Thermochemical study of the trans- and cis-isomeric forms of 4-(4-methoxystyryl)pyridine N-oxide

The trans and cis form of 4-(4-methoxystyryl)pyridine N-oxide were studied. The spectral characteristics of cis-4-(4-methoxystyryl)pyridine N-oxide were determined in acetonitrile. The melting and thermal decomposition processes of the trans and cisforms of 4-(4-methoxystyryl)pyridine N-oxide were studied by thermochemical methods. It was establish that the thermal decomposition of 4-(4-methoxystyryl)pyridine N-oxide begins with the cleavage of the bond between the pyridine and benzene rings.

     

Furopyridines. XVII . Cyanation,chlorination and nitration of furo[3,2-b]pyridine N-oxide

The N-oxide 2 of furo[3,2-b]pyridine ( 1 ) was cyanated by the Reissert-Henze reaction with potassium cyanide and benzoyl chloride to give 5-cyano derivative 3 , which was converted to the carboxamide 4 , carboxylic acid 5 , ethyl ester 6 and ethyl imidate 8 . Chlorination of 2 with phosphorus oxychloride yielded 2-9a , 3- 9b , 5- 9c and 7-chloro derivative 9d . Reaction of 9d with sodium methoxide, pyrrolidine, N,N-dimethylformamide and ethyl cyanoacetate afforded 7-methoxy- 10 , 7-(1-pyrrolidyl)- 11 and 7-dimethylaminofuro[3,2-b]pyridine ( 14 ) and 7-(1-cyano-1-ethoxy-carbonyl)methylene-4,7-dihydrofuro[3,2-b]pyridine ( 12 ). Nitration of 2 with a mixture of fuming nitric acid and sulfuric acid gave 2-nitrofuro[3,2-b]pyridine N-oxide ( 15 ).     

Chemistry of sulfonyl isocyanates and sulfonyl isothiocyanates. IX. Routes to substituted oxazolidin-2-ones and oxazolidine-2-thiones

4-Chlorobenzenesulfonyl isocyanate (I) reacted with 2-chloroethanol and 1-chloro-2-propanol to give, respectively, 2-chloroethyl 4-chlorobenzenesulfonyl carbamate (III) and 1-chloro-2-propyl 4-chlorobenzenesulfonyl carbamate (VI). The carbamates III and VI cyclized under the influence of pyridine to afford, respectively, 3-(4-chlorobenzenesulfonyl)oxazolidin-2-one (IV) and 3-(4-chlorobenzenesulfonyl)-5-methyloxazolidin-2-one (VII). The oxazolidin-2-ones were stable toward hydrochloric acid but hydrolyzed in 2M sodium hydroxide solution to N-(2-hydroxyethyl)-4-chlorobenzenesulfonamide (V) and N-(2-hydroxy-1-propyl)-4-chlorobenzene-sulfonamide (VIII), respectively. 4-Toluenesulfonyl isothiocyanate (II) reacted with 2-chloroethanol to give 2-chloroethyl 4-chlorobenzenesulfonyl thiocarbamate (IX), which was converted by pyridine to 3-(4-toluenesulfonyl)oxazolidine-2-thione (X).     

Regioselectivity in lateral deprotonation of an isoxazolecarboxamide of (S)-prolinol. Conformational correlation by crystal structure solid state solution 13C NMR

The conformation at the amide functional group in 3,5-dimethylisoxazole-4-(S-2′-hydroxymethyl-N-pyrrolidino) carboxamide (1) has been determined by a single crystal X-ray determination. The ¹³C nmr in both deuteriochloroform solution and solid state show close agreement. The metalation behaviour of the amide is dependent upon the substitution on the 2′-hydroxymethyl moiety. Dianion studies indicate C-5 lateral metalation under both thermodynamic and kinetic conditions. Protection of this substituent as the methyl ether, 2 , gives rise to predominant C-3 lateral metalation under kinetic conditions and C-5 lateral metalation on equilibration. These observations can be explained using the Ireland-Evans model for chelation directed deprotonation.     

1,3-Dipolar cycloaddition reaction of aryl nitrile oxides with alkenes using imidazole and pyridine containing reusable polymeric base catalysts

Cross-linked poly-1-(4-vinylbenzyl)imidazole and cross-linked poly-4-vinylpyridine have been prepared from respective vinyl monomers using different quantities of divinylbenzene as a cross-linker by radical polymerization. The polymeric bases were characterized by FT-IR, TGA, field emission-scanning electron microscopy (FE-SEM), and Brunauer-Emmett-Teller (BET) surface area analysis. Their swelling behavior was also studied. They were used as base catalysts for 1,3-dipolar cycloaddition reaction of aryl nitrile oxides, generated in situ from N-hydroxyimidoyl chloride, with N-phenylmaleimide and ethyl acrylate, to obtain 3-arylisoxazolines. Both the bases gave excellent results. These polymers were reusable, safe to use, and provided good alternative for organic nonreusable bases like pyridine and triethylamine which are hazardous.     

Synthesis and anticonvulsant activity of 3-[3-[(dimethylamino)-methyl]-5-methyl-4H-1,2,4-triazol-4-yl]-4-(o-chlorobenzoyl)pyridine

Wolff-Kishner reduction of 3-amino-4-(o-chlorobenzoyl)pyridine ( 3 ) afforded 3-amino-4-(o-chlorobenzyl)pyridine ( 5 ), which on subsequent reaction with triethyl orthoformate and then acetyl hydrazide yielded 1-acetyl-2-[N-[4-(o-chlorobenzyl)pyridin-3-yl]formimidoyl]hydrazone ( 7 ). Cyclization of hydrazone 7 gave 3-(3-methyl-4H-1,2,4-triazol-4-yl)-4-(o-chlorobenzyl)pyridine ( 8 ), which on Jones oxidation yielded 3-(3-methyl-4H-1,2,4-triazol-4-yl)-4-(o-chlorobenzyl)pyridine ( 9 ). The Mannick reaction of 3-(3-methyl-4H-l,2,4-triazol-4-yl)-4-(o-chlorobenzyl)pyridine ( 9 ) with aqueous formalin and dimethylamine hydrochloride afforded 3-[3-[(dimethylamino)methyl]-5-methyl-4H-1,2,4-triazol-4-yl]-4-(o-chlorobenzoyl)-pyridine ( 10 ). 3-[3-[(Dimethylamino)methyl]-5-methyl-4H-1,2,4-triazol-4-yl]-4-(o-chlorobenzoyl)pyridine ( 10 ) exhibited good anticonvulsant activity in the subcutaneous pentylenetetrazole anticonvulsant screen indi cating that an appropriately substituted-pyridine ring moiety can serve as a bioisostere of a chlorobenzene ring with respect to anticonvulsant activity.     

Acetylenchemie. 9. Mitt. Anellierte imidazole aus N-propinylamid-vorstufen

The Compound 2-(N-Formyl-N-prop-2′-inyl)aminopyridine was cyclised in boiling formic acid to 3-methylimidazo[1,2-a]pyridine, with 3-methylene-2H-imidazo[1,2-a]pyridine as the intermediate. Under similar conditions the 1,3-diprop-2-inylpyrimido[4,5-b]quinoline-2,4-dione resulted from 1-methylimidazo[1,2-a]quinoline-4-carbonic acid-N-2-prop-2′-inylamide and from the 1-prop-2′-inylbenzo[b][1,8]naphthyridin-2-one the 1-methylbenzo[b]imidazo[1,2,3-ij]naphthyridine-4,7-dione as a new ring system, was obtained.     

Chemistry of thienopyridines. VIII. Substitution products derived from thieno[2,3-b] pyridine 7-oxide

Thieno[2,3-b]pyridine (I) was concerted to the N-oxide (II, 53%) by means of hydrogen peroxide and acetic acid. Nitration of II in sulfuric acid gave 4-nitrothieno[2,3-b]pyridine 7-oxide (III, 50%), while nitration in acetic acid formed the isomeric 5-nitrothieno[2,3-b]pyridine 7-oxide (IV, 54%). Compounds III and IV were reduced to the corresponding 4- and 5-aminothieno[2,3-b]pyridines, respectively. Treatment of III with acetyl chloride gave 4-chlorothieno-[2,3-b]pyridine 7-oxide (XI, 81%), convertible in two steps to 4-(N-substituted amino)thieno-[2,3-b]pyridines (especially of the 4-dialkylaminoalkylamino type) for screening as potential antimalarial drugs. 4-Aminothieno[2,3-b]pyridine reacted with aromatic aldehydes to give Schiff's bases and other products. Mechanisms for some of the reactions are suggested. NMR spectral data are reported for various 4-substituted thieno[2,3-b]pyridine compounds.     

g-C3N4/双钙钛矿复合材料的制备及氧催化性能

通过溶胶-凝胶法制备出不同Ni掺杂比例的双钙钛矿Sr_2Ni_xCo_(2-x)O_6(x=0.2,0.4,0.6,0.8),通过热分解法制备出具有层状结构的纳米颗粒g-C_3N_4,并制备其复合物催化剂。将双钙钛矿和g-C_3N_4分别制备成双功能电极片,用于测试其对氧还原(ORR)和氧析出(OER)的催化活性,然后选取具有最佳氧催化活性的Ni掺杂比例x=0.4的双钙钛矿与一定重量比例的g-C_3N_4进行复合,测试复合催化剂的氧催化活性。结果表明,复合后的催化剂催化效果明显优于单一催化剂,当g-C_3N_4添加量占双钙钛矿的30%(w/w)时复合催化剂催化氧还原反应的最大电流密度为395.7 mA·cm~(-2)(-0.6 V vs Hg/HgO),氧析出反应的最大电流密度为372.0mA·cm~(-2)(1 V vs Hg/HgO),这表明g-C_3N_4与Sr_2Ni_(0.4)Co_(1.6)O_6复合后协同催化能够提高双钙钛矿的氧催化活性。     

Synthesis of N,N'-Diacyl-1,2-di-(4-pyridyl)ethylenedianiines

Reaction of N-(4-pyridylmethyl)benzamide N-oxides with acetic anhydride yielded dimerization compounds. This dimerization occurs at the atom attached to the pyridine ring. These compounds so obtained were evaluated for analgesic and antiinflammatory activity.     

Multifunctional hydrolytic catalyses. IX. Hydrolysis of p-nitrophenyl acetate by bifunctional polymer catalysts containing zwitterionic (hydroxamate) nucleophiles

The hydrolysis of p-nitrophenyl acetate by bifunctional polymer catalysts was studied in 28.9% EtOH–H₂0 at 30°C. Partial (ca. 10 mole%) quaternization of poly(4-vinylpyridine) and poly(1-vinyl-2-ethylimidazole) with benzyl N-benzyl chloroacetohydroxamate and the subsequent removal of the benzyl group produced water-soluble polymers containing zwitterionic hydroxamate groups and free pyridine (or imidazole) groups. The zwitterionic hydroxamate was a nucleophile more than 10 times as effective as simple hydroxamate anions, and the acetyl hydroxamate intermediate was efficiently hydrolyzed by the intrapolymeric pyridine (or imidazole) group. Thus, the catalytic efficiency of these bifunctional polymers was much better than monofunctional polymers which contain either hydroxamate or imidazole, and amounted to 10–20% of that of α-chymotrypsin under a comparable condition.     

4-Dialkylaminopyridines as Highly Active Acylation Catalysts. [New synthetic method (25)]

The synthesis of 4-dialkylaminopyridines can be accomplished in two steps starting from pyridine. Compared to pyridine, these derivatives are approximately 10⁴ times more active when used as acylation catalysts. Dialkylaminopyridines are being used with ever-increasing frequency for acylation reactions which proceed either incompletely or not at all in pyridine. This article reviews the various possible applications of 4-dialkylaminopyridines in terpene, steroid, carbohydrate and nucleoside chemistry as well as in the transformation of amino acids into α-acyl aminoketones and polymerization of isocyanates. In addition, N-substituted 4-dialkylaminopyridinium salts can be used for the transfer of sensitive groups to nucleophiles in aqueous medium. The exceptional catalytic effect of these derivatives, even in non-polar solvents, is due, in part, to the formation of high concentrations of N-acylpyridinium salts which are present in solution as loosely-bound, highly reactive ion pairs.     

Synthesis of some benzimidazole-, pyridine- and imidazole-derived chelating agents

Procedures are described for the preparation of various bidentate and potentially tridentate chelating agents. These incorporate pyridyl, benzimidazole, imidazole or phenolic moieties. Phillips condensations of carboxylic acids with o-phenylenediamines were carried out in 4 M hydrochloric acid. Syntheses are reported for 2, 6-bis(N′-methylimidazol-2′-ylthiomethyl)pyridine, 2, 6-bis(benzimidazol-2′-ylthiomethyl)pyridine, 2-(4′-piperidyl)benzimidazole, 2-(3′-piperidyl)benzimidazole, 2-(3-N′-methylpiperidyl)benziinidazole, 2-(3-N′-methylpiperidyl)-N-methylbenzimidazole, 2-(2′-hydroxybenzyl)benzimidazole and 2-(2′-hydroxyben-zyl)N-methylbenzimidazole. The compounds were characterized where appropriate by their mass, uv, and ¹H-nmr spectra. 2-(2′-Hydroxybenzyl)benzimidazole hydrochloride acts as a gelling agent in aqueous solution.     

Fused s-triazino heterocycles. XVI. 13H-1,3,7,8,12a, 13c-hexaazabenzo[de]naphthacene and 1,3,7,8,11b, 12,14,14d-octaazadibenzo[de,hi]naphthacene,two new ring systems

The reaction of 7,9-dibromo-5-tribromomethyl-2-t-butyl-4-cyano-1,3,6,9b-tetraazaphenalene ( 1a ) with 2-amino-5-picoline is shown to give 4,6-dibromo-2-t-butyl-13-imino-11-methyl-13H-1,3,7,8,12a,13c-hexaazabenzo[de]naphthacene ( 3 ) and the isomeric 7,9-dibromo-2-t-butyl-4-cyano-5N-(5-methyl-2-pyridyl)amino-1,3,-6,9b-tetraazaphenalene ( 2a ). A related annulation reaction of 7,9-dibromo-2-t-butyl-5-chloro-4-cyano-1,3,6,9b-tetraazaphenalene ( 1g ) with 2-amino-6-trimethylacetamidopyridine leads in two steps to 4,6-dibromo-2,13-di-t-butyl-1,3,7,8,11b,12,14,14d-octaazadibenzo[de,hi]naphthacene ( 4a ). The preparation of 1g , 5-azido-7,9-dibromo-2-t-butyl-4-cyano-1,3,6,9b-tetraazaphenalene ( 1c ) and the reaction of the latter with pyrrolidine leading to 7,9-dibromo-2-t-butyl-4-cyano-5-(1-pyrrolidino)-1,3,6,9b-tetraazaphenalene ( 1e ) are also reported. Attempted displacement of the azido-group on 1c by 2,6-diaminopyridine affords surprisingly 5-amino-7,9-dibromo-2-t-butyl-4-cyano-1,3,6,9b-tetraazaphenalene ( 1d ).     

Substituted pyridine coordinated N,N-trans and N,N-cis cyclopalladated complexes of (S)-4-tert-butyl-2-phenyl-2-oxazoline: Crystal structures, spectral study and catalysis of the decomposition of PS pesticides

Three pyridine coordinated cyclopalladated complexes: (S)-chloro{2-[2-(4-tert-butyl)oxazolinyl]phenyl-C,N}(4-R-pyridine)palladium(II) (R = H, 2; R = CF₃, 3; R = NMe₂, 4), have been synthesized and structurally characterized. While the crystal structure shows that 2 has a normal N,N-trans-conformation in the coordination sphere of palladium(II), 3 and 4 exhibit uncommon N,N-cis-conformations. From ¹H NMR measurements, the major coordination isomer in deuterated chloroform solution is N,N-trans configuration for three palladacycles. It was found that the three complexes catalyze effectively the methanolysis of the PS pesticides including chiral thiophosphates but show different activity depending on the substituents of co-coordinated pyridine ring in 2–4.     

Synthesis and reactions of 3-acetyl-6-methyl-2-(methylthio)pyridine

A reaction of methyllithium with 3-cyano-6-methylpyridine-2(1 H)-thione followed by alkylation of the resulting 3-acetylpyridinethione, or a direct reaction of methyllithium with 3-cyano-6-methyl-2-(methylthio)pyridine, afforded 3-acetyl-6-methyl-2-(methylthio)pyridine. The ketone obtained was examined in bromination reactions under various conditions. Bromi-nation in methanol or chloroform, proceeding through the formation of sulfonium bromides, gave substituted 3-(bromoacetyl)pyridine. A reaction of 3-acetyl-6-methyl-2-(methyl-thio)pyridine with N-bromosuccinimide in CCl4 afforded N-(pyridinesulfenyl)succinimide. The bromo ketone was used for the synthesis of various heterocyclic compounds.     

Triaziridine 8. Mitteilung. Zur Acylierung Von Dialkyl-triaziridinen

On the Acylation of Dialkyl-triaziridines (2,3-trans)-Diisopropyl- ( 1 ) and (2,3-cis)-1,3-cyclopentylenetriaziridine ( 2 ) were reacted with ClCOOCH₃. In the case of 1 , with or without pyridine, an expected acylation at N(1) resulted in the methoxycarbonyl derivative 3 . In the case of 2 , the reaction in pyridine led to the γ- and α-dihydropyridyl derivatives 5 and 6 , respectively, where the acylpyridinium moiety had become attached by a ring C-atom to N(1); without pyridine, it afforded the N-cyclopentenylcarbamates 13 and 14 by opening of the triaziridine ring and loss of N₂. The mechanisms proposed for these reactions involve the initial attack of an electrophile at N(1) of 1 but at N(2) (or N(3)) of 2 . This difference is rationalized with steric factors, inasmuch as the hindrance to an attack at N(2) (or (3)) is greater in i than in 2 , whereas this hindrance at N(1) is smaller in 1 than in 2 . The greater resistance to opening of the saturated N₃-homocycle during acylation of the monocyclic triaziridine 1 , as compared to that of the tricyclic one 2 , is attributed to greater strain in the latter system.     

Pyridine N-sulfides. Benzisothiazolo[2,3-a]pyridinium tetrafluoroborates and benzothiopheno[3,2-b]pyridines. Novel heterocyclic systems

2-(2-Mercaptophenyl)pyridines are prepared from the corresponding phenols and oxidized with N-chloro-succinimide and silver tetrafluoroborate to benzisothiazolo[2,3-a]pyridine salts ( 4 ). The latter do not rearrange thermally or photochemically to benzothiopheno[3,2-b)pyridines ( 19 ) and are attacked by nucleophiles at sulfur rather than in the pyridine ring, to give the original 2-(2-mercaptophenyl)pyridine back in a reaction involving a dismutation. 19 is prepared by rearranging O-[2-(3-bromo-2-pyridyl)-4-nitrophenyl]dimethylthio-carbamate to the S-aryl compound and heating the latter with strong base.     

Heterocyclic synthesis with N-oxides. Preparation of pyridine n-oxide substituted chromones,chromanones, coumarins,quinolones, dihydroquinolones and cinnolones

The synthesis of pyridine N-oxide substituted chromones, chromanones, coumarins, quinolines, dihydroquinolines and cinnolines from l-(2-hydroxyphenyl)-2-(2-pyridinyl)ethanone N-oxide, 1-(2-aminophenyl)-2-(2-pyridinyl)ethanone N-oxide and 1-[2-(methylamino)phenyl]-2-(2-pyri-dinyl)ethanone N-oxide is described.     

Equilibrium of Acetyl Transfer between Pyridine N-Oxides and Their Acetylonium Salts

The equilibrium constants of acetyl transfer between O-acetylonium salts of a series of pyridine N-oxides and 4-(4-dimethylaminostyryl)pyridine N-oxide in acetonitrile and methylene chloride were determined. The equilibrium constants correlate with the acid-base characteristics of the N-oxides and with the heats of reactions calculated quantum-chemically.