Unprecedented Multicomponent Reaction of Indoles,CS2 and Nitroarenes: Stereoselective Synthesis of (Z)-3-((Arylamino)methylene)indoline-2-thiones

An efficient method for the stereoselective synthesis of (Z)-3-((arylamino)methylene)indoline-2-thiones have been developed via a novel multicomponent reaction of indoles, CS₂ and nitroarenes. A range of functionalized indoline-2-thiones were prepared in moderate to good yields from easily available starting materials. The indoline-2-thione products can be easily derivatized to give biologically active thieno[2,3-b]indole and thiopyrano[2,3-b]indole skeletons in high yields.     

BF3 etherate-mediated microwave-assisted facile synthesis of thiopyrano[2,3-b]indol-2-one

A facile synthesis of indole annulated 2H-thiopyran-2-ones has been developed by condensation of indoline-2-thiones with acetoacetic esters in the presence of borontrifluoride etherate (BF₃ etherate) using microwave irradiation. This one-step operationally simple methodology leads to thiopyrano[2,3-b]indol-2-ones in good yields.     

Synthesis of Indole Derivatives by [2 + 2] Photocycloaddition of Indoline-2-thiones with alkenes and photodesulfurization of indoline-2-thiones

The photochemical synthesis of indole derivatives starting from the indoline-2-thiones 1 is described. Irradiation of indoline-2-thiones 1 in the presence of alkenes 3 gave 2-alkyl-3H-indoles 4 – 7 or 2-alkylindoles 8 – 22 through the ring cleavage of the intermediates, spirocyclic amino-thietanes, initially derived by [2 + 2] cycloaddition of the C?S bond of 1 and the C?C bond of 3 . Irradiation of 1 in the presence of trialkylamines 26 gave desulfurization products 27 – 32 and unexpected 3-alkylindoles 33 – 40 . N-Acylindoline-2-thiones 11 - p yielded the deacylated products, indoline-2-thiones 1a - b , and ethyl esters 43 through γ-H abstraction by the excited thioamide S-atom when irradiated in CDC1₃/EtOH or benzene/EtOH. Oxygen analogues 2a - d also underwent intramolecular H abstraction to give the indolin-2-ones 2e – f and ethyl esters 43 in a similar way.     

A one-pot, three-component synthesis of thiazolidine-2-thiones

An efficient method for the synthesis of thiazolidine-2-thiones is described via regiospecific iodocyclization of an allyl amine, carbon disulfide, and iodine. Dehydrohalogenation of the iodo-derivatives gives thiazole-2(3H)-thiones. In addition, nucleophilic substitution of the iodine in the products is accomplished using NaN₃, thiophenol, or dithiocarbamate.     

Copper-catalyzed chalcogenoamination of 2-alkynylanilines with dichalcogenides for one-step synthesis of 3-sulfenylindoles and 3-selenylindoles

The copper-catalyzed chalcogenoamination of 2-alkynylanilines with dichalcogenides has been achieved under mild reaction conditions using the weak base Cs₂CO₃ in combination with air oxidant, providing a convenient and efficient method for synthesis of 3-sulfenylindoles and 3-selenylindoles, including complex products bearing two attached 3-sulfenylindole rings.     

Ultrasound-mediated efficient synthesis of dihydrothiopyrano[2,3-<Emphasis Type="Italic">b</Emphasis>]indole-3-carbonitrile derivatives

An efficient one-pot synthesis of fused dihydrothiopyrano[2,3-b]indole-3-carbonitriles has been developed through ultrasound mediated reaction by simply combining malononitrile and various aldehydes with two indoline-2(3H)-thiones. The method has the advantages of high yields, short reaction time, good functional group tolerance and green reaction conditions.     

Reduction of Indolin-2-ones and Desulfurization of Indoline-2-thiones to Indoline and Indole Derivatives

Reduction of indolin-2-ones with lithium aluminium hydride (LAH) or diisobutylaluminum hydride (DIBAL) and desulfurization of indoline-2-thiones with Raney-Ni were investigated. Treatment of indoline-2-ones 1 with LAH or DIBAL yield indoles 4 and/or indolines 3 in moderate-to high yield depending on the substituents at N and C(3) of 1 . Indoline-2-thiones 2 were desulfurized with Raney-Ni to give indoles 4 and/or indolines 3 .     

A new route to the versatile synthesis of thiopyrano[2,3-b:6,5-b′]diindoles via 2-(alkylthio)-indole-3-carbaldehydes

A versatile synthesis of symmetrically and unsymmetrically substituted thiopyrano[2,3-b:6,5-b′]diindoles has been developed by the condensation of 2-(alkylthio)-indole-3-carbaldehydes with indoline-2-thiones in the presence of catalytic amount of ethylenediamine diacetate (EDDA). The EDDA mediated condensation leads to a spontaneous cyclization followed by aromatization to form thiopyrano[2,3-b:6,5-b′]diindoles in quantitative yields.     

Interrupted Intramolecular Hydroaminomethylation of N-Protected-2-vinyl Anilines: Novel Access to 3-Substitued Indoles or Indoline-2-ols

A new synthetic alternative to the synthesis of 3-methyl indoles and 3-methyl indoline-2-ols with an excellent atomic economy is presented in this study. It is demonstrated that the intramolecular interrupted hydroaminomethylation (HAM) reaction is a powerful tool for the formation of these compounds, which exhibit wide-ranging biological activity. Several N-Protected-2-vinyl anilines were synthesized and involved in the reaction producing the corresponding 3-methylindole or 3-methyl indoline-2-ol depending on the nature of the N-protecting groups.     

Reduction of 4-hydroxy(alkoxy)hexahydropyrimidine-2-thiones and 1,2,3,6-tetrahydropyrimidine-2-thiones by the NaBH4-CF3COOH system. Synthesis of hexahydropyrimidine-2-thiones

A convenient method for the synthesis of hexahydropyrimidine-2-thiones by the reduction of the readily accessible 4-hydroxy(alkoxy)hexahydropyrimidine-2-thiones and 1,2,3,6-tetrahydropyrimidine-2-thiones by the NaBH₄-CF₃COOH system was proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1378–1388, October, 1993.     

Enantioselective synthesis of indolo[2,3-b]-dihydrothiopyranones via [3+3] cycloaddition of chiral α,β-unsaturated acylammonium salts

A nucleophile-catalyzed Michael addition/proton transfer/lactonization (NCMPL) organocascade process of chiral α,β-unsaturated acylammonium salts and indoline-2-thiones is described, which delivers the indolo[2,3-b]dihydrothiopyranone motifs in high yields (up to 97%) with good to excellent enantioselectivities (up to 98% ee).     

I2-catalyzed base-free cyclization of 3-homoallylquinoline-2-thiones: facile synthesis of tetracyclic,furothiopyrano[2,3-b]quinolines

I₂-catalyzed base-free reactions of 3-homoallylquinoline-2-thiones have been described for the synthesis of tetracyclic quinolines, tetrahydrofuro [2′,4′:4,6]thiopyrano[2,3-b]quinolines in excellent yields. Similarly, I₂-catalyzed reactions could proceed to tricyclic quinolines from hydroxyl group protected 3-homoallylquinoline-2-thiones. However, deprotection of group in tricyclic quinoline with HI again transformed into tetracyclic quinoline. The sulfonium salt intermediate has been proposed to explain these reactions.     

An expedient route to highly functionalized 2H-chromene-2-thiones via ring annulation of β-oxodithioesters catalyzed by InCl3 under solvent-free conditions

A convenient and one-pot synthesis of 3-aroyl/heteroaroyl-2H-chromene-2-thiones and benzo[f]2H-chromene-2-thiones has been developed by the condensation of β-oxodithioesters and salicylaldehydes/α-hydroxynaphthaldehydes in the presence of indium trichloride under solvent-free conditions. The reaction is operationally facile, readily scalable, and offers rapid entry into differentially substituted chromene-2-thione scaffolds.     

A Cs2CO3-mediated simple and selective method for the alkylation and acylation of 3,4-dihydropyrimidin-2(1H)-thiones

Alkyl and acyl derivatives of 3,4-dihydropyrimidin-2(1H)-thiones were synthesized in good to excellent yields in the presence of Cs₂CO₃, a mild base. The method evidences a selective S-alkylation when using acyl chlorides as efficient acylating agents at room temperature on the 2-thioxo-dihydropyrimidone moiety. A possible mechanistic interpretation of the different selectivities in case of alkylation and acylation was done with the help of a geometry optimization process.     

A simple entry to novel spiro dihydroquinoline-oxindoles using Povarov reaction between 3-N-aryliminoisatins and isoeugenol

An easy, fast, and cheap way for the synthesis of the new 4′-(4-hydroxy-3-methoxyphenyl)-3′-methyl-3′,4′-dihydro-1′H-spiro[indoline-3,2′-quinolin]-2-ones using BF₃ OEt₂-promoted imino Diels-Alder cycloaddition between ketimine-isatin derivatives and trans-isoeugenol.     

Selective reductive cleavage of 2-(phenylthio)pyrimidines for efficient synthesis of 2-(H)pyrimidines

A reaction method is described for selective reductive cleavage of 2-(phenylthio)pyrimidines using Pd(OAc)₂ and Et₃SiH to produce 2-(H)pyrimidines. The reaction proceeds efficiently with a wide range of 2-(phenylthio)pyrimidines. Considering the ready availability of 2-(arylthio)pyrimidines derived from oxidative CS cross coupling of 3,4-dihydropyrimidin-1H-2-thiones (DHPMs), this method unambiguously provides a shortcut to the preparation of 2-(H)pyrimidines with unprecedented diversity.     

Diastereoselective synthesis of 4,5-dihydroxyimidazolidin-2-ones (-thiones) and their structure

Studies on the synthesis of 4,5-dihydroxyimidazolidin-2-ones (-thiones) based on the condensation of ureas or thioureas with glyoxal or 1,2-dioxo-1,2-diphenylethane showed high diastereoselectivity in the formation of racemates (trans-diastereomers) of 4,5-dihydroxyimidazolidin-2-ones (-thiones) and meso-forms (cis-diastereomers) of 4,5-dihydroxy-4,5-diphenyl-1,3-dialkylimidazolidine-2-thiones; plausible mechanisms of their formation were suggested. X-ray diffraction studies confirmed structures of diastereomers for separate examples of racemates and meso-forms of 4,5-dihydroxyimidazolidin-2-ones (-thiones).     

Synthesis of annulated heterocyclic systems based on 4-CF3- or 4-CHF2-3-cyano-(1H)-pyridine-2-thiones

A simple and convenient preparative method for the synthesis of 3-cyano-4-difluoro- and -trifluoromethylpyridine-2(1H)-thiones was developed. During studies of synthetic potential of these compounds, approaches to the synthesis of a number of annulated heterocyclic systems were suggested.     

A novel multicomponent approach to the synthesis of 1,3-thiazolidine-2-thiones

An easy, efficient, and simple one-pot approach for the synthesis of 1,3-thiazolidine-2-thiones via multicomponent reaction is reported. The reaction of a primary amine with carbon disulfide in the presence of dibenzoylacetylene or bis(4-methyl-1-benzoyl)acetylene in a mixture of CH₂Cl₂ and H₂O after 5 h, afforded the title compound as alkene diastereomers.     

Three-component condensation of 3-aminothiophene derivatives with isatines and Meldrum’s acid. Synthesis of 2,5′-dioxo-3′-phenyl-5′,6′-dihydro-4′H-spiro[indoline-3,7′-thieno[3,2-b]pyridine]-2′-carboxylic acids

A method for the synthesis of 2,5′-dioxo-3′-phenyl-5′,6′-dihydro-4′H-spiro[indoline-3,7′-thieno[3,2-b]pyridine]-2′-carboxylic acids was elaborated based on the three-component condensation of 3-aminothiophenes, Meldrum’s acid, and isatines.