic centers of 5-benzoylmethyl-(1a) and E,Z-5-(4-bromobenzoylmethylene)-(E,Z-2b) -2-thi-oxx-4-oxo-1,3-thiazolidines in non site selective reactions to afford variety of products. With la, the attack at the thiono as well as the hetero-ring carbonyl functions leads to the 5-benzoylmethylene-2-(4-methoxyphenylimino)-derivative (3) and the ring fission product 2–4. Similar treatment of E,Z-Zb gives a mixture of the respective E,Z-2-(4-methoxyphenylimino)-derivative (E,Z-5) containing 80% of the Z-configurated isomer (Z-5) and the ring enlarged thiazinonethione derivative (6), due to the attack at the thiono and exocyclic double bond functions, respectively. Rationalizations for the above mentioned conversions are given. Structures of all products are evidenced by microanalytical and spectral data.

(E)-, (Z)-Interconversion in 3-aroylmethyl-5-arylmethylene-2,4-dioxo-1,3-thiazolidines

SummaryThe (E)-, (Z)-interconversion in 3-aroylmethyl-5-arylmethylene-2,4-dioxo-1,3-thiazolidines is simply achieved upon treating with phenylhydrazine in acetic acid solutions. Configurational assignments are based on1H-NMR spectral data.ZusammenfassungDie (E)-, (Z)-Interkonversion in 3-Aroylmethyl-5-arylmethylen-2,4-dioxo-1,3-thiazolidinen wird durch Behandlung mit Phenylhydrazin in essigsaurer Lösung erreicht. Die Zuordnung von Konfigurationen basiert auf1H-NMR-Daten.

Novel synthesis of thieno[2,3-d] and 1,2-dithiino[4,5-c] Thiazoles

Thionation of 3-substituted-5-(2-aryl-2-oxoethyl)-2-thioxo-4-oxo-1,3-thiazolidines 1a-e either with tetraphosphorous decasulfide or with Lawessons reagent in xylene affords the respective 3-substituted-5-aryl-2,3-dihydro [2,3-d] 1,3-thiazole-2-thiones 2a-e . However, thionation of 1f affords 3-(3-methylphenyl)-6-(4-ethylphenyl)-2-thio-2,3-dihydrothiazolo[4,5-c]1,2-dithin 3 . The structure of the synthesized compounds were supported by microanalytical and spectral evidence. A rationalization for the route of conversion was also given.

Stereochemistry of the [4 + 2] cycloaddition reactions of 5-arylmethylene-2,4-dithioxo-1,3-thiazolidines with acrylonitrile, 1-ethoxy-3-phenyl- E -2-propen-1-one and 3-phenyl- E -2-propen-1-one

The [4 + 2] cycloaddition reactions of 5-arylmethylene-2,4-dithioxo-1,3-thiazolidines with different dienophiles and separation of pure stereoisomeric products are reported.