Formation Of Thiophene Ring Research Articles

Domino reactions of thiopyrano[4,3-b]indole-3(5H)-thiones and dimethyl acetylenedicarboxylate: Quantum chemical investigation and experiment

Reaction of thiopyrano[4,3-b]indole-3(5H)-thiones and dimethyl acetylenedicarboxylate (DMAD) proceeds via two competing cascade pathways. Initially, both the pathways begin from thiocarbonyl sulfur and acetylene carbon atoms interaction. Then two parallel processes take place: an alkyne–thiocarbonyl metathesis and a (3 + 2) cycloaddition. In the next stages, in both cases, thiophene ring formation and thiopyran ring opening proceed. Finally, (4 + 2) cycloaddition reactions of intermediate thioketones and a second equivalent of DMAD leads to the resulting thiopyrano[4,3-b]indole derivatives bearing thienyl substituent. The kinetic and thermodynamic characteristics of both pathways were compared on the basis of DFT and ab initio 6-311++G(d,p) quantum chemical calculations.

In situ generated reagent from sulfur for alkynylanthraquinone cyclization. The simple synthesis of angular thienoanthraquinones

A new strategy for thiophene ring formation via the direct CH cyclization of 1-alkynyl-9,10-anthra(4-alkynyl-1-aza-9,10-anthra)quinones to give the corresponding thienoanthraquinones has been developed. A highly effective sulfinating agent was generated in situ by the reaction of elemental sulfur and alkali. It was also shown that this reagent is effective in the cyclization reaction with replacement of the chlorine atom.

Low-Cost Synthesis and Physical Characterization of Thieno[3,4-c]pyrrole-4,6-dione-Based Polymers

The improved synthesis of thieno[3,4-c]pyrrole-4,6-dione (TPD) monomers, including Gewald thiophene ring formation, a Sandmeyer-type reaction, and neat condensation with an amine, is presented. This protocol enables faster, cheaper, and more efficient preparation of TPD units in comparison to traditional methods. Furthermore, a series of TPD homo- and pseudohomopolymers bearing various alkyl chains was synthesized via a direct heteroarylation polymerization (DHAP) procedure. UV-visible absorption and powder X-ray diffraction measurements revealed the relationship between the ratio of branched to linear alkyl chains and the optoelectronic properties of the polymers as well as their packing in the solid state.

Reactions of heterocumulenes with organometallic reagents: XVIII. Quantum-chemical study on the mechanisms of formation of thiophene ring from lithium and potassium buta-2,3-dienimidothioates

Thermodynamic stabilities of different isomers and tautomers of lithium and potassium buta-2,3-dienimidothioates (ambident N,S-centered anionic adducts derived from methoxyallenyl carbanion and methyl isothiocyanate) as real or potential precursors of 3-methoxy-N,N-dimethylthiophen-2-amine were estimated by quantum-chemical calculations in terms of the density functional theory. Gradient channels corresponding to concerted (one-step) and stepwise (two-step) mechanisms of formation of thiophene ring from the most stable conformers and tautomers were localized. The formation of thiophene structure from lithium and potassium buta-2,3-dienimidothioates in two steps via intramolecular cyclization to thiophen-2(5H)-ylidene anion and its isomerization into thienylamide was found to be more probable. The activation barriers in both stepwise and concerted cyclization mechanisms considerably decrease in going from lithium to potassium as counterion.

Synthesis of Benzo[2,1-b:3,4-b’]dithiophene-4,5-dione Derivatives

The 1-trimethylsilylimidazole-mediated thiophene ring formation from 6-acylbenzo[b]thiophene-4,5-diones (3), which were prepared utilizing photoacylation of benzo[b]thiophene-4,5-dione (1) with aliphatic aldehydes, and ethyl mercaptoacetate, followed by acid hydrolysis and oxidation with cerium(IV) ammonium nitrate (CAN), led to one-pot formation of the 3-substituted ethyl 4,5-dioxo-4,5-dihydrobenzo[2,1-b:3,4-b'jdithiophene-2-carboxylates (4) in satisfactory yields.

Concise Route to 4,5-Dioxo-4,5-dihydronaphtho[1,2-b]thiophene-2-carboxylates

Reactions of 3-acyl-1,2-naphthoquinones with ethyl mercaptoacetate followed by protection of the resulting hydroxyl groups and thiophene ring formation using 1-trimethylsilylimidazole, deprotection with hydrochloric acid,and oxidation with cerium(lV) ammonium nitrate (CAN) gave, in one-pot, the title thienonaphthoquinone derivatives in moderate to good yields.

Synthesis of thieno[2,3-b]quinoxalines and pyrrolo[1,2-a]quinoxalines from 2-haloquinoxalines

The palladium(0)-catalysed coupling of 2-haloquinoxalines with functionally substituted alkynes, addition of one mol equivalent of bromine to the 2-alkynylquinoxalines thus produced and then reaction of the resulting dibromides with disodium trithiocarbonate produced 2-hydroxymethyl- and 2-(diethoxymethyl)thieno[2,3-b]quinoxalines. Addition of bromine to some 6-substituted-2-(3,3-diethoxypropyn-1-yl)quinoxalines gave pyrrolo[1,2-a]quinoxalines. Treatment of a 3-(1,2-dibromoalkenyl)quinoline, a 3-(1,2-dibromoalkenyl)pyrazine, and a 5-(1,2-dibromoalkenyl)pyrimidine with disodium trithiocarbonate failed to induce thiophene ring formation.

A New Synthesis of 4,5,6,7-Tetrahydrothieno[3,2-c]pyridine

The title compounds was prepared via a sequence containing as the key step a thiophene ring formation from a 1,4-dicarbonyl intermediate

Thiophene ring formation during the interaction of alkylsulfenyl chlorides with esters of 3-methyl-1,2,4-pentatrienephosphonic acid

Dialkyl esters of 3-methyl-1,2,4-pentatrienephosphonic acid react with alkylsulfenyl chlorides to produce dialkyl esters of 2-thienylphosphonic acid.