Catalytic hydroformamination of 2,5-dimethoxy-2,5-dihydrofurans

N-Substituted 3- and 4-formylpyrroles have been obtained by hydroformamination of 2,5-dimethoxy-2,5-dihydrofurans in the presence of HRh(CO)(PPh₃)₃.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1837–1840, August, 1990.     

Hetarylethylene derivatives of 2,5-diphenyloxazole

A number of new effective luminophores were synthesized by PO olefination from 2-(4-bromomethylphenyl)-5-phenyloxazole and various heterocyclic aldehydes containing a furan ring. All of the compounds obtained have intense fluorescence in toluene and, depending on the nature of the substituents, the color of the luminescence changes from blue to green. It is shown that chloro, bromo, and methyl substituents have little effect on the spectral-luminescence properties of the compounds obtained, whereas a nitro group causes a decrease in the fluorescence quantum yield.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1616–1618, December, 1977.     

Synthesis of selenophene-2,5-dicarboxylic acid

Selenophene-2,5-dicarboxylic acid was obtained by liquid-phase oxidation of 2,5-dimethylselenophene with molecular oxygen.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, p. 1605, December, 1972.     

Synthesis of 2,5-diisoxazolyltetrahydrofurans

The synthesis of 2,5-bis(3-bromo-5-isoxazolyl)tetrahydrofuran ( 2 ) and 2,5-bis(3-methoxy-5-isoxazolyl)tetrahydrofuran ( 3 ) have been accomplished in three and four steps respectively. Cis- and trans-isomers have been separated and fully characterized. Differently from synthetic schemes so far utilized for the preparation of the 2,5-diheteroaryltetrahydrofuran analogs, our approach involves the direct synthesis of a key intermediate containing both isoxazole rings and diol function for the final cyclization. Starting from succinic aldehyde, the new 1,7-octadiyne-3,6-diol ( 4 ) was prepared and was submitted to a double cycloaddition with bromonitrile oxide to yield the key intermediate 1,4-bis(3-bromo-5-isoxazolyl)-1,4-butanediol. The methoxy analogs 3 were obtained by methanolysis of the bromo derivatives 2 .     

2,5-二取代-1,3,4-三唑的合成

以苯甲酰氯、硫氰酸钾和芳胺为起始原料, 合成了1-苯甲酰基-3-芳基硫脲1a～1g, 再与水合肼反应合成了2,5-二取代-1,3,4-三唑2a～2g. 化合物2的结构经IR, ¹H NMR和HRMS确证.     

Biologically Active 1-Aminodeoxy and 1-O-Alkyl Derivatives of The Powerful D-Glucosidase Inhibitor 2,5-Dideoxy-2,5-Imino-D-Mannitol

ABSTRACT

By an Amadori rearrangement of easily available 5-azido-5-deoxy-D-glucofuranose with dibenzylamine and subsequent catalytic hydrogenation of the resulting 5-azido-1-(N,N-dibenzyl)amino-1,5-dideoxy-D-fructopyranose, 1-amino-1,2,5-trideoxy-2,5-imino-D-mannitol was obtained in only two steps and in excellent overall yield. Likewise, other amines were employed to introduce extended side chains ultimately suitable for attachment of the inhibitor to solid supports. The reported rearrangement reaction is a high yielding, convenient and apparently general entry to 1-aminodeoxyketopyranoses modified at C-5, facilitated by the ring enlargement of the aldofuranose to the ketopyranose as an additional driving force. A range of selected chain extended analogues was prepared by acylation of N-1. Inhibitors obtained exhibit K _i-values with D-glucosidases in the micromolar range. Interestingly, 1-N-acylation resulted in superior inhibitory activities, as did the addition of a hexyl chain.     

2,5,-Dimethoxy- and 2,5-di-n-butoxy-1,4-benzoquinone reactions and polymerization with 1,6-hexanediamine

The serendipitous formation of 2,5-dimethoxy- 1,4-benzoquinone is reported from the reaction of 1,4-benzoquinone with methanol, DABCO, and paraformaldehyde. This monomer, and its di-n-butoxy analog, are also available from 2,5-dihydroxy-1,4-benzoquinone. These materials are capable of novel polycondensation reactions with diamines such as 1,6-hex-anediamine. Use of m-crexsol as polymerization solvent gave a dark, insoluble product while various amide solvents lead to orange or pink polymers that had average degrees of polymerization from 5 up to >30. These polymers, Plus model compounds obtained from 1-aminopropane and N,N'- dimethyl-1,6-hexanediamine, were characterized by FTIR, solution, and solid-state NMR.     

Asymmetric homogeneous hydrogenation of 2,5-disubstituted furans

A homogeneous catalyst system for the asymmetric cis-hydrogenation of 2,5-disubstituted furans leading to 2',3'-dideoxynucleoside analogues is described. Best enantioselectivities (ee values of up to 72%) were obtained with cationic rhodium complexes ligated by diphospholanes of the butiphane family. The selectivity of the hydrogenation was reversed by the addition of a base or a polar protic solvent in certain cases. Ferrocene- and proline-based systems gave significant, but lower, ee values.     

Salts of 2,5-dimercapto-1,3,4-thiadiazole

Reaction of 2,5-dimercapto-1,3,4-thiadiazole with ammonia or pyridine gives monoammonium or monopyridinium slats, and the reaction with hydrazine hydrate gives both mono- and dihydrazine salts, which was confirmed by alkylation of the salts obtained. Difference in the chemical shifts of the SCH₂R groups was found in the¹H NMR spectra of the mono- and dialkyl-substituted 2,5-dimercapto-1,3,4-thiadiazoles.Institute of Chemistry, Vilnius LT-2600, LithuaniaTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 682–687, May, 2000.     

Thermochemistry of 2,5-thiophenedicarboxylic acid

The enthalpies of combustion and sublimation of 2,5-thiophenedicarboxylic acid [CASRN 4282-31-9] were measured by rotary-bomb combustion calorimetry and the method of transference in a saturated stream of nitrogen, and the gas-phase enthalpy of formation was determined, Delta(f)H(o)(m)(g) = -(632.6 +/- 2.2) kJ x mol(-1). Standard ab initio molecular orbital calculations at the G2(MP2) and G3(MP2) levels were performed, and a theoretical study on the molecular and electronic structure of the compound has been carried out. The three most stable conformers have been explicitly taken into account. The calculated enthalpy of formation averaged using three different isodesmic reactions, -631.1 kJ x mol(-1), is in very good agreement with the experimental value. A comparison of the substituent effect of the carboxylic groups in benzene and thiophene ring has been made. The relative stability obtained for the substitution of two H atoms by COOH in position 2,5- for thiophene and 1,4- for benzene involve the same energetic effects, DeltaDelta(f)H(o)(m)= -747.6 +/- 2.4 and -748.2 +/- 2.7 kJ x mol(-1), respectively.     

对苯醌-2,5-二羧酸酯的合成

氢醌-2,5-二羧酸酯(2a,b)用活性MnO~2氧化高产率地得到对苯醌-2,5-二羧酸酯(3a,b). 氢醌-2,5-二羧酸乙酯(2b)也能用PhI(O~2CCF~3)~2氧化成相应的对苯醌(3b). 在这个反应中,3b可以被环戊二烯捕获,并进一步与CF~3CO~2H反应. 当用2molPhI(O~2CCF~3)~2时, 得到3,6-二-三氟乙酰氧基氢醌-2,5-二羧酸乙酯(6),而在吡啶存在下, 得到6-吡啶基氢醌-2,5-二羧酸乙酯三氟乙酸盐.     

丙炔醇环四聚体的辐射化学研究

用γ-射线对丙炔醇环四聚体的晶体进行照射,无色透明的晶体逐渐变为棕色;利用红外光λ和核磁共振等方法研究了晶体的变化;ESR证实辐照产生了大量的自由基,测得自由基的g值是2.0048,自旋浓度为10~(17)～10~(17)spins/g;对晶体进行加热处理表明该自由基在低于110℃时相当稳定,很少复合,但可发生自由基反应而生成更稳定的自由基;探讨了自由基的碎裂、复合生成聚合产物以及通过链反应生成高聚物的机理。     

Facile synthesis of macrocyclic tetrazoles by regioselective cycloalkylation of bistetrazoles with 2,5-dimethylhexane-2,5-diol in perchloric acid

Alkylation of 1,5-bis(tetrazol-5-yl)-3-oxapentane with 2,5-dimethylhexane-2,5-diol in 65% aqueous perchloric acid was found to proceed selectively on the N2 atoms of both tetrazole rings generating a 15-membered macrocycle with tetrazol-2,5-diyl moieties incorporated (yield ca. 80%). Under analogous alkylation conditions 1,5-bis(1-methyltetrazol-5-yl)-3-oxapentane undergoes quaternization resulting in a macrocyclic tetrazolium perchlorate containing two 1-methyltetrazolium-3,5-diyl units linked by 3-oxapentane-1,5-diyl and 2,5-dimethylhexane-2,5-diyl bridges. Crystal structures of the macrocyclic compounds obtained, determined by single crystal X-ray analysis, are described.     

Cyclobutane-substituted diacetamido sulfides and 2,5-diacylthiophenes

A general and convenient route for the synthesis of 2,5-di[1-methyl-1-arylcyclobutane-3-yl]- thiophenes 4a–c and bis[1-methyl-1-arylcyclobutane-3-yl]-2-(2-oxyethtylamido)thiazole sulfides 7a–c is reported. The characterization of these compounds was obtained by elemental analyses, IR, ¹³C, and ¹H NMR techniques. © 2003 Wiley Periodicals, Inc. 15:26–31, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.hc10207     

Polymers derived from 2,5-diamino-p-benzoquinone-diimide and related compounds

A number of new polymeric materials have been prepared by the self-condensation of 2,5-diamino-p-benzoquinonediimide and by its condensation with 2,5-diamino-p-benzoquinone, 2,5-dihydroxy-p-benzoquinone, and 2,5-dichloro-p-benzoquinone. Ladder polymers were expected, but in every case polymers with some open rings were obtained. 2,5-Diaminohydroquinone was condensed with 2,5-diamino-p-benzoquinonediimide and with 2,5-diamino-p-benzoquinone to produce heat stable polymers but the expected ladder structures were not obtained. Thermogravimetric analyses of the polymers in nitrogen all showed a weight loss at 100–150°C of 3–14% which was presumably due to loss of either chemically combined or absorbed water on the polymer and then only a 5% weight loss up to about 600°C with a final weight loss of 19% at 900°C.     

Facile synthesis of 2,5-diacylthiophenes

A base-catalyzed condensation of diketo sulfides [(RCOCH₂)₂S] with glyoxal affording 2,5-diacylthiophenes has been effected under mild conditions. Excellent results were readily obtained when R was various substituted phenyl, thienyl, or t-butyl groups. Although the yield for R = methyl was poor, the increase in length of the aliphatic chain markedly increased the yields.     

Synthesis and Reactions of Novel 2,5-Disubstituted 1,3,4-Thiadiazoles

The desired 1,3,4-thiadiazole compounds bearing different substituents were obtained by the cyclization of the corresponding thiosemicarbazide followed by the reaction with electrophilic reagents, such as aromatic aldehydes, isatin, phenyl isothiocyanate, and carbon disulfide. The newly synthesized 2,5-disubstituted 1,3,4-thiadiazoles were obtained in good yields and their structures were elucidated by spectral data and elemental analysis.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Synthesis of 2,5-dihydroxy-3-(indol-3-yl)benzoquinones by acid-catalyzed condensation of indoles with 2,5-dichlorobenzoquinone

Three methods for the conjugate addition of indoles to 2,5-dichlorobenzoquinone have been developed. A wide variety of indoles substituted with halogen, alkyl, alkoxy, and aryl groups participate in anaerobic condensation reactions promoted by HCl, H2SO4, or CH3CO2H. The hydroquinone product is partially oxidized by excess dichlorobenzoquinone and fully converted to the 2,5-dichloro-3-(indol-3-yl)benzoquinone targets by DDQ or Ag2CO3 oxidation. 2,5-Dihydroxy-3-(indol-3-yl)benzoquinones can be obtained from the dichlorides by alkaline hydrolysis. The rotational characteristics of the biaryl bond created in these reactions have been examined by theoretical and spectroscopic methods.     

反式-2,5-二芳基四氢呋喃合成的新方法

以(±)4,10-二氧杂三环[5,2,1,0_2,6]-癸-8-烯-3-醇为原料,经过芳基化、氧化、芳基化、环化、热分解和加氢反应,得到PAF新的拮抗物反式-2,5-二芳基四氢呋喃,并合成了化合物8.     

Synthesis of fluorine-containing esters of 2,5-furandicarboxylic acid

Fluorinated esters of 2,5-furandicarboxylic acid have been synthesized starting from 2,5-furan dicarboxylic acid dichloride and fluorine-containing diols. The reaction control was performed by means of ¹H, ¹⁹F NMR, and IR-spectroscopy. Thermal stability, as well as glass transition temperature, and intrinsic viscosity parameters of the obtained oligomers have been determined.