A simple synthesis of thieno[2,3-b]pyrazine and thieno[2,3-b] pyridine

A facile synthesis of thieno[2,3-b]pyrazine (1) and thieno[2,3-b]pyridine (9) is reported. Furthermore, convenient preparations of a variety of synthetically useful compounds derived from these ring systems is also presented.     

Synthesis of certain 5-substituted thieno[2,3-b]thiophene-2-sulfonamides and thieno[2,3-b]thiophene-2-sulfonamide 6,6-dioxides

A series of the title compounds were prepared for evaluation as inhibitors of carbonic anhydrase II. Oxidation of 5-substituted thieno[2,3-b]thiophene-2-sulfonamides provided the first examples of thiophene[2,3-b]thiophene-2-sulfonarnide 6,6-dioxides. These cyclic vinyl sulfones readily underwent addi tion to give predominately that 4,5-cis addition product.     

Mass spectra of isomeric thieno [2,3-b]- and thieno[3,2-b]pyridines

The mass spectra of six isomeric thieno- and thionaphthenopyridines were studied for the first time, and the pathways of fragmentation of the molecular ions, which made it possible to isolate the peaks of the fragment ions that characterize the destruction of the pyridine and thiophene rings, were traced. It is shown that the character and type of conjugation of the heterorings can be distinguished by analyzing the mass-spectral data. The relationship between the intensity of the peak of the doubly charged molecular ion and the number of electrons in the system and the -donor character of the heteroring was illustrated by means of the literature data on the mass spectrometry of heteroaromatic systems with one heteroatom.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 758–761, June, 1982.     

Convenient synthesis of functionalized thieno[2,3-d]pyrimidine-4-ones and thieno[2,3-b]pyridine-4-ones bearing a pyridine moiety with anticipated antioxidant activity

In the present study, ethyl 2-amino-4-methyl-5-(pyridin-2-ylcarbamoyl)thiophene-3-carboxylate (2) has been achieved using the Gewald's methodology and served as a synthon for the synthesis of various derivatives of thieno[2,3-d]pyrimidine-4-one and thieno[2,3-b]pyridine-4-one bearing a pyridine moiety via its reactions with the convenient chemical reagents. The antioxidant performance has been tested using the ABTS method and the results disclosed that thienopyrimidinone 5 and thienopyridinones 18 and 19 have the most potent antioxidant efficiency with inhibition percentage at 84.41%, 80.95%, and 76.93%, respectively, compared with ascorbic acid as a reference drug.     

Thieno [2,3 -b] pyridines and thieno [ 3,2 -b] pyridines by the method of gould-jacobs

Bis(2-, and 3-thienylammonium) hexachlorostannates were condensed with ethoxymethylene derivatives of active methylene compounds in pyridine. The resulting condensation products IVa-IVc and Va-Vc on heating under reflux in Dowtherm or diphenyl ether provided various 4-hydroxythieno[2,3-b] pyridines (Ia-Ic) and 7-hydroxythieno[3,2-b]pyridines (IIa-IIc). The compound Ic on further transformations gave yet other derivatives If-Ik.     

Facile preparation of benzo[4,5]thieno[2,3-b]pyridines and naphtho[b-4,5]thieno[2,3-b]pyridines via the reaction of Barton esters and benzynes

Titled compounds were prepared in a one-pot synthesis by generating symmetrically substituted benzyne intermediates by the diazotization of anthranilic acids in the presence of Barton esters. Unsymmetrically substituted aryne either gave mixtures of regioisomers or failed. However, nitro and methyl derivatives of titled compounds could be obtained as single products using appropriately substituted Barton esters.     

Platinum-catalyzed cyclization reaction of alkynes: synthesis of azepino[3,4-b]indol-1-ones

Novel azepino[3,4-b]indol-1-ones were synthesized from alkyne-substituted indole-2-carboxamides by catalytic intramolecular cyclization in the presence of PtCl(2). The scope and limitations of this straightforward protocol are reported.     

Synthesis of substituted thieno[2,3-b]pyrroles

A relatively simple route for synthesis of substituted thieno[2,3-b]pyrroles from readily available starting material and data for structural assignment are reported.     

First transformations of pyrano[3,4-b]indol-3-ones to salvadoricine and 2,3-diacylindoles

The readily available methylated pyrano[3,4-b]indol-3-ones 1a and 1b were hydrolyzed to furnish the 2-acetylindol-3-alkanoic acids 2 and 4 . Compound 2 was easily transformed selectively to 2-acetyl-3-methylindole ( 3 , salvadoricine). Substrate 1b reacts with molecular oxygen from the air only in the presence of a catalyst to give 2,3-diacetylindole ( 5 ) while 1a reacts with nitrosobenzene via a proposed Diels-Alder step to yield 2-acetylindole-3-carbaldehyde ( 6 ). The latter product can also be obtained in low yield from the reaction of 1a with molecular oxygen from the air.     

New method for the synthesis of substituted thieno[3,2-b]pyridines and 5H-pyrano[2,3-d]thieno[3,2-b]pyridines derived from them

A new highly selective method was developed for the synthesis of substituted thieno[3,2-b]-pyridines based on the domino reaction of monopotassium salt (rather than dipotassium one) of carbamoylcyanodithioacetic acid with ethyl 4-chloroacetoacetate. Substituted 5H-pyrano[2,3-d]-thieno[3,2-b]pyridines were synthesized based on these thieno[3,2-b]pyridines.     

Recent advances in the chemistry of thieno[2,3-b]pyridines 1. Methods of synthesis of thieno[2,3-b]pyridines

Russian Chemical Bulletin - The recent data (2007–2018) on the synthesis of thieno[2,3-b]pyridines are summarized and systematized.     

Stable polythiophene semiconductors incorporating thieno[2,3-b]thiophene

This work describes a new design methodology that allows the preparation of air stable, semiconducting thiophene polymers with high charge carrier mobilities. The incorporation of thieno[2,3-b]thiophene into a polythiophene backbone introduces cross-conjugated double bonds that disfavor full delocalization, leading to high ionization potential in comparison to a fully conjugated polythiophene, with no reduction in charge carrier mobility. The resulting solution processable polymers exhibit charge carrier mobilities up to 0.15 cm2/V s and on/off ratios greater than 105 when measured in air. Transistors exhibit lifetimes of several months in air with no encapsulation necessary.     

Nouvelles syntheses de la thieno[2,3-b] pyrazine

Two new syntheses of thieno[2,3-b]pyrazine are reported with methylpyrazine as the starting material. One of the methods consists of an original method to form a thiophene ring in condensed systems.     

Improved syntheses of thieno[2,3-b]- and [3,2-b]-fused naphthyridines

The preparation of eight isomeric thieno[2,3-b]- and [3,2-b]-fused naphthyridines [1] was improved through the Pd(0) catalyzed cross-coupling of 3-formyl-4-iodopyridine, 2-formyl-3-iodopyridine, 3-bromo-4-formylpyridine and 2-bromo-3-formylpyridine with t-butyl N-(2-trimethylstannyl-3-thienyl)car-bamate and t-butyl N-(3-trimethylstanny-2-thienyl)carbamate.     

3-Phenacylidene-3,4-dihydro-1H-pyrido[2,3-b]pyrazin-2-ones and 2-Phenacylidene-1,2-dihydro-4H-pyrido[2,3-b]pyrazin-3-ones

Condensation of 2,3-diaminopyridine ( 1 ) with ethyl o-, m- and p-substituted benzoylpyruvates 2–9 gave two isomeric products. The preferential formation of one or the other isomer has been achieved by different reaction conditions. All the products appear to exist in the enamine form as evidenced by their ¹H nmr and ir spectra.     

The preparation of 5-substituted thieno[2,3-b]furan-2-sulfonamides

An efficient synthetic route is reported for the preparation of thieno[2,3-e]furan-2-sulfonamides bearing oxygenated functionality at C-5. The method employs conversion of furan-3-carboxaldehyde to an intermediate that, in the key step, undergoes facile cyclodehydration to the fused [5,5] heterocycle under mild Knoevenagel conditions.