Nouvelles synthèses de thiéno[3,2-c] - et thiéno[2,3-c]pyridines

A new method for the synthesis of thieno[2,3-c]-and [3,2-c]-pyridines and of their tetrahydro derivatives is described. The process is based on some modifications of the Pomeranz-Fritsch reaction leading to isoquinolines.     

Furannes et pyrroles disubstitués en 2,3. XVI synthèse de furo[3,2-c]pyranones-4 et nouvelle voie d'accès aux furo[3,2-c]pyridines

Treatment of 4-hydroxy-6-methylpyran-2-one with chloracetalhyde in basic aqueous medium gave 6-methylfuro[3,2-c]pyran-4-one. This compound reacted with ammonium hydroxide and some primary amines to form the corresponding N-substituted furo[3,2-c]pyrid-4-ones which may also be obtained from 4-hydroxy-α-pyridones. Furo[3,2-c]pyran-4-one was acylated at the 2 position and 4-chloro-6-methylfuro[3,2-c]pyridine easily gave 4-substituted derivatives by displacement of the halogen atom.     

Aza-2-diènes-1,3 3. Nouvelles voies d'accès à des amino-2-pyrazines substituées

2-Aza-1,3-dienes. A New Approach to Substituted 2-Aminopyrazines Treatment of enamines by tosylated isonitrosomalono derivatives gives access to 5-dialkylamino-1, 1-dicyano 2-aza-1,3-dienes (or 1-methoxycarbonyl analogous) which are precursors of various regiospecific 5,6-substituted 2-amino-3-cyano (or methoxycarbonyl) pyrazines. Some examples of utilisation of these intermediates for synthesis of lumazines, pteridines, and other bicyclic skeletons are described.     

Synthèse et étude de modèles de NADH à noyaux accolés en série pyrrolo[2,3-b] et [3,2-b]pyridines

Pyrrolo[2,3-b] and [3,2-b]pyridines derivatives, precursors for annealated NADH models have been prepared. Several methods for building a pyridinic annealates ring have been used starting from 2- or 3-aminopyrrole. The corresponding dihydropyridine structure leads to highly reactive NADH models compounds and are very much more stable than common models.     

Action de réactifs nucléophiles sur les phényl-5 thiéno[3,2-b]pyrannone-7 et phényl-2 benzo[b]thiéno[3,2-b]pyrannone-4

Reactions of 5-phenylthieno[3,2-b]pyran-7-one, 2-phenylbenzo[b]-thieno[3,2-b]pyran-4-one and the corresponding thiones with sodium ethylate, guanidines, hydrazines and amines are described and compared to those observed with benzopyranones.     

Synthèse et étude physicochimique des 1,2,4-triazolo[4,3-a]-pyridines et des 1,2,4-triazolo[2,3-a]pyridines

The synthesis of 1,2,4-triazolo[4,3-a] and [2,3-a]pyridines 7, 8 was achieved by cyclization of 2-hydrazino-8-nitropyridine 3a with formic acid. The 4,5,6,7-tetrahydro-1,2,4-triazolo[2,3-a]pyridine 13 and 8-amino-1,2,4-triazolo[2,3-a]pyridine 9 were obtained by catalytic hydrogenation. The reduction of triazolo pyridine 8 using stannous chloride led to the intermediate compound 10 which with acetic anhydride afforded 8-acetylamino-5-chloro-1,2,4-triazolo[2,3-a]pyridine 10a . The structure of the derivatives was determined by ¹H-nmr (DMSO-d₆).     

Thiénopyrimidines VIII. Etude des thiéno[2,3-d] pyrimidinethiones

Substitution and addition reactions of thieno[2,3-d] pyrimidine-thiones have been studied. These reactions led to S- and N- substituted derivatives whose structure was established by the synthetic routes as well as by the ir and pmr spectra.     

Nouvelle méthode d'accès aux benzo[h]furo[3,2-c]quinoléines,analogues isostériques des benzo[c]phénanthridines

A convenient synthesis of the benzo[h]furo[3,2-c]quinoline ring is reported. Hydrogenation of dienic adducts 5 gives comppounds 6. Successive pyrolysis and alcaline hydrolysis of 6 provide diacids 9 which in the presence of anhydrous ammonium acetate and acetic acid undergoes intramolecular cyclisation to give benzo[h]furo[3,2-c]quinolone derivatives 12. The modulation of the 7-carboxy group and introduction of amino groups in the 6 position are then realized.     

Synthesis and reactions of 2,3-dimethylfuro[3,2-c]pyridines

Summary A number of substituted 2,3-dimethylfuro[3,2-c]pyridines was synthesized. 3-(4,5-Dimethyl-2-furyl)propenoic acid (1) was converted to the acid azide2, which in turn was cyclized to give 2,3-dimethyl-5H-furo[3,2-c]pyridine-4-one (3) by heating at 240°C in Dowtherm. The pyridone3 was chlorinated with phosphorus oxychloride to give4, which was reduced with zinc and acetic acid to 2,3-dimethylfuro[3,2-c]pyridine (5). Treatment of4 with several secondary heterocyclic amines led to compounds6a–6c. Reaction of pyridone3 with phosphorus pentasulfide rendered the thione7, which was methylated to8a. The 4-methoxy derivative8b was obtained from4 with sodium methoxide. 2,3,5-Trimethylfuro[3,2-c]pyridine-4-one (9) was obtained by reaction of3 with methyl iodide.Dedicated to Professor Dr.Fritz Sauter on the occasion of his 65th birthday     

Spectres photoélectroniques de divers thiéno[2,3-b] thiophènes

Photoelectron spectra of thieno[2,3-b]thiophene and its mono halogeno and mono methyl derivatives have been analysed. The proposed assignments were confirmed by the effects of di, Iri and tetra substitutions and are in good agreement with a CNDO/S calculation.     

Thiényl- et séléniénylthiocyanates et sélénocyanates. 4. Synthèses de thiéno[2,3-d]thiazoles,de thiéno[2,3-e]thiazines et de quelques analogues sélénophéniques

Nucleophilic aromatic substitution of 3-bromo-2nitrothiophene and selenophene by thiocyanate and selenocyanate ions in dimethylsulfoxide yields 3-thienyl-and 3-selenienylthicoyanates and selenocyanates. After reduction of the nitro group, the amino derivatives undergo cyclizatrion to thieno[2,3-d]thiazoles and seleno [2,3-d]thiazoles. Also, 4H-2,3-dihydro-3-oxothieno[2,3-e]1,4-thiazine and its selenophene analog have been obtained.     

Indoles polycycliques. I. Synthèse de dérivés oxo-6 du benzo[a]pyrano-[4,3-b] indole et de l'indolo[3,2-c] quinoléine à partir d'acides aryl-2 indole carboxyliques-3

The tetracyclic indole derivatives were prepared by lactonisation of 1-methyl-2-(2-hydroxyphenyl)indole-3-carboxylic acid or by reductive cyclisation of 1-methyl-2-(2 nitrophenyl)indole-3-carboxylic acid, respectively. These acids were obtained, in good yields, by alkaline hydrolysis of 1-methyl-2-aryl-3-trifluoroacetyl-indoles. This last synthetic method seems of general use to prepare 2-arylindole-3-carboxylic acids in which the pyrrole nitrogen atom is substituted.     

Pyrrolo[1,2-a]thiéno[2,3-e]pyrazine. Etude chimique de la dihydro-4,5 oxo-5 pyrrolo[1,2-a]thiéno[2,3-e]pyrazine

The 4,5-dihydropyrrolo[1,2-e]pyrazin-5-one (1) exhibits lactam-lactim tautomerism. N-Electrophilic substitutions could be achieved via the intermediate of the substitutions could be achieved via the intermediate of the sodium salt la. The 5-chloropyrazine 11 obtained by chlorodehydroxylation of pyrazinone 1 allowed nucleophilic substitution. Thionation of the pyrazinone 1 afforded the thioxopyrazine 27 wich gave studied and the tautomerism of the hydrazinopyrazine 14 and its derivatives are discussed in terms of hydrazone and azine structures     

The synthesis and chemical reactivity of thieno[2,3-c]- and thieno[3,2-c] pyridines

The syntheses and reactions of various thieno[2,3-c]- and thieno[3,2-c] pyridines are described. Molecular orbital calculations were performed on thieno[2,3-c]pyridine (1) in order to determine the most susceptible sites to electrophilic and nucleophilic attack. Superdelocalizability values, S_r- are reported for each position in this molecule to give relative orders of reactivity towards the two types of reactions. Electrophilic attack was found to occur experimentally at C-3 in all the thienopyridines studied. Peracid oxidation of thieno[2,3-c]- and thieno[3,2-c]pyridines produced only the N-oxide. The lack of reactivity of certain thienopyridines under Vilsmeier formylation and Friedel-Crafts acetylation conditions was related to their basicities. The dissociation constants of various thienopyridinium salts are reported.     

A concise synthesis of functionalized 2,3-dihydrofuro[3,2-b], [3,2-c], and [2,3-b]pyridines

A strategy for the efficient and rapid one-pot synthesis of 2-aryl-2,3-dihydrofuro[3,2-b], [3,2-c], and [2,3-b]pyridines from readily available o-nitropicolines and aromatic aldehydes is described. The key transformation involves reaction of o-nitropicolines with aromatic aldehydes in the presence of TBAF and Hünig's base giving rise to functionalized products having molecular complexity suitable for further manipulation.     

Quelques réactions nuclé ophiles et électrophiles de la thiéno[2,3-b]pyrazine. Comparaison de sa réactivite avec celles de thiéno diazines et de la thiényl-2 pyrazine dans le cas de la nitration

We studied the action of nbutyllithium, the action of chlorine and the action of nitric acid in sulfuric acid medium on thieno-[2,3-b]pyrazine, These reactions led us to comparethe behaviour of thieno[2,3-b]pryazine with that of thieno[2,3-d]pyrimidine and of thieny1-2pyrazine under the same consitions.