Synthesis of 2,5-disubstituted-3-cyanoindoles

An efficient synthesis of 2,5-disubstituted-3-cyanoindoles is described. This approach utilizes a highly selective iodination together with the modified Madelung reaction to generate an intermediate which can be readily transformed to more fully elaborated 2,5-disubstituted-3-cyanoindole templates that were previously difficult to access. Detailed examples and utility of this approach are presented herein.     

2,5-Diamidofuran anion receptors

3,4-Diphenylfuran-2,5-dicarboxylic acid bis-N-phenylamide 1 and 3,4-biphenyl-furan-2,5-dicarboxylic acid bis-N-butylamide 2 have been synthesised and shown to act as fluoride selective anion receptors in DMSO-d₆/0.5% water solution.     

Selective Synthesis of 2,5-Dimethoxy-4-nitrobenzaldehyde

A selective preparation of 2,5-dimethoxy-4-nitrobenzaldehyde is proposed in a procedure involving the transformation of the aldehyde group to a diacetoxymethyl group.     

The synthetic versatility of alkoxycarbonyl- and hydroxymethyl-piperazine-2,5-diones

Alkoxycarbonylpiperazine-2,5-diones are versatile precursors for the α-functionalisation of piperazine-2,5-diones. The alkoxycarbonyl group activates the α-carbon position to alkylation reactions and this provides a mild and selective method for the extension of the carbon framework of piperazine-2,5-diones. In addition, the alkoxycarbonyl group can be converted to the carboxy group, which in turn can be ‘deleted’ or manipulated for the installation of carbon and/or heteroatom substituents where desired, the latter via N-acyliminium chemistry. We also demonstrate that hydroxymethylpiperazine-2,5-diones complement carboxypiperazinediones as precursors for the generation of N-acyliminium ions.     

A convenient synthesis of 2,5-diaroyl-4-hydroxy cyclopent-2-enones incorporating aromatic and heteroaromatic moieties

Abstract

The base-catalyzed reaction of 1,5-diphenyl-pentane-1,3,5-trione with aromatic/heteroaromatic 1,2-diones leading to the synthesis of 2,5-diaroyl-4-hydroxycyclopent-2-enones and its conversion to 2,5-diaroylcyclopentadienones is reported here. 2,5-Dibenzoyl-4-hydroxycyclopent-2-enone and 2,5-dithenoyl-4-hydroxycyclopent-2-enone are valuable compounds which act as chemosensors for selective detection of Fe³⁺ and Cu²⁺, respectively.     

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.     

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.     

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 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.     

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.     

2，5-联苯二甲酸的新合成方法

铁粉催化下,对二甲苯于室温与溴反应,得到2－溴对二甲苯,将其制备成相应的格氏试剂,在NiCl2(PPh3)2催化下与溴苯进行交叉偶联,得到2,5－二甲基联苯,再用高锰酸钾水溶液氧化,合成标题化合物,产物的结构由IR确认。     

2,5-二甲氧基乙苯的合成方法及改进

以对苯二酚为起始原料，经醚化、傅瑞德尔-克拉夫慈反应酰化、乌尔夫-黄鸣龙反应还原制得2,5-二甲氧基乙苯，总收率达66．8％。     

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.     

Electrochemical Synthesis of 2,5-Dichloroaniline

A procedure was proposed for electrochemical reduction of 2,5-dichloronitrobenzene to 2,5-dichloroaniline in aqueous-ethanolic solution of sulfuric acid. The procedure for preparing 2,5-dichloroanilinium sulfate was optimized. The influence exerted by the cathode material, nature and amount of the organic solvent, sulfuric acid concentration, and electrolysis temperature on the yield and quality of the target product was discussed.     

Synthesis of 2,5-bis-(Ethynyl) furan Derivatives from 2,5-Furandicarboxaldehyde

A synthesis of the title compounds has been accomplished by conversion of 2,5-furandicarboxaldehyde to the dilithium salt of 2,5-bis-(ethynyl) furan followed by reaction with electrophiles.     

Synthesen an Ansabrücken von (2,5)-Pyridinophanen I

(2,5)-Pyridinophanes were chosen as model compounds for synthetic manipulations at the end of ansabridges. Some selective transformations of the carbonyl function in [11] (2,5)-Pyridinophan-11-on (1) are reported. Lactams (Ansanicotinamide), lactones, tetrazoles and other derivatives were obtained in good yield.

     

Synthesis of 2,5-diethynyl substituted oxepins from trans-1,4-diethynylcyclohexa-2,5-diene-1,4-diols

Reaction of trans-1,4-bis(trimethylsilylethynyl)cyclohexa-2,5-diene-1,4-diol with n-BuLi followed by methanesulfonyl chloride resulted in the formation of a dark red solid, which was identified as 2,5-bis(trimethylsilylethynyl)oxepin. Deprotection of the silyl groups resulted in the formation of 2,5-diethynyloxepin, a red, shock sensitive solid. Reaction of a differentially substituted cyclohexa-2,5-diene-1,4-diol gave a mixture of 2,5-diethynyl substituted oxepins.     

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.     

Synthesis of substituted hexahydro-2H-chromeno[4,3-d]pyrimidine-2,5-diones and their modification at the hydroxy group

Russian Chemical Bulletin - We proposed an approach for the preparation of substituted hexahydro-2H-chromeno-[4,3-d]pyrimidine-2,5-diones and studied their selective acylation and alkylation at the...