Mechanism of the second sulfenylation of indole

Sulfenylation of indole using a sulfenyl chloride occurs initially at the 3-position of the ring, leading to a 3-indolyl sulfide. When an excess of sulfenyl chloride is used, a second sulfide group is introduced at the 2-position, and an indolyl 2,3-bis-sulfide results. We have demonstrated that this second sulfenylation occurs not by direct introduction of the second sulfide at the 2-position but via initial formation of an indolenium 3,3-bis-sulfide intermediate, followed by migration of one of the sulfide groups to the 2-position. This was achieved by the isolation of two examples of 3H-indole 3,3-bis-sulfides and by subsequent demonstration that they rearrange to the indolyl 2,3-bis-sulfides by treatment with sulfenyl halides.     

Indole derivatives

2-(1-Octen-1-yl)indole was obtained by the Wittig reaction, and the product was used to prepare ethyl 7-[2-(1-octen-1-yl)-3-indolyl]-7-ketoheptanoate and the acid itself, which are possible model compounds in the synthesis of indole analogs of prostaglandins.     

Indole derivatives

A method for the introduction of a 3-indolyl group in compounds with an active methylene group was developed. The corresponding 3-indolyl diketones were obtained by condensation of 1-acetyl-3-indolinone with dimedone, 4-hydroxycoumarin, 1,2-diphenyl-3,5-pyrazolinedione, and barbituric and thiobarbituric acids and subsequent alkaline hydrolysis of the condensation products. The existence of cyclic six-membered 3-indolyl diketones in the enol form and of cyclic five-membered 3-indoly diketones in the keto form was shown by IR and UV spectroscopy. Depending on the conditions, (1-acetyl-3-indolyl)cyanoacetamide, 1,3-bis(1-acetyl-3-indolyl)-1,3,3-tricyano-2-amino-1-propene, and 1-acetyl-3-indolylmalononitrile are obtained in the condensation of 1-acetyl-3-indolinone with malononitrile. 1-Acetyl-3-indolylmalononitrile exists in equilibrium with the keteneimine form and in protic solvents is converted to 3-cyano-8-acetylpyrrolo[2,3-b]indole by intramolecular cyclization.See [1] for communication CX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 360–368, March, 1977.     

Simple route to 3-(2-indolyl)-1-propanones via a furan recyclization reaction

A simple route to 1-R-3-(2-indolyl)-1-propanones has been elaborated based on recyclization of 2-(2-aminobenzyl)furan derivatives. Being a modification of the Reissert indole synthesis, our approach employs the furan ring as a source of carbonyl function. This approach is general and allows varying of substituents in aromatic ring as well as in 3-position of indole nucleus.     

Indole derivatives

The Claisen condensation of methyl 3-indolylacetate with dimethyl carbonate, methyl benzoate, methyl formate, and methyl acetate proceeds with acylation of the CH₂ group. Only the carbomethoxy group attached to the nitrogen atom of the indole ring is retained. The corresponding 5-(3-indolyl)pyrimidines were obtained by condensation of thiourea and acetamidine with the products of acylation of methyl 3-indolylacetate with methyl formate and methyl acetate.See [1] for Communication 118.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 55–58, January, 1980.     

Indole derivatives. 120. Synthesis of higher ω-(3-indolyl)alkanoic acids by alkylation of indole lactones

The alkylation of indole with the tridecanolide, pentadecanolide, and oxo lactones of ω-hydroxyethoxyundecanoic and ω-hydroxybutoxyundecanoic acids was investigated. Higher indolylalkanoic acids, viz., ω-(3-indolyl)undecanoic, ω-(3-indolyl)tride-canoic, and ω-(3-indolyl)pentadecanoic acids, were obtained. The scheme of the alkylation of indole with oxo lactones, and the difference in the rates of the reactions of the ester and lactone bonds, were established from the reaction products. See [1] for communication 119. Translated from Khimiya Getetotsiklicheskikh Soedinenii, No. 2, pp. 216–217, February, 1980.     

Umpolung Reactivity of Indole through Gold Catalysis

Electrophilic indole? Indoles, which are typically nucleophilic, can be made electrophilic through gold catalysis. By using an ortho-azido group to deliver a nitrene intramolecularly, an arylalkyne is converted into a gold carbene intermediate containing an indole skeleton that is highly electrophilic at the 3-position. A range of functionalized indoles is readily accessed by utilizing this strategy.     

Indole derivatives

Curtius rearrangement of azides of 3-indolylalkanoic acids gave 3-indolyl isocyanates, which were converted to ureas by the action of ammonia and amines. Urethanes were obtained by alcoholysis of 3-indolyl isocyanate, and 1-(3-indolyl)-2-azetidinone was obtained by reaction with diazomethane. Hydrolysis of 3-indolyl isocyanate and hydrogenolysis of its benzylurethane gave 3-aminoindole hydrochloride, which was characterized by synthesis of the monoacetyl derivative.     

The oxidative coupling of indole with some phenolic compounds,naphthols and catechols

The oxidative coupling of indole with three naphthols, 2-naphthol, 2,3-dihydroxynaphthalene and 2,7-dihydroxynaphthalene gave 1,1-bis(3′-indolyl)-2(1H)naphthalenone, 1,1-bis(3′-indolyl)-3-hydroxy-2(1H)naphthalenone and 1,1-bis(3′-indolyl)-7-hydroxy-2(1H)naphthalenone, respectively. The coupling of indole with protocatechuic aldehyde gave bis-(3-indolyl)-(3′,4′-di-hydroxyphenyl)methane and that of indole with homocatechol gave 3-(2′-methyl-3′,4′-di-hydroxyphenyl)indole.     

Indole derivatives CXV. Synthesis and some transformations of 5-(3-indolyl)isoxazole-3-carboxylic acid

5-(3-Indolyl)isoxazole-3-carboxylic acid and its amide and hydrazide were obtained from ethyl 5-(3-indolyl)isoxazole-3-carboxylate. When 5-(3-indolyl)isoxazole-3-carboxylate is heated, it undergoes decarboxylation with isomerization to 3-(-cyanoacetyl)indole; when it is heated in alcohol with hydrazine and phenylhydrazine in the presence of copper, it undergoes isomerization to 5-(3-indolyl)pyrazole-3-carboxylic and 1-phenyl-5-(3-indolyl)-pyrazole-3-carboxylic acids. 5-(3-Indolyl)pyrazole-3-carboxylic acid hydrazide is formed when a solution of ethyl 5-(3-indolyl)isoxazole-3-carboxylate is refluxed with hydrazine in 96% alcohol.See [1] for communication CXIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 936–938, July, 1978.     

Reactions of Indole and Its Derivatives with Cotarnine. Rearrangement of 5-(1-Indolyl)-4-methoxy-6-methyl- 5,6,7,8-tetrahydro[1,3]dioxolo[4,5-g]isoquinolines

A synthetic route to compounds of the indolyltetrahydroisoquinoline series was developed on the basis of the reaction of cotarnine with indole derivatives. Aminoalkylation of indole and its derivatives with cotarnine occurs regioselectively at the nitrogen atom of the indole fragment to give the corresponding 5-(1-indolyl)-4-methoxy-6-methyl-5,6,7,8-tetrahydro[1,3]dioxolo[4,5-g]isoquinolines. The products were found to undergo rearrangement into isomeric 5-(3-indolyl)-4-methoxy-6-methyl-5,6,7,8-tetrahydro[1,3]dioxolo[4,5-g]isoquinolines which constitute a new class of indolyltetrahydroisoquinoline systems.     

Synthesis of novel 1-phenyl-1H-indole-2-carboxylic acids. II. Preparation of 3-dialkylamino, 3-alkylthio, 3-alkylsulfinyl,and 3-alkylsulfonyl derivatives

The synthesis of novel indole-2-carboxylic acids with amino- and sulfur-containing substituents in the indole 3-position is described. An Ullmann reaction with bromobenzene converted 1H-indoles with 3-(acetylamino)- and 3-(diethylamino)-substituents into 1-phenyl-1H-indoles. Reaction of 3-unsubstituted indoles with thionyl chloride provided indole 3-sulfinyl chlorides, which reacted with alkyl and aryl Grignard reagents to form the corresponding sulfoxides. The indole sulfoxides thus obtained were reduced to sulfides or oxidized to sulfones.     

Indole derivatives

1-Carbomethoxy-3-indolylcyanoacetic ester reacts with amidines, guanidine, and thiourea to give, respectively, 2-alkyl- and 2-aryl-5-(3-indolyl)-4-amino-6-hydroxypyrimidines and 2-amino- and 2-thio-5-(3-indolyl)-4-amino-6-hydroxypyrimidines.See [1] for communication CVIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1513–1515, November, 1976.     

Copper-catalyzed sulfenylation of pyrroles with disulfides or thiols: directly synthesis of sulfenyl pyrroles

We present here the synthesis of sulfenyl pyrroles by copper-catalyzed sulfenylation of pyrroles with organic disulfides or thiols. The direct sulfenylation of pyrroles with organic disulfides has been accomplished in the presence of 3 mol % of CuI in DMSO at 110 °C under air atmosphere. In the other hand, sulfenylation of pyrroles with thiols were performed in the same solvent and temperature, however it is necessary 5 mol % of CuI and nitrogen atmosphere. Using these protocols we were able to produce 2-sulfenyl pyrroles in good to excellent yields and with high selectivity without use of any ligand or additive.     

Indole derivatives

Salts of 2-nitro-1-(3-indolyl)ethanesulfonic acid were obtained by the reaction of nitrovinylindole with potassium and sodium bisulfites. The salts were converted to the p-toluidine salt, which was reduced to 2-amino-1-(3-indolyl)ethanesulfonic acid (3-indolyl-taurine).See [1] for communication LXII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 205–207, February, 1971.     

The reaction of N-Acylpyridinium salts with indole

Depending on the solvent used and the ratio of the reactants, N-acylpyridinium salts condense with indole to give 3-(N-acyl-1,4-dihydro-4-pyridyl)indole ( 1 ) or 4-(N-acyl-3-indolyl)pyridinium chloride ( 3 ). Compound 1 is an intermediate in the formation of compound 3 . The reaction mechanism has been studied, and a hydrogen transfer reaction is suggested as a key step. Alkaline hydrolysis, e.g., of 4-(N-acetyl-3-indolyl)pyridinium chloride ( 3a ), gave 3-(4-pyridyl)indole ( 2a ). The reaction of α-chlorosubstituted acyl halides with indole, in the presence of pyridine constitutes a convenient synthesis of 3-chloroacylindoles.     

Indole derivatives

The Fischer condensation of arylhydrazones of 2, 2, 5, 5-tetramethyl-pyrrolid-3-one has given 1, 1, 3, 3-tetramethyl-7, 8-benzo-1, 2, 3, 4-tetrahydropyrrolo[3, 4-b]indole and 1, 1, 3, 3, 7-pentamethyl-1, 2, 3, 4-tetrahydropyrrolo[3, 4-b]indole. On Clemmensen reduction of the latter, the pyrrole ring undergoes degradation.     

Indole derivatives

The Fischer condensation of arylhydrazones of 2, 2, 5, 5-tetramethyl-pyrrolid-3-one has given 1, 1, 3, 3-tetramethyl-7, 8-benzo-1, 2, 3, 4-tetrahydropyrrolo[3, 4-b]indole and 1, 1, 3, 3, 7-pentamethyl-1, 2, 3, 4-tetrahydropyrrolo[3, 4-b]indole. On Clemmensen reduction of the latter, the pyrrole ring undergoes degradation.For Part XXIX, see [1].     

Indole derivatives. 127. Investigation of the alkylation of indole by polyesters

The alkylation of indole by polyesters of -hydroxyalkanoic acids was studied. The optimum conditions and ratios of the reacting substances were found, and a number of -(3-indolyl)alkanoic acids were obtained.See [1] for communication 126.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 519–521, April, 1985.     

Indole derivatives

A method is described for the preparation of -(3-indolyl)acrolein. Oximation of this followed by dehydration gives -(3-indolyl)acrylonitrile. Reduction gives -(3-indolyl)allyl alcohol.For part XXXII, see [1].