Etude dans la série des radicaux hétérocycliques. Partie XV. Décomposition aprotique de l'amino-6-éthyl-2-benzothiazole dans des substrats aromatiques et hétéroaromatiques: préparation des mésityl-6- et furyl-6-éthyl-2-benzothiazoles,des sels quaternaires et des spiropyrannes correspondants

Study of heteroaromatic radicals. Part XV .

1 Partie XIV: cf. [1].

Aprotic decomposition of 6-amino-2-ethylbenzothiazole in aromatic and heteroaromatic substrates: preparation of 6-mesityl- and 6-furyl-2-ethylbenzothiazoles and of the corresponding quaternary salts and spyropyrans In the presence of excess isopentyl nitrite in aprotic solvent, the 6-amino-2-ethyl-benzothiazole leads to 6-aryl- and 6-heteroaryl-2-ethylbenzothiazoles 1 to 14 in ca. 20–50% yield (Scheme 1, Table 1). The 2-ethyl-6-benzothiazolyl radicals generated during these reactions exhibit a weak electrophilic character (Table 2). Preparatively this method has been applied to the synthesis of 6-mesityl- and 6-furyl-2-ethylbenzothiazoles 6 and 7 , which were used to prepare the corresponding quaternary salts 15 , 16 and the spiropyrans 19, 20 (Scheme 4).     

Synthèse photochimique de biaryles et hétérobiaryles à partir d'aryl-et hétéroarylamines,d'un nitrite d'alkyle et d'un substrat aromatique ou hétéroaromatique

Photochemical synthesis of biaryls and heterobiaryls from aryl and heteroarylamines, alkylnitrite and aromatic or heteromatic substrates The photochemical reaction of aromatic and heteroaromatic amines with excess t-butyl nitrite in aromatic solvents (benzene, p-xylene, mesitylene) and in hetero-aromatic solvents (furan, thiophene) leads to biaryls or heterobiaryls. t-Butyl nitrite is more convenient than isopentyl nitrite which gives by-products. This new method has been used to synthesize 28 compounds in 17 to 60% yield.     

Etude en série triazénique. IV. Synthèse et réactivité d'aryl-3-(diméthyl-3,4-isoxazolyl-5)-1-triazènes et d'arylazo-4-diméthyl-3,4-isoxazolones-5

Synthesis and reactivity of 3-aryl-1-(3,4-dimethyl-5-isoxazolyl)-triazenes and 4-arylazo-3,4-dimethylisoxazol-5-ones According to the experimental conditions and the nature of the substituents on the aromatic ring, aryldiazonium salts react with 5-amino-3,4-dimethylisoxazole ( 3 ) leading to either 3-aryl-1 (3,4-dimethyl-5-isoxazolyl)-triazenes ( 1A ) or 4-arylazo-3,4-dimethylisoxazol-5-ones ( 4 ). Analyses of the products resulting from thermal decomposition of these triazenes in aromatic substrates and in DMSO and their behaviour in acidic medium show that it is essentially the arylazo form 1B which is reactive.     

Etude dans la serie des radicaux heterocycliques—X : Reaction de pseudo-gomberg: Décomposition en milieu protique et aprotique d'amino-2 thiazoles en série pyridinique. Nouvelle voie d'accès aux thiazolylpyridines.

The decomposition of 2-aminothiazoles in the presence of isoamylnitrite has been studied with pyridine substrates. GLC/MS allows the identification of thiazolylpyridines and by-products. An important solvation effect and the electrophilic nature of thiazol-2-yl radicals in strongly basic substrates have been demonstrated. The greater reactivity of di or trimethyl pyridines can be exploited to synthesize new thiazolylpyridines having interesting insecticidal properties. In acidic media, contrary to what is observed with other radical sources, these substrates show a poor reactivity relative to benzene, which may be related to the cage decomposition mechanism of diazoamino compounds.     

Etudes RMN en série hétérocyclique—XIII:Spectres des azoles dans l'acide sulfurique

NMR spectra of benzimidazole, indazole, 1-phenylimidazole, 1-phenylpyrazole and some of their methyl derivatives have been studied in sulphuric acid solution in order to determine the coupling constants with the protons bonded to nitrogen atoms.     

Réarrangements 1,3 en série hétérocyclicque. II. Synthese d'alcoxy-5 et aryloxy-5 phényl-2 oxadiazoles-1,3,4

The 5-Chloro-2-Phenyl-1,3,4-oxadiazole has been prepared in fair yield. This product is a convenient starting material for the synthesis of O-alkylated or O-arylated derivatives of the 5-hydroxy-2-phenyl-1,3,4-oxadiazole.     

Nouveaux exemples de radicaux libres stables de dérivés hétérocycliques de sucres. Communication préliminaire

Some more examples of stable free radicals of carbohydrate heterocyclic derivatives 2-Glycosyl-4,4,5,5-tetramethylimidazoline- 3-oxide-1-oxyls and 2-glycosyl-4,4,5,5-tetramethylimidazoline 1-oxyls have been prepared in nine carbohydrate series, which proves the generality of the method. The hyperfine coupling constant between the free electron and the α-proton of the glycosyl group is never very large (0-2.3 G) but a correlation between its value and the structure of the aglycone has been noted. Free radicals of that type, stable in aqueous solutions, are potentially interesting for biological studies.     

Etudes photochimiques en série hétérocyclique. V. Mise en évidence d'oxazoles par photooxydation de thiazoles

Formation of oxazoles as by-products of photooxydation of thiazoles In the presence of air, light (high pressure mercury lamp) and iodine as sensitizer, benzene solution of arylthiazoles 2 , 3 and 13 (see scheme 1) were converted into a mixture of photoisomers and aryloxazoles (see scheme 2). Upon shorter times of irradiation under oxygen in chloroform containing methylene blue as a sensitizer 2,4,5-triphenylthiazole (7) is converted in 2,4,5-triphenyloxazole. Under usual photooxidation conditions, in methanol as solvent, most of arylthiazoles studied gave a mixture of nitriles, amides, acids esters and diketones. In the case of thiazole 7 , the corresponding oxazole was also found. A possible mechanism for the photochemical oxidation of arylthiazoles to aryloxazoles, via 2,5- and 4,5-endo-peroxides, may be proposed (see schemes 5 and 6).     

Etude de l'oxydation de tétrahydroisoquinoléinols-4 diméthoxylés en 6,7 ou 7,8, et sur la réactivité du carbonyle de la tétrahydroisoquinolone-4 diméthoxylée en 6,7

Preparation of the tetrahydroisoquinolin-4-ols indicated in the title and their oxidation by different reagents (chromic anhydride, NBA, dimethylsulfoxide, Oppenauer oxidation) is reported. Only the last reaction led to the title compounds, while the other reagents (except NBA) yielded 1,2,3-trioxotetrahydroisoquinoline. Furthermore, the reactivity of 6,7-dimethoxytetrahydroisoquinolin-4-one was examined towards different carbonyl reagents.     

Synthèse d'hydroxyspirocétals insaturés et hétérocyclisation en méthyl-5 trioxa-2,6,11 tricyclo[5.3.1.01.5]undécane

The photochemical irradiation of unsaturated ketoacetals 4 gives unsaturated hydroxyspirocetals 6 . The mixture of these stereoisomers yields by thermal or ionic treatment a trioxatri-cyclo compound 7 .     

S-Alkylation en série hétérocyclique par catalyse par transfert de phase: thioalkyl-2-thiazoles,thioalkyl-2-Δ-4-thiazolines et thioalkyl-2-benzothiazoles

S-Alkylation in heterocyclic serie by phase transfer catalysis: 2-alkylthiothiazoles, 2-alkylthio-Δ-4-thiazolines and 2-alkylthiobenzothiazoles Some Δ-4-thiazoline-, thiazolidine-, and benzothiazoline-2-thiones have been S-alkylated by phase transfer catalysis; yields averaged 80 to 90%. With halogenated heterocyclic compounds of poor reactivity, the main reaction consisted in a dequaternization of the catalyst by the thiones acting as nucleophiles.     

Structure et synthèses nouvelles dans la série des amino-4 dihydro-5,6 méthyl-6 pyrones-2

Primary and secondary amines react with 4-hydroxy-5,6-dihydro-Z-pyrones at position 4, and not at position 2 as previously indicated. However, a new series of compounds is obtained by this reaction, some of them exhibiting therapeutic properties. Reactivities of dihydropyrones and pyrones are compared.     

Etude des voies d'accès aux aminométhyl benzo[g]isoquinoléinediones-5,10. Mise en évidence d'une substitution anormale au cours de la réaction de Bischler-Napieralski en série diméthoxy-1,4 naphthalène

Under the conditions of the Bischler-Napieralski reaction the cyclization of 2-(1,4-dimethoxy and 1,4,8-trimethoxynaphthyl)ethylacetamides derivatives take place essentially at the 1 position by substitution of the 1-methoxy group. Nevertheless, 1-aminomethyl-9,10-azaanthraquinones are accessibles by condensation of 1-aminomethylisoquinoline-5,8-diones with a 1,4-diacetoxy-1,3-butadiene.     

Etudes RMN en série hétérocyclique. XV—Résonance Magnétique Nucléaire de 1H et de 19F de quelques fluoro-2 benzothiazoles

Chemical shifts and coupling constants of five 2-fluorobenzothiazoles 6-substituted by Me, H, F, Cl and NO₂ are given. A large cross-ring coupling constant (J₂₆ = 10·4 Hz) is found in the 2,6-difluorobenzothiazole.     

Réactivité d'analogues bihétérocycliques du phénanthrène,vis-à-vis des agents d'acétylation et de lithiation

The influence of annelaction and of the heteroatom upon the reactity of some haterocyclic analogus of phenanthrene with a pyrrole nucleos was tested toward acetylation and lithiation. If methy-l[1]benzofuro-[3,2-b]pyrrole was acetylated only in the 2-position, the sulfer and selenious analogues with [3,2-b] and [2,3-b] annelarion were acetylated in the -2 and -3 position. No reaction at all or only with poor yield (in the oxygenated series) was observed with butyllithium except on the case of l-methyl[1]benzoselenono[2,3-b]pyrrole, where the opening of the selenophene nucleos gives, after carbonation and action of diazomethane, l-methyl-2-methoxycarbony 1-3-(o-methylselenophenyl) pyrrole.     

Nouvelle voie de synthèse des dérivés de l'ellipticine et analogues alcaloïdes à activité antitumorale

A new snythesis of 6H-pyrido[4,3-b]carbazoles is described starting from substituted cyclohexanones involving the combination of Borsche's carbazole preparation and Cranwell and Saxton's ellipticine synthesis where the starting materials are easily available. The dehydrogenation step is accomplished at an early stage. In some cases (11-desmethyl ellipticines derivatives), 7H-pyrido[3,4-c]carbazoles were also obtained.     

Etude du couplage 2J(N15?H) en série hétérocyclique. Application à la détermination des constantes d'équilibres prototropiques rapides

The fast tautomeric equilibrium of (N¹⁵)-4-phenylisoxazolin-5-one ( 2 ) has been investigated by a study of ²J(N¹⁵? H₃) coupling. Comparison of the observed values for 2 and for the two fixed forms (N¹⁵)-2-methyl-4-phenylisoxazolin-5-one ( 3 ) and (N¹⁵)-4-phenyl-5-methoxyisoxazol ( 4 ) indicates a considerable amount of enolic type structure for 2 in basic media.     

Furannes et pyrroles disubstitues en 2,3. XVII. Structure des composés formés par eyanuration des halogénométhyl-2 méthoxycarbonyl-3 et −5 furannes

Treatment of methyl 2-bromomethylfuran-3-carboxylate with potassium cyanide yielded methyl 2-cyanomethylfuran-3-carboxylate, methyl 2-methyl-5-cyanofuran-3-carboxylate and two unusual products which appeared by nucleophilic substitution of the activated methylene group of the preceding furylacetonilrile. Products from the cyanide displacement reaction of methyl 5-chloromethylfuran-2-carboxylate are formed in the same way and their previously described formulas are corrected. On the other hand, it was pointed out that phosphorus oxychloride-pentachloride transformation of 2-cyanomethylfuran-3-carboxylic acid leads to 4,6-disubstituted furo[3,2-c]pyridines.     

Réactions de Friedel et Crafts de dérivés aromatiques sur les composés dioxo-1,4,2,3-non saturés. IV. Réactions des hydroxy-5-ouchloro-5-diméthyl-3,5- ou diméthyl-4,5-dihydro-2,5-furannones-2

Friedel-Crafts reactions of aromatic derivatives with 1,4-dicarbonyls 2,3-éthylenic compounds. Part IV. Reactions of 5-hydroxy or 5-chloro 3,5-dimethyl or 4,5-dimethyl 2 (5 H) furanones We studied the Friedel-Crafts reactions of 2-(5H)-furanones. In the presence of sulfuric acid and of an aromatic derivative, 5-hydroxy- or 5-chloro-5-methyl-2-(5H)-furanones with one methyl group either in the 3 position, or in the 4 position generally give the corresponding 5-aryl-2-(5H)-furanones, while with aluminium chloride, it is possible to obtain, when a reaction takes place, isomeric 1H-indenecarboxylic acids. However, in a particular case, an addition to the substrate's double bond is observed. The 3-aryl-5-hydroxy-tetrahydrofuran-2-one obtained is methylated in two ways and gives either a cyclic product, or a linear one. In two cases tautomerism between 1H-1-indenecarboxylic acid and 1H-3-indenecarboxylic has been shown by ¹H-NMR.