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.     

Indolobenzo[b] furans. 2. Some indolo[5,6-d]- and indolo[5,4-d] benzo[b]furans

The reactivities of new heterocyclic systems, viz., indolo [5,6-d]- and indolo[5,4-d]benzo[b]furans, in several electrophilic-substitution reactions (the Mannich and Vilsmeier reactions and acylation) were studied. It was established that the indicated heterocycles, like indole, are readily formylated and aminomethylated; some anomalies are observed only in the case of acylation.See [1] for Communication 1.Translated from Kihimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 355–358, March, 1985.     

Synthesis of benzo[b]furans via CuI-catalyzed ring closure

A wide variety of benzo[b]furans were synthesized efficiently via a CuI-catalyzed ring closure of 2-haloaromatic ketones. The methodology was tolerant to various functional groups, affording benzofurans in 72-99% yields.     

A multi-component coupling approach to benzo[b]furans and indoles

A single step access to multiply substituted benzo[b]furans and indoles has been developed.     

New benzo[b]furans as electroluminescent materials for emitting blue light

[structure: see text] New functionalized mono- and bis-benzo[b]furan derivatives were synthesized and developed as blue-light emitting materials. They possessed a CN, CHO, CH=CHPh, CH=CPh(2), or CH=CHCOOH group at the C4-position. Two benzo[b]furan nuclei in bis-benzo[b]furan derivatives were connected by a divinylbenzene bridge. With good volatility and thermal stability, bis-benzo[b]furan 7a was fabricated as a device. It emitted blue light with brightness 53430 cd/m(2) (at 15.5 V) and high maximum external quantum efficiency 3.75% (at 11 V).     

2-Amino-3-(benzimidazol-2-yl)benzo[b]furans

The corresponding 2-amino-3-(benzimidazol-2-yl)benzo[b]furans were obtained by reaction of 2,3,5-trimethyl-1,4-benzoquinone with 2-cyanomethylbenzimidazoles. It is shown that new benzo[b]furo[2′,3′∶4,5]pyrimido[1,6-a]benzimidazole polynuclear heterocyclic systems (bases and quaternary salts) are formed in the reaction of these products with acylating agents. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 164–166, February, 1980.     

Enantioselective straightforward access to benzo[b]thiophene analogs of Azatoxin

Horner-Wadsworth Emmons olefination followed by asymmetric hydrogenation allowed the first synthetic access to the chiral thiotryptophan with good enantiomeric excess. Oxazolidinone formation followed by a Pictet–Spengler condensation provided the benzothiophenic analog of Azatoxin.     

A new and efficient synthesis of 4-functionalized benzo[b]furans from 2,3-dihalophenols

Tandem Sonogashira coupling/5-endo-dig cyclization reactions on 2,3-dihalophenols suppose a straightforward entry to 4-halobenzo[b]furans, which can be easily transformed into 4-functionalized benzo[b]furans, that are difficult to synthesize by other procedures. On the other hand, the starting 2,3-dihalophenols are efficiently prepared from commercially available 3-halophenols, via their N,N-diethyl carbamates by selective lithiation at the 2-positions by treatment with s-BuLi/TMEDA or LDA at low temperature and reaction with halogen electrophilic reagents.     

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 ).     

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.     

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.     

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.     

K-region oxides and imines of benzo[b]phenanthro[2,3-d]thiophene and benzo[b]phenanthro[3,2-d]thiophene

The syntheses of the K-oxides and K-imine derivatives of benzo[b]phenanthro[2,3-d]thiophene and benzo-[b]phenanthro[3,2-d]thiophene are described. The parent hydrocarbons 1 and 2 were oxidized with osmium tetroxide and sodium metaperiodate, and the dialdehydes 12 and 18 so formed, cyclized to the corresponding epoxides 1a,12b-dihydrobenz[b]oxireno[9,10]phenanthro[2,3-d]thiophene ( 7 ) and 1a,12b-dihydrobenz-[b]oxireno[9,10]phenanthro[3,2-d]thiophene ( 13 ). Reaction of the oxiranes with sodium azide gave mixtures of azido-alcohols that, in turn, were transformed to the thiaarene imines 1a,12b-dihydro-1H-benz[b]azirino-[9,10]phenanthro[2,3-d]thiophene ( 8 ) and 1a,12b-dihydro-1H-benz[b]azirino[9,10]phenanthro[3,2-d]thiophene ( 14 ), respectively, with the aid of tri-n-butylphosphine.     

New synthesis of 2-aryl-3-substituted benzo[b]furans from benzyl 2-halophenyl ethers

Treatment of benzyl 2-halophenyl ethers with 3 equiv of t-BuLi results in Li-halogen exchange and lithiation at benzylic methylene simultaneously. These dianions do not undergo Wittig rearrangement and can be trapped with electrophiles. Their reactions with carboxylic esters afford the corresponding 2-aryl-3-hydroxy-2,3-dihydrobenzo[b]furans as a mixture of diastereoisomers. Subsequent acid-catalyzed or mediated dehydration gives moderate to good overall yield of a variety of 2-aryl-3-substituted benzo[b]furans.     

Synthesis of anthra[b]thiophenes and benzo[b]naphtho[d]thiophenes

All isomers of the parent anthra[b]thiophenes and benzo[b]naphtho[d]thiophenes, namely anthra[2,3-b]thio-phene, anthra[2,1-b]thiophene, anthra[1,2-b]thiophene, benzo[b]naphtho[2,3-d]thiophene, benzo[b]naphtho[2,1-d]thiophene and benzo[b]naphtho[1,2-d]thiophene were synthesized using a new procedure.     

Condensed pyridine bases synthesis of some benzo[b]furo[2,3-c]-, benzo[b]- thieno[2,3-c]-, and benzo[b]selenopheno[2,3-c]-quinolines

Summary Condensation of benzo[b]furan-3(2H-one, benzo[b]thiophen-3(2H)-one and benzo[b]selenophen-3(2H)-one with dimedone gives 2-(3-heteryl)dimedones. Acylation of the latter leads to the corresponding tetracyclic pyrylium salts, from which condensed quinolines are obtained. Some condensed quinoline derivatives are obtained by reaction of 1-oxo-1,2,3,4-tetrahydroheterene[2,3-c]quinolines with sodium borohydride, hydrazine, and hydroxylamine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 321–326, March, 1994.     

Chemistry of benzo[b]selenophene

The bromination of benzo[b]selenophene with an equimolecular amount of bromine and its acetylation with acetic anhydride in the presence of boron trichloride etherate proceed to form a mixture of isomeric 2- and 3-substituted derivatives; 2,3-dibromobenzo[b]selenophene is formed on bromination with two equivalents of bromine. Benzo[b]selenophene-2-carboxylic acid, its acid chloride and methyl ester, as well as 2-acetylbenzo[b]selenophene, were synthesized from the lithium derivative of benzo[b]selenophene.See [1] for communication III.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 15–19, January, 1972.     

Stereochemistry of benzo[b]quinuclidines

The PMR spectra of several 3- and 2,3-substituted benzo[b]quinuclidines were studied. It is shown that the following can be used to establish the configurations of this series of compounds: the differences in the chemical shifts of the protons of the quinuclidine ring in the syn and anti orientations relative to the benzene ring, the shift in the signals of the protons of the alkyl groups of a substituent relative to the signals of the same protons in the analogous quinuclidine derivative, and the stereospecificity of the long-range, spin-spin interaction constants of the protons of the quinuclidine ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 981–986, July, 1971.