Electronic structure and reactivity of guanylthiourea: A quantum chemical study

Electronic structure analysis of guanylthiourea (GTU) and its isomers has been carried out using quantum chemical methods. Two major tautomeric classes (thione and thiol) have been identified on the potential energy (PE) surface. In both the cases conjugation of pi‐electrons and intramolecular H‐bonds have been found to play a stabilizing role. Various isomers of GTU on its PE surface have been analyzed in two different groups (thione and thiol). The interconversion from the most stable thione conformer ( GTU‐1 ) to the most stable thiol conformer ( GTU‐t1 ) was found to take place via bimolecular process which involves protonation at sulfur atom of GTU‐1 followed by subsequent C? N bond rotation and deprotonation. The detailed analysis of the protonation has been carried out in gas phase and aqueous phase (using CPMC model). Sulfur atom (S1) was found to be the preferred protonation site (over N4) in GTU‐1 in gas phase whereas N4 was found to be the preferred site of protonation in aqueous medium. The mechanism of S‐alkylation reaction in GTU has also been studied. The formation of alkylated analogs of thiol isomers (alkylated guanylthiourea) is believed to take place via bimolecular process which involves alkyl cation attack at S atom followed by C? N bond rotation and deprotonation. The reactive intermediate RS(NH₂)C? N? C(NH₂)₂⁺ belongs to the newly identified ^⊕N(←L)₂ class of species and provides the necessary dynamism for easy conversion of thione to thiol. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Synthesis and structure of 2-hydroxy-3-formylbenzo[b]thiophene azomethines

A number of 2-hydroxy-3-formylbenzo[b]thiophene azomethines and their derivatives, which model the individual tautomeric forms, were synthesized. As a result of a study of the electronic, vibrational, and PMR spectra, a ketone-amine structure, the stability of which is confirmed by quantum-mechanical calculations of the atomization energies of the individual tautomeric forms calculated by the Pariser-Parr-Pople (PPP) method within the Dewar , parametrization, was assigned to these azomethines.Communication XVIII from the series Benzoid—Quinoid Tautomerism of Azomethines and Their Structural Analogs. See [1] for communication XVII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 635–642, May, 1975.     

The unusual structure of 3-hydro-2-acetylbenzo[b]thiophene hydrazones

The structure of N,N-disubstituted 3-hydroxy-2-acetylbenzo[b]thiophene hydrazones was investigated by x-ray structural analysis. 2-(N-Methyl-N-phenylhydrazinoethylidene)-3(2H)-benzo[b]thiophenone exists in the E-ketoenehydrazine form, and 2-(N,N-diphenylhydrazinoethylidene)-3(2H)-benzo[b]thiophenone in the crystals forms a structure intermediate between the ketoenehydrazine and hydroxyhydrazone forms.Institute of Chemical Physics in Chernogolovka, Russian Academy of Sciences, Chernogolovka 142432. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 917–922, April, 1992.     

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.     

Synthesis and structure of anils of 2-formyl-3-mercaptobenzo[b]thiophene and 2-formyl-3-mercaptobenzofuran

As a result of a study of the electronic, vibrational, and PMR spectra of alkyl- and arylimines of 2-formyl-3-mercaptobenzo[b]thiophene and 2-formyl-3-mercaptobenzofuran and of the spectra of model compounds the thione-enamine structure was assigned to the imines. The stability of the latter structure is in agreement with the results of quantum-mechanical calculations of the energies of atomization of the individual tautomeric forms; the calculations were made by means of the Pariser-Parr-Pople (PPP) method with the Dewar σ, π parametrization.     

3-Aminoalkyl-5-methyl-benzo[b]thiophene

Zusammenfassung Ausgehend von -[5-Methyl-benzo[b]thienyl-(3)]-propionsäure wurde eine Reihe von 5-Methyl-benzo[b]thiophenen mit einer Aminoalkylsubstitution in 3-Stellung dargestellt: 3-(-Aminoäthyl)-5-methyl-benzo[b]thiophen durchCurtius-Abbau des Azids und 3-(-Aminopropyl)-5-methyl-benzo[b]thiophen sowie N-Substitutionsprodukte davon durch LiAlH₄-Reduktion der entsprechenden Amide.

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5-Methyl-benzo[b]thiophenes having an aminoalkyl substituent in position 3 were prepared from -[5-methyl-benzo[b]-thienyl-(3)]-propionic acid: 3-(-aminoethyl)-5-methyl-benzo[b]-thiophene byCurtius rearrangement of the azide, and 3-(-aminopropyl)-5-methyl-benzo[b]thiophene as well as some of its N-derivatives by reduction of the corresponding amides with LiAlH₄.

     

Benzo[b]thiophene derivatives. XXVI. 5-methoxy-6-chloro-3-β-acetamidoethylbenzo[b ]thiophene,a blocked analog of melatonin

A potential anti-ovulatory agent, 5-methoxy-6-chloro-3-β-acetamidoethylbenzo[b]thiophene, a sulfur analog of melatonin having the 6-position blocked to inhibit oxidative metabolism, has been synthesized from 3-hydroxy-4-chloroacetophenone.     

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.     

N-Substituierte 2-Methyl-3-aminoacetyl-benzo[b]thiophene und 2-Methyl-3-(α-hydroxy-β-amino-äthyl)-benzo[b]thiophene

Zusammenfassung Bromierung von 2-Methyl-3-acetyl-benzo[b]thiophen ergab 2-Methyl-3-bromacetyl-benzo[b]thiophen, das beim Umsetzen mit Dimethylamin, Morpholin und N-Methylpiperazin die entsprechend basisch substituierten 3-Acetylverbindungen lieferte. Diese wurden mit LiAlH₄ zu den -Hydroxyverbindungen reduziert.In ähnlicher Weise wurde auch 3-Diäthylaminoacetyl-benzo[b]thiophen dargestellt.

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Bromination of 2-methyl-3-acetyl-benzo[b]thiophene gave 2-methyl-3-bromacetyl-benzo[b]thiophene, which reacted with dimethylamine, morpholine and N-methylpiperazine to give the corresponding base-substituted 3-acetyl derivatives. These were reduced by LiAlH₄ to the -hydroxy compounds.Similarily 3-diethylaminoacetyl-benzo[b]thiophene was synthesized.

     

The structure of thiophene sesquioxide: Syn,endo-3a,4,7,7a-tetrahydro-4,7-epithiobenzo[b] thiophene 1,1,8-trioxide

Thiophene sesquioxide is shown to be syn, endo-3a,4,7,7a-tetrahydro-4,7-epithiobenzo[b]-thiophene 1,1,8-trioxide (I) by ¹ H and ¹³ C nmr evidence. Assignment of the ¹³ C spectrum was facilitated by a cross-ring long-range ¹³ C-¹ H coupling. The mass spectrum of I is dominated by an unusual break-down to give benzene radical cation.     

Synthesis and structure of derivatives of 7-aminobenzo[b]thiophene

Oximes of 2-acylamino-3-ethoxycarbonyl-7-oxo-4,5,6,7-tetrahydrobenzo[b]thiophenes have been prepared. A method for the synthesis of derivatives of 7-aminobenzo[b]thiophene is proposed and the hydrolysis of the compounds prepared has been studied.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1178–1180, September, 1986.     

Acylation of 3-acyl-2-methylbenzo[<Emphasis Type=Italic>b</Emphasis>]thiophene

The effect of the nature of the catalysts, reagents, and solvents on the acylation of 3-acyl-2-methyl-benzo[b]thiophene was studied. The structure of the products was supported by the two-dimensional ¹H and ¹³C NMR spectra (2D, HMBC).     

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.