Synthesis Of 5-tert-Butyl Benzo[b]thiophene-2-carboxylic Acid

The title compound was prepared from 4-tert-butyl cyclohexanone in high yield by a simple three step procedure.     

New methods for the synthesis of amides of benzo[b]thiophene-2carboxylic acid

The reaction of 3-bromothiocoumarin with nitrogen bases, during which the thiocoumarin system is converted to a benzothiophene system, was studied. A new method for the synthesis of amides of benzo[b]thiophene-2-carboxylic acid is proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1340–1342, October, 1978.     

alpha-phenylpropionic acid derivatives. Synthesis and dethiation of 5-benzoylbenzo[b]thiophene-3-carboxylic acid

The total synthesis of the title compound 8 started with p-thiocresol which was acylated with oxalyl chloride to give compound 1 . This product underwent a condensation reaction with chloroacetic acid under basic conditions yielding compound 2 . Two different synthetic pathways were used to convert compound 2 into the title compound 8 . The first consisted in decarboxylation of 2 to 3 , which was then converted to the ester 4 , which was brominated and the product 5 was subjected to a Friedel-Craft's reaction with benzene. The resulting benzyl derivative 6 was oxidized to the benzoyl stage i.e. compound 7 , which was finally hydrolyzed to 8 . The second pathway was similar to the first one so that the steps of esterification, bromination, Friedel-Craft's alkylation and oxidation started with the dicarboxylic acid 2 . Thus compounds 12–16 were obtained, and the last product was decarboxylated to 8 . The yields in both procedures were similar. Finally, the dethiation of compound 8 with Raney nickel afforded compounds 18, 19 and 20 .     

Reactions with benzo[b]thiophene-2,3-diones I: Synthesis of 2,3-dihydroxy-2,3-diaryl(aralkyl)benzo[b]thiophene derivatives

Benzo[b]thiophene-2,3-diones ( 1 ) react with Grignard reagents to yield 2,3-dihydroxy-2,3-diaryl(aralkyl)benzo[b]-thiophenes ( 2 ). The latter compounds yield 3,3-diaryl(aralkyl)-benzo[b]thiophene-2-ones ( 3 ) by pinacolone rearrangement. Treatment of 3 by hot ethanolic sodium hydroxide solution yields the corresponding carboxylic acids by hydrolytic heteroring opening.     

Thiophene chemistry—XXII : Some reactions of benzo[b]thiophene-2(3H)one

Benzo[b]thiophene-2(3H)one has been prepared from 2-t-butoxybenzo[b]thiophene by dealkylation. Alkylation of sodium, thallium and tetrabutylammonium salts of benzo[b]thiophene-2(3H)one produces both C- and O-alkylation along with products due to ring-opening. At elevated temperatures benzo[b]thiophene-2(3H)one reacts with HMPA (hexamethylphosphorictriamide) to give 2-dimethylaminobenzo[b]thiophene. Other 2-aminobenzo[b]thiophenes are produced by refluxing benzo[b]thiophene-2(3H)one in HMPA in the presence of excess of the corresponding amine.     

Studies on quinones. VII. Synthesis of some benzo[b]thiophene-4,7-diones

The synthesis of methyl 4,7-dihydro-4,7-dioxobenzo[b]thiophene-2-carboxylate ( 20 ) based on the reaction of methyl mercaptoacetate with activated 1,4-benzoquinones is described. Methyl 4,7-dihydro-4,7-dioxo-5-hydroxybenzo[b]thiophene-2-carboxylate ( 24 ) and its corresponding methyl ether 26 were obtained through a Thiele-Winter acetoxylation on 20 . On the basis of the properties of methyl 4,7-dihydro-4,7-dioxo-6-methoxy-benzo[b]thiophene-2-carboxylate ( 21 ) obtained from 2,4,5-trimethoxybenzaldehyde ( 32 ), the structures of the products 24 and 26 are proposed.     

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.     

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.     

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.     

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 ).     

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.     

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 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.     

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.     

Novel PdII-mediated cascade carboxylative annulation to construct benzo[b]furan-3-carboxylic acids

[reaction: see text] Benzo[b]furan-3-carboxylic acid (2) was generated from 1 by forming three new bonds in one step via a Pd(II)-mediated cascade carboxylative annulation. The proposed mechanism was supported by the observation of an unusual acetylation of 1 as a side reaction together with an (18)O-labeling study.     

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.     

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.