Synthesis and Reactivity of 5-Alkoxybenzo[b]furan-2-selenolates

By reaction of selenium(IV) oxide with 5-alkoxy-2-hydroxyacetophenone semicarbazones4-(5-alkoxy-2-hydroxyphenyl)-1'2'3-selenadiazoles were prepared. The latter readily decomposed whentreated with potassium carbonate yielding 5-alkoxybenzo[b]furan-2-selenolates. The selenolates obtainedunderwent alkylation effected by monochloroacetamide, were arylated by 2'4-dinitrochlorobenzene. Theoxidation of selenolates with iodine furnished bis(5-alkoxybenzo[b]furan-2-yl) diselenides.     

Syntheses of Benzo[b]furan-6-carbonitrile and 6-Cyanobenzo[b]furan-2-boronic Acid Pinacol Ester

6-Cyanobenzo[b]furan-2-boronic acid pinacol ester (10) is a potentially useful two-point scaffold for the construction of specific compounds or compound libraries with benzofuran cores. Using a per-iodination/de-iodination strategy coupled with Sonogashira alkynylation and Cu-catalyzed heteroannulation, we have developed a procedure that allows the preparation of benzo[b]furan-6-carbonitrile (9) and 6-cyanobenzo[b]furan-2-boronic acid pinacol ester (10) in gram quantities.

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Condensed heterocycles. 42. Synthesis and some properties of 3-hydroselenobenzo[b]furan-2-carbaldehyde and 2-hydroselenobenzo[b]furan-3-carbaldehyde

The reactions of 3-chlorobenzo[b]furan-2-carbaldehyde and 2-bromobenzo[b]furan-3-carbaldehyde with sodium hydrogen selenide have yielded isomeric hydroseleno aldehydes which, under the action of atmospheric oxygen, have oxidized to diselenides, while alkylation of the seleno aldehydes with methyl iodide leads to the formation of the corresponding methylseleno derivatives.For communication 41, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1177–1179, September, 1984.     

Preparation of Cyan Dyes from 6-Diethylaminobenzo[b]furan-2-carboxaldehyde

6-Diethylaminobenzo[b]furan-2-carboxaldehyde was synthesized in four steps and 48% overall yield starting from 4-diethylaminosalicylaldehyde. Five cyan dyes were made from this aldehyde using malononitrile dimer and 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran. The crystal structures of two dyes are included.     

(苯并呋喃-2-酰基)二茂铁衍生物的合成与表征

氯乙酰基二茂铁(1)与水杨醛或取代水杨醛在聚乙二醇-400作相转移催化剂条件下,使Williamson反应与Knoevenagel反应在一锅内完成,以40.2%～70.0%的总收率得到了由羰基相连的二茂铁与苯并呋喃组成的结构新颖的闭环产物(苯并[b]呋喃-2-酰基)二茂铁衍生物2a～2n.通过IR,1HNMR,MS和元素分析确认了所合成新化合物2a～2n的结构.     

Base-assisted intramolecular 6-acetoxypyranone-acetylene [5+2] cycloaddition. Synthesis and reactivity of novel oxa-tricyclo[5.3.1.0]undecenones

The synthesis of 3,11-dioxatricyclo[5.3.1.0^1,5]undeca-5,9-dien-8-ones is reported from suitable 5-substituted furfuryl alcohols bearing an acetylenic side-chain. Successive peracid-mediated oxidative rearrangement of furan carbinols and base-assisted intramolecular 1,3-dipolar cycloaddition afforded oxygen-bridged tricyclo-undecane derivatives. Stereoselective transformations of cycloadducts are also discussed.     

Benzo[b] thiophene derivatives. XXII. Synthesis of the isomeric 5-methyl-6-methoxy- and 5-methoxy-6-methylbenzo[b] thiophene-2-carboxylic acids

The two isomeric benzo[b] thiophene-2-carboxylie acids having methyl and methoxy groups at positions 5 and 6 have been prepared and characterized. Both acids have been decarboxylated to the corresponding isomeric 5,6-disubstituted benzo[b]thophenes, and esterified to their methyl esters. The intermediate rhodanines, α-mercaptocinnamic acids and corresponding disulfides are described. An unusual by-product in the oxidative cyclization of β-3-methyl-4-methoxyphenyl-α-mercaptoacrylic acid with iodine is shown to be trans-3-methyl-4-methoxycinnamic acid, which can also be formed directly from the mercaptoacrylic acid by reduction with hydrogen iodide.     

Synthesis and reactivity of [2]disilaniobocenophanes

The paramagnetic ansa-niobocene [(Me₂Si)₂(η⁵-C₅H₄)₂NbCl₂] (1) was obtained from the reaction of Li₂[(Me₂Si)₂(C₅H₄)₂] with [NbCl₄(thf)₂]. Further treatment with Li[AlH₄] yielded [(Me₂Si)₂(η⁵-C₅H₄)₂NbH₃] (3), which is prone to decomposition within a few days at room temperature both in solution and in the solid-state, thus affording primarily an insoluble black material. However, after heating or irradiation of a solution of 3 small quantities of the dimeric niobium hydride species, [(Me₂Si)₂{μ-(η¹:η⁵-C₅H₃)}(η⁵-C₅H₄)NbH]₂ (4), were isolated and characterized by X-ray diffraction.     

Synthesis of donor-acceptor chromophores by the [2 + 2] cycloaddition of arylethynyl-2H-cyclohepta[b]furan-2-ones with 7,7,8,8-tetracyanoquinodimethane

Arylethynyl-2H-cyclohepta[b]furan-2-ones reacted with 7,7,8,8-tetracyanoquinodimethane (TCNQ) in a formal [2 + 2] cycloaddition reaction, followed by ring opening of the initially formed cyclobutene derivatives, to afford the corresponding dicyanoquinodimethane (DCNQ) chromophores in excellent yields. The intramolecular charge-transfer (ICT) interactions between the 2H-cyclohepta[b]furan-2-one ring and DCNQ acceptor moiety were investigated by UV/Vis spectroscopy and theoretical calculations. The redox behavior of the novel DCNQ derivatives was examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their multistep electrochemical reduction properties depended on the number of DCNQ units in the molecule. Moreover, a significant color change was observed by visible spectroscopy under electrochemical reduction conditions.     

Synthesis of Chiral Tetrahomodiazacalix[4]-and [6]Arenes Bridged by Cystine Peptide

Bicyclic tetrahomodiazacalix[4]- and [6]arenes bridged by a cystine peptide were easily synthesized from the cyclization reactions of bis(chloromethyl)phenol-formaldehyde oligomers with cystine peptides in DMF in moderate yields.     

The reaction of 2-arylsulfonyloxytropones and active methylene compounds The formation of 8-hydroxy-2H-cyclohepta[b]furan-2-one and 2-amino-8H-cyclohepta[b]furan-8-one derivatives

Reaction of 2-arylsulfonyloxytropones (IV) and active methylene compounds, diethyl malonate, ethyl acetoacetate, ethyl cyanoacetate, malononitrile or cyanoacetamide, in the presence of NaOEt give 8-hydroxy-2H-cyclohepta[b]furan-2-one derivatives (V) and/or 2-amino-8H-cyclohepta[b]furan-8-one derivatives (VII), in addition to azulene derivatives (1) or 2H-cyclohepta(b]furan-2-one derivatives (II), known to be obtained by the reaction of 2-chlorotropones or 2-methoxytropones with active methylene compounds. Relative yields of products are influenced markedly by conditions, e.g. base type or molar ratios. The formation of V and VII is characteristic of 2-arylsulfonyloxytropones, not being observed with 2-chlorotropones or 2-methoxytropones. A reaction course involving elimination of the arylsulfonyl group as arenesulfinate ion is presented.     

Synthesis of 6-phenylthiobenzo[b]thiophenes

A method of synthesizing 2-acetylamino-7-hydroxy-6-phenylthio-3-carbethoxybenzo[b]thiophenes from 6-phenylthio-7-oxo-4,5,6,7-tetrahydrobenzo[b]thiophenes has been developed. A method is also proposed for synthesis of 7-phenylthiobenzothieno[2,3-d]pyrimidines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 534–536, April, 1991.     

Synthesis of benzo[b]furan-2-thioles from 4-(2-hydroxyaryl)-1,2,3-thiadiazoles

4-(2-Hydroxyaryl)-1,2,3-thiadiazoles treated with bases decompose with nitrogen liberation and the formation of benzo[b]furan-2-thiolates. On acidifying the thiolates benzo[b]furan-2-thiols were obtained. 4-(4- and -5-Benzyloxy-2-hydroxyphenyl)-1,2,3-thiadiazoles formed analogously the corresponding benzo[b]furan-2-thiolates whose acidifying afforded polymeric compounds.