Derivatives of benzo[b]furan. Part II. Structural studies of derivatives of 2- and 3-benzo[b]furancarboxylic acids

Structural Chemistry - The selected derivatives of the 2- and 3-benzo[b]furancarboxylic acids were synthesized and their structures were studied using the X-ray crystallography and the...     

1H NMR spectra of benzo[b]furan,benzo[b]thiophene and benzo[b]selenophene oriented in a lyotropic mesophase

The proton nuclear magnetic resonance spectra of benzo[b]-furan, -thiophene and -selenophene oriented in a potassium laurate lyotropic liquid crystal have been analyzed. Geometrical information has been obtained and compared to previous thermotropic results and various hypothetical models.     

Sulfur-rich heterocycles from 2-metalated benzo[b]thiophene and benzo[b]furan: synthesis and structure

The reaction of 2-lithiated benzo[b]thiophene with 8 equiv of elemental sulfur was found to give pentathiepino[6,7-b]benzo[d]thiophene. In contrast, treatment of 2-lithiated benzo[b]furan with sulfur under similar conditions produced the interesting ring system bis(benzo[4,5]furo)[2,3-e:3',2'-g][1,2,3,4]tetrathiocine. Both of these new cyclic polysulfides were studied by X-ray crystallography. Two polymorphic forms of pentathiepino[6,7-b]benzo[d]thiophene were found, displaying similar conformations but different packing schemes, which was also evident from powder diffraction data.     

2-取代芳基苯并呋喃类化合物的合成

以香草醛和丙二酸为原料,经Knoevenagel缩合、酯化、仿生氧化偶联、DDQ脱氢、还原和氧化等反应合成了3种新的2-取代芳基苯并呋喃类化合物,其结构经1H NMR,IR和MS表征。两分子阿魏酸甲酯仿生氧化偶联为它的二聚体是合成的关键步骤。     

1H NMR spectra of the 2-trifluoroacetyl derivatives of benzo[b]furan and benzo[b]thiophene

The ¹H NMR spectra of the 2-trifluoroacetyl derivatives of benzo[b]furan and benzo[b]thiophene were recorded at 200MHz in two solvents, chloroform and acetone. A long-range coupling constant, 5J(HF), between the fluorine nuclei of the trifluoroacetyl group and H-3, of a value higher than 1 Hz, was measured. From the comparison of the ¹H chemical shifts of, and the solvent effects on, the trifluoroacetyl compounds and those of the corresponding 2-acetyl derivatives, and on the basis of an empirical interpretation of the ⁵J(HF) coupling constant, a predominant Z conformation was tentatively assigned to these derivatives.     

Parallel synthesis of a multi-substituted benzo[b]furan library

The solution-phase parallel synthesis of a 121-member library of multi-substituted benzo[ b]furans is described. 2,3,5-Trisubstituted benzo[ b]furans have been prepared by the palladium-catalyzed substitution of 3-iodobenzofurans by Suzuki-Miyaura, carbonylative Suzuki, Sonogashira, Heck, and carboalkoxylation chemistry. The 3-iodobenzofurans are readily prepared in good to excellent yields by the palladium/copper-catalyzed cross-coupling of various o-iodoanisoles and terminal alkynes, followed by electrophilic cyclization with ICl.     

NMR spectrum of benzo[b]furan in a nematic phase

The proton NMR spectrum of benzo[b]furan has been investigated in the nematic phase of a liquid crystal. Dipolar couplings obtained from the spectral analysis have been used to derive the interproton distance ratios. The phenyl ring geometry differs from that in benzo[b]thiophene. The deviations have been explained in terms of bond polarization effects.     

新型2-苯甲酰基苯并呋喃类似物的合成

以水杨醛与2-溴-4’-氟苯乙酮为原料,经取代和分子内缩合反应合成了中间体2-苯甲酰基苯并呋喃(1);在碱性条件下,1分别与咪唑,N-甲基哌嗪和二乙胺等反应,合成了6个新型的2-苯甲酰基苯并呋喃含氮类似物,收率63%~82%,其结构经1H NMR,13C NMR,IR和HR-MS表征。     

Copper catalysis in the construction of indole and benzo[b]furan rings

This perspective reports on some of the main copper-catalyzed routes to the construction of the pyrrole and furan rings incorporated into the indole and benzo[b]furan systems, respectively. The first part illustrates the synthesis of indoles through cyclizations of 2-alkynylanilid(n)es, preformed or generated in situ, and cyclizations via intramolecular N-arylation, N-vinylation, and C-C bond forming reactions. The second part illustrates the synthesis of benzo[b]furans through cyclizations of preformed 2-alkynylphenols, domino synthesis of 2-alkynylphenols/cyclization processes, and cyclizations via intramolecular O-arylation reactions.     

Palladium-catalyzed intramolecular O-arylation of enolates: application to benzo[b]furan synthesis

[reaction: see text] A catalyst generated from Pd2(dba)3 and the ligand DPEphos effects intramolecular C-O bond formation between enolates and aryl halides in the conversion of 1-(2-haloaryl)ketones directly into the corresponding benzofurans. Both cyclic and acyclic ketones are efficient substrates. Thio ketones can also be employed allowing the preparation of the corresponding benzothiophenes.     

Toluene dioxygenase-catalyzed cis-dihydroxylation of benzo[b]thiophenes and benzo[b]furans: synthesis of benzo[b]thiophene 2,3-oxide

Enzymatic cis-dihydroxylation of benzo[b]thiophene, benzo[b]furan and several methyl substituted derivatives was found to occur in both the carbocyclic and heterocyclic rings. Relative and absolute configurations and enantiopurities of the resulting dihydrodiols were determined. Hydrogenation of the alkene bond in carbocyclic cis-dihydrodiols and ring-opening epimerization/reduction reactions of heterocyclic cis/trans-dihydrodiols were also studied. The relatively stable heterocyclic dihydrodiols of benzo[b]thiophene and benzo[b]furan showed a strong preference for the trans configuration in aqueous solutions. The 2,3-dihydrodiol metabolite of benzo[b]thiophene was utilized as a precursor in the chemoenzymatic synthesis of the unstable arene oxide, benzo[b]thiophene 2,3-oxide.     

New reaction of benzo[b]thieno[3,2-b]benzo[b]thiophene disulfone

A new reaction of benzo[b]thieno[3,2-b]benzo[b]thiophene disulfone with amines that takes place with opening of one of the thiophene rings and nucleophilic substitution in the heteroaromatic ring at the site of cleavage of the S-C bond was observed. The molecular structures of the products of amination of the disulfone were determined by x-ray diffraction analysis. Hydrolysis and dehydration of the amination products gave derivatives of a new heterocyclic system, viz., benzo[b]-thieno[3,2-e]benzo[c]-1,2-oxathiin. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 320–323, March, 1980.     

The synthesis of benzo[b]phenanthro[d]thiophenes and anthra[b]benzo[d]thiophenes

The synthesis of benzo[b]phenanthro[2, 3-d]thiophene ( 5 ), benzo[b]phenanthro[4, 3-d]thiophene ( 6 ), benzo-[b]phenanthro[2, 1-d]thiophene ( 9 ), benzo[b]phenanthro[3, 2-d]thiophene ( 14a ), anthra[1, 2-b]benzo[d]thiophene ( 24 ), anthra[2, 3-b]benzo[d]thiophene ( 29 ) and anthra[2, 1-b]benzo[d]thiophene ( 30 ) is described as well as the preparation of 13-methylbenzo[b]phenanthro[3, 2-d]thiophene ( 14b ).     

Solid-phase synthesis of 2,3-disubstituted benzo[b]thiophenes and benzo[b]selenophenes

A concise and efficient solid-phase synthesis of benzo[b]thiophenes and benzo[b]selenophenes based on a combination of palladium-mediated coupling and iodocyclization protocols has been developed.     

Synthesis and aldose reductase-inhibitory activity of benzo[b]furan derivatives possessing a carboxymethylsulfamoyl group

Various benzo[b]furan derivatives with a carboxymethylsulfamoyl group were prepared and evaluated for aldose reductase-inhibitory potency. Most of the compounds displayed significant inhibitory activities (IC50, 10(-8)-10(-7) M). Among the test compounds, the compounds having a carboxymethylsulfamoyl group at the 3- or 4-position exhibited the greatest inhibitory potency. Structure-activity trends of the tested compounds are discussed.     

2-(2,6-二烷氧基苯基)苯并呋喃衍生物的合成

以焦性没食子酸、4-羟基苯甲醛和酚为原料, 以邻碘代苯酚与苯乙炔衍生物的Sonogashira偶联及其连串化反应生成苯并呋喃环为关键步骤, 设计合成了一系列2-(2 ,6 -二烷氧基苯基)苯并呋喃衍生物, 并对产物进行了¹H NMR, ¹³C NMR, MS等表征.     

Chemistry of benzo[b]furan. V.. Synthesis of substituted thia-analogs and oxa-analogs of dihydrorutecarpine and evodiamine

Cycloaddition of 3,4-dihydrobenzo[b]thieno[2,3-c]pyridine ( 6 ) with the sulfinamide anhydride 9 (R = H) afforded the thia-analog of dihydrorutecarpine ( 2a ). Condensation of the imine 6 with the sulfinamide anhydride 9 (R = CH₃) gave the thia-analog of evodiamine ( 2b ). Starting from 1-methyl-3,4-dihydrobenzo[b]thieno[2,3-c]pyridine ( 12 ) and 1-methyl-3,4-dihydrobenzo[b]furo[2,3-c]pyridine ( 14 ), a series of 3-methyl derivatives of thia-analogs of dihydrorutecarpine and evodiamine ( 2c-2i ) and oxa-analogs of dihydrorutecarpine and evodiamine ( 1a-1g ) were similarly prepared.     

On-water chemistry: copper-catalyzed straightforward synthesis of benzo[b]furan derivatives in neat water

[reaction: see text] A more sustainable protocol leading to 2-alkyl- or 2-aryl-substituted benzo[b]furans is reported, involving a copper-TMEDA complex which catalyzes the transformation of readily available ketone derivatives into the corresponding benzofurans in good to excellent yields. The reaction is accomplished using water as the solvent without organic cosolvents, and one example of catalyst reutilization is also presented.