The Reaction of 2,5-Dimethoxy-2,5-Dihydrofuran with Dichloroketene

2,5-Dimethoxy-2,5-dihydrofuran (DDF) reacts with dichloroketene to give 7,9-dimethoxy-3,3,5,5-tetrachloro-8-oxabicyclo[4,3,0]-noan-2,4-dione (I), and methyl chloro-(2,5-dihydro-5-methoxy-2-furanylidene) acetate (II). The reactions of 2,5-dihydrofuran and 2,5-dimethoxy-tetrahydrofuran with dichloroketene were also-studied for comparison. Compound II was derived from the insertion of a molecule of dichloroketene into the C-O bond of DDF with subsequent dehydrochlorination. Compound I resulted from the cycloaddition of two molecules of dichloroketene to the C=C bond of DDF. A mechanism involving a 1,5-dipolar intermediate is proposed to account for this novel reaction.     

Syntheses and properties of donor-acceptor-type 2,5-diarylthiophene and 2,5-diarylthiazole

[structure: see text] Syntheses of differently substituted 2,5-diarylthiophenes and 2,5-diarylthiazoles are carried out with the palladium-catalyzed C-H substitution reaction using AgF as an activator. Remarkably strong photoluminescence is observed in 2,5-diarylthiophene. Differences between the physical properties of liquid crystalline characteristics and cyclic voltammograms of thiophene and thiazole are also studied.     

Synthesis and characterization of polymers derived from 2,5-dimethoxy-terephthaldehyde and 2,5-dimethoxy-terephthalic acid

Polyamides were synthesized from 2,5-dimethoxyterephthaloyl dichloride and diamines. Also, polyimines and polyaldoles were prepared from 2,5-dimethoxy-terephthaldehyde with diamines and ketones. The polymers were characterized by elemental analysis and infrared and NMR spectroscopy. Their intrinsic viscosity, glass transition temperature, and thermaldecomposition temperatures were determined.     

Mechanism and selectivity of radical alkylation of 3,4-Dichloro-2,5-dihydrofuran-2,5-dione

The mechanism of radical alkylation of 3,4-dichloro-2,5-dihydrofuran-2,5-dione with cyclohexane and 2,3-dimethylbutane follows an addition-elimination pattern with reversible formation of alkyl radicals. The proposed kinetic scheme takes into account the possibility for isomerization of primary 2,3-dimethylbutane radicals into tertiary and is consistent with the experimental data. The regioselectivity of the process is linearly related to the concentration of hydrogen chloride, so that the rate constant for the addition of primary 2,3-dimethylbutane radical to 3,4-dichloro-2,5-dihydrofuran-2,5-dione may be estimated. Effective procedures for the synthesis of 3-chloro-4-(2,3-dimethylbut-2-yl)-, 3-chloro-4-cyclohexyl-, and 3,4-dicyclohexyl-2,5-dihydrofuran-2,5-diones have been proposed.     

Synthesis and Chemistry of 2,5-Dimethylene-2,5-Dihydrofuran

2,5-Dimethylene-2,5-dihydrofuran (3), generated flash pyrolitically, underwent di- and trimerization reactions to give cyclic dimer and trimer. Compound 3 was trapped with methanol, ethanol, bromine, acetic acid, thiophenol and oxygen. Results from trapping experiments suggest that the diradical form of 3 is involved.     

Absolute configuration and conformational stability of (+)-2,5-dimethylthiolane and (-)-2,5-dimethylsulfolane

Enantiopure (+)-2,5-dimethylthiolane and (-)-2,5-dimethylsulfolane were prepared using literature procedures and investigated using vibrational circular dichroism (VCD). Experimental absorption and VCD spectra of (+)-2,5-dimethylthiolane and (-)-2,5-dimethylsulfolane in CCl(4) solution in the 2000-900 cm(-)(1) region were compared with the ab initio predictions of absorption and VCD spectra obtained with density functional theory using the B3LYP/6-311G(2d, 2p) basis set for different conformers of (2R,5R)-2,5-dimethylthiolane and (2R,5R)-2,5-dimethylsulfolane. This comparison indicates that (+)-2,5-dimethylthiolane is of the (2R,5R)-configuration and has two predominant conformations in CCl(4) solution. In addition, (-)-2,5-dimethylsulfolane is of (2R,5R)-configuration and has only one predominant conformation. The stereochemical assignment is in agreement with literature.     

Use of palladium-mediated allylic substitution reactions in the synthesis of 2,5-disubstituted-2,5-dihydrofurans

2,5-Disubstituted-2,5-dihydrofurans were synthesised in both one- and two-pot reactions starting from 2,5-diacetoxy-2,5-dihydrofuran. These palladium-mediated allylic substitution reactions were useful in preparing symmetrical or unsymmetrical products by employing the same nucleophile twice or two different nucleophiles, respectively.     

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.     

The synthesis and photolarvicidal activity of 2,5-diarylethynylthiophenes

The photoactivatable insecticides have photoactive features and broad applications. The derivatives of the alpha-terthienyl analogues were synthesized for evaluating their photolarvicidal activities and 13 2,5-diarylethynylthiophenes were investigated to determine their effect on the second-instar larvae of Plutella xylostella L. Based on their photolarvicidal activities, the 2,5-Dithienylethynylthiophene, 2,5-Diphenylethynylthiophene, 2,5-Di-4-Methoxylphenylethynylthiophene and 2,5-Di-3,4-Methylenedioxyphenylethynylthiophene were found to be the most potent compounds, and their LC(50) values were 34.1 mg l(-1), 48.4 mg l(-1), 60.8 mg l(-1) and 42.7 mg l(-1), respectively. The relationship analysis between structure and activity showed that the middle thiophene ring played an important role on the activities. The electron donor substituents increased the photolarvicidal activities and the length of the alkyl chain had negative influence on the activities.     

Structural diversity in the first metal complexes of 2,5-dicarboxamidopyrroles and 2,5-dicarbothioamidopyrroles

Metal complexes of 2,5-dicarboxamidopyrroles and 2,5-dicarbothioamidopyrroles have been structurally characterised for the first time, complementing the significant amount of work that has been reported for the analogous pyridine ligands. N,N'-Bis(3,5-dinitrophenyl)-3,4-diphenyl-1H-pyrrole-2,5-dicarboxamide forms octahedral bis(tridentate) complexes with cobalt(iii) and nickel(ii), where the ligands are bound to the metal centres through deprotonated pyrrole and amide N atoms. N,N'-Dibutyl-3,4-diphenyl-1H-pyrrole-2,5-dicarboxthioamide and N,N'-diphenyl-3,4-diphenyl-1H-pyrrole-2,5-dicarboxthioamide also form bis(tridentate) cobalt complexes but are only deprotonated at the pyrrole N atom, the remainder of the coordination sphere comprising the thioamide S atoms. The dibutyl derivative was isolated as a Co(ii) complex, whereas the diphenyl system deposited a Co(iii) complex. In contrast, N,N'-dibutyl-3,4-dichloro-1H-pyrrole-2,5-dicarboxamide was found to act as a bidentate ligand, in an octahedral cobalt(ii) complex comprising of two bidentate pyrrole ligands, and two aqua ligands. Synthesis of N,N-bis(pyridin-2-ylmethyl)-3,4-diphenyl-1H-pyrrole-2,5-carboxamide gave a pyrrole ligand with increased denticity. Reaction with cobalt(ii) chloride resulted in the isolation of a dinuclear helicate complex. The ligand was found to have undergone addition of a methoxy group to one of the linking methylene carbons, presumably as a result of the oxidative addition of solvent methanol.     

Investigation of furan compounds L. Synthesis of N-alkyl- and N-aryl-substituted diureides of tetrahydrofuran-2,5- and tetrahydrothiophene-2,5-dicarboxylic acids

The corresponding diureides of tetrahydrofuran-2,5- and tetrahydrothiophene-2,5-dicarboxylic acids and the dithioureide of tetrahydrothiophene-2,5-dicarboxylic acid were obtained by the acylation of thiourea, urea, and its N-methyl-, N-tert-butyl- and N-phenyl derivatives with the acid dichlorides of tetrahydrofuran-2,5- and tetrahydrothiophene-2,5-dicarboxylic acids.See [1] for communication XLIX.DeceasedTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1587–1589, December, 1971.     

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.     

Synthesis and properties of polyurethanes and polyureas containing 2,5-thiophenylene linkage

A novel diisocyanate monomer, thiophene-2,5-diisocyanate (ThDI) was prepared from readily available adipic acid via the intermediate formation of thiophene-2,5-dicarboxylic acid chloride (ThDAC) and thiophene-2,5-dicarboxylic acid azide (ThDAA) which was subjected to a Curtius rearrangement. Polyurethanes and polyureas containing 2,5-thiophenylene linkage were synthesized by the polycondensation of thiophene-2,5-diisocyanate with various diols and diamines, respectively, in N,N-dimethylformamide. Polymerization conditions were optimized and the high yields of polymers were obtained. The identity of ThDI, model compounds, and the resulting polymers was confirmed by elemental analysis and spectroscopic methods. These polyurethanes and polyureas were found to have inherent viscosities in the range of 0.33–0.68 dL/g. Some physical properties of these polymers were also investigated.     

Synthesis and polymerization of 2,5-dimethylene-2,5-dihydrothieno[3,2-b]thiophene derivatives: The structure and reactivity of quinonoid monomers

Novel 2,5-dimethylene-2,5-dihydrothieno[3,2-b]thiophene derivatives such as 2,5-bis[di(ethylthio)methylene]-2,5-dihydrothieno[3,2-b]thiophene ( 4b ) and 2,5-bis[cyano(ethylthio)methylene]-2,5-dihydrothieno[3,2-b]thiophene ( 4c ) were successfully synthesized as isolable crystals. Polymerization behavior of 2,5-bis(dicyanomethylene)-2,5-dihydrothieno[3,2-b]thiophene ( 4a ), 4b , and 4c was investigated. 4a , 4b , and 4c are not homopolymerizable with any initiators and also not copolymerizable with vinyl monomers such as styrene (St), methyl methacrylate, and acryronitrile except for an alternating copolymerization of 4a with St. 4a , 4b , and 4c did not copolymerize with 7,8-bis(butoxycarbonyl)-7,8-dicyanoquinodimethane (BCQ) as a highly conjugated comonomer and instead only homopolymer of BCQ was obtained, indicating that they are much less reactive than BCQ. To obtain the relative reactivity among 1c , 2c , and 4c , the rate of addition reaction of 2,2′-azobis(isobutyronitrile) (AIBN) with 4c was compared with those of AIBN with 7,8-bis(ethylthio)-7,8-dicyanoquinodimethane ( 1c ) and with 2,5-bis[cyano(ethylthio)methylene]-2,5-dihydrothiophene ( 2c ) by NMR spectroscopy and analyzed with the first-order kinetics. The relative reactivity among 1c , 2c , and 4c was found to be as follows: 1c > 4c > 2c . The relationship between structure and reactivity for the quinonoid compounds was discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3027–3039, 1999     

Protolytic cleavage of derivatives of 2,5-dimethoxy-2,5-dihydrofuran

By analysis of the products from the protolytic cleavage of methyl 3-(2,5-dialkoxy-2,5-dihydro-2-furyl)propionate (I) in the presence of mixed nucleophiles and investigation of their mutual transformations the main paths in the dissociation of the protonated molecule of (I), with the formation of both linear cleavage products (derivatives of 1,4-diketones and 4-ketopimelic acid) and furylcarbinol derivatives, were determined.Latvian Institute of Organic Synthesis. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 190–197, February, 1997.     

Acid-mediated cycloalkylation of C-aminoazoles with 2,5-dimethylhexane-2,5-diol

Alkylation of 5-aminotetrazole with 2,5-dimethylhexane-2,5-diol in perchloric acid was found to proceed on an endocyclic nitrogen atom as well as on the amino group, giving 5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-4H-tetrazolo[1,5-a][1,3]diazepine. Under analogous conditions, 3-amino-1,2,4-triazole undergoes cycloalkylation of the neighboring N1 and N2 atoms of the heterocycle resulting in 1-amino-5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-[1,2,4]triazolo[1,2-a]pyridazinium perchlorate. The crystal structures of the products were determined by single crystal X-ray analysis.     

Synthesis and catalytic oxidation of 2,5-dimethylpyrazine

The classical method for obtaining 2,5-dimethylpyrazine by cyclization of amino-acetone has been improved by use of ammonium persulfate in place of mercuric chloride in the stage of catalytic oxidation of 2,5-dimethyldihydropyrazine. Catalytic vapor phase oxidation of 2,5-dimethylpyrazine gave 5-methylpyrazine-2-aldehyde and pyrazine-2,5-dialdehyde.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1124–1126, August, 1986.     

One-pot oxidation and bromination of 3,4-diaryl-2,5-dihydrothiophenes using Br2: synthesis and application of 3,4-diaryl-2,5-dibromothiophenes

A class of 3,4-diaryl-2,5-dibromothiophenes (1b-5b) was synthesized by a one-pot reaction of 3,4-diaryl-2,5-dihydrothiophenes with Br2 reagent in excellent yield (83-92%). It was found that Br2 performed a double function (oxidation and bromination) during the conversion of 3,4-diaryl-2,5-dihydrothiophenes to 3,4-diaryl-2,5-dibromothiophenes. The application of 3,4-diaryl-2,5-dibromothiophenes used as building blocks was also investigated. Employing 3,4-diphenyl-2,5-dibromothiophene (1b) as a template, a class of 2,3,4,5-tetraarylthiophenes was prepared by the Suzuki coupling reaction. This provided a new and simple approach to the preparation of 2,3,4,5-tetraarylthiophenes.     

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 .     

Ring-closing metathesis toward the synthesis of 2,5-dihydrofuran and 2,5-dihydropyrrole skeletons from Baylis-Hillman adducts

We have developed an efficient method for the synthesis of 2,5-dihydrofuran and 2,5-dihydropyrrole skeletons from the simply modified Baylis-Hillman adducts via RCM reaction.