Anhydro base of 4-(3-indolyl)pyrimidine

The reaction of 4-(3-indolyl)pyrimidine methiodide with alkali gives a stable anhydro base, which reacts under mild conditions with methyl iodide to give 1-methyl-4-(1-methyl-3-indolyl)pyrimidinium iodide. On the basis of the calculated molecular diagrams of both compounds it was concluded that they have high reactivities. The reaction of the anhydro base with an aqueous methanol solution of KOH, concentrated NH₄OH, hydrazine hydrate, and a mixture of malonic acid dinitrile with triethylamine leads to 3-acetylindole, 4-(3-indolyl)pyrimidine, 3(5)-(3-indolyl)pyrazole, and 2-amino-3-cyano-6-(3-indolyl)pyridine, respectively. 1-Methyl-4-(1-methyl-3-indolyl)pyrimidinium iodide under the same conditions gives similar compounds that contain a methyl group attached to the indole nitrogen atom. The structures of the synthesized compounds were confirmed by their IR, UV, PMR, and mass spectra.See [1] for our preliminary communication.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 212–218, February, 1982.     

Design of unusual captodative methylene substrates: 1-Alkyl-4(3)-(azolylmethyl)pyridinium salts 1

The unprecedented spontaneous oxidation of a carbon atom linked to captor (acceptor) and donor non-classical functional groups of several examples of 1-alkyl-4(3)-(1H-azolylmethyl) pyridinium salts 1 and 2 exemplifies a concomitant application of the arenoanalogy principle and the captodative effect in organic synthesis. A remarkably driving force by the nature of non-classical acceptor and donor heteroaromatic rings is observed upon the chemical behavior of the title compounds 1 and 2, modulating the susceptibility with which the methylene spacers oxidize to their oxomethyl counterparts 5 and 6. Access to dipolar 1-alkyl-3-pyridiniomethyl-3(5)-1,2,4-triazolate inner salts 4 was achieved.     

Recyclization of 2-(2-acylethyl)pyridinium salts

Recyclization of 2-(2-acylethyl)pyridinium salts on treatment with nucleophiles may occur in different ways, to give heterocyclic compounds of various classes, namely indoles (the Kost-Sagitullin reaction products), 4-aminoindoles, and 3-hydroxy-1,2,3,4-tetrahydroquinolines, the formation of which constitute novel reactions in the recyclization of pyridinium salts.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1217–1225, September, 1990.     

Reactions of N-(4-methoxybenzylidene)-N,N-dialkyliminium and 2-(4-methoxyphenyl)pyridinium salts with aliphatic amines

The reaction of 4-methoxybenzylideneiminium salts with methylamine and dimethylamine on heating results in replacement of the MeO group by an alkylamino-group, whereas the reaction with piperidine affords 3,5-bis-(4-methoxybenzyl)pyridine. N-Methyl-2-(4-methoxyphenyl)pyridinium iodide on treatment with methylamine undergoes dealkylation to the arylpyridine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1226–1229, September, 1990.     

Kinetics of the hydroxylation of N-picryl-4-[4-(dimethylamino)styryl]pyridinium salts by molecular oxygen in acetonitrile

The reactions of N-picryl-4-[4-(dimethylamino)styryl]pyridinium salts with molecular oxygen in the presence of 4-[4-(dimethylamino)styryl]pyridine (DASP) in acetonitrile proceeds with the formation of DASP picrate. The reactions are first-order relative to the salt cation, molecular oxygen, and the catalyst (DASP). L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R, Lyuksemburg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 34, No. 5, pp. 286–289, September–October, 1998.     

Nucleophilic addition to 3-substituted pyridinium salts: expedient syntheses of (-)-L-733,061 and (-)-CP-99,994

[reaction: see text] The addition of nucleophiles to 3-substituted pyridinium salts prepared from N-methylbenzamide and various pyridines has been investigated. Good to excellent regioselectivities favoring the 2,3-disubstituted 1,2-dihydropyridines were observed. The resulting 1,2-dihydropyridines led to the corresponding 2,3-disubstituted pyridines upon treatment with Mn(OAc)3/NaIO4. This methodology was also successfully applied to the enantioselective syntheses of (-)-L-733,061 and (-)-CP-99,994, two members of a new class of highly potent, nonpeptide, Substance P antagonists.     

Recyclization of selenophenopyrylium salts in alkaline media

Hydroxy derivatives of benzoselenophene that contain a hydroxyl group in the benzene ring are formed by the action of aqueous alcoholic sodium hydroxide on selenophenopyrylium perchlorates. The structure of the synthesized compounds was proved by IR and NMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1342–1344, October, 1973.     

The addition of alkylzinc iodides to 1-(phenoxycarbonyl)pyridinium salts

Several 1-(phenoxycarbonyl)-1,2-dihydropyridines were prepared by the addition of alkylzinc iodides to 1-(phenoxycarbonyl)pyridinium salts.     

Synthetic studies in the alkaloid field—IV: The sodium dithionite reduction of 1-[2-(3-indolyl)-ethyl]-3-methoxycarbonyl pyridinium bromides

The preparation of racemic indolo[2,3-a]quinolizine derivatives by sodium dithionite reduction of appropriate pyridinium bromides has been studied, A method has been found of influencing with high degree of stereoselectivity the C(12b)-C(2) stereochemical relationship in the products formed. The determination of the stereochemistry of the products by comparative examination of their ¹³C NMR spectra is described. The convenience of the sodium dithionite reduction method for the preparation of vallesiachotamine 1 models is discussed.     

Improved preparation of alkyl 2-(3-indolyl)-3-nitroalkanoates under fully heterogeneous conditions: stereoselective synthesis of alkyl (E)-2-(3-indolyl)-2-alkenoates

Ethyl 3-nitro-2-alkenoates can be generated starting from nitroalkanes and ethyl 2-oxoacetate under heterogeneous conditions that minimize work-up procedures, avoid any purification step and direct manipulation of the nitroalkene system. Reaction of ethyl 3-nitro-2-alkenoates, formed in situ from their acetoxy precursors, with indoles in the presence of basic alumina affords ethyl 2-(3-indolyl)-3-nitroalkanoates that are central intermediates for the preparation of tryptamines and carboline alkaloids. A base promoted elimination of nitrous acid from these nitroindolyl derivatives readily produces ethyl 2-(3-indolyl)-2-alkenoates with high E stereoselectivity. The latter compounds can be used as Michael acceptors in intra- and intermolecular reactions with nucleophilic reagents.     

1-Phthalimido-4-(3-indolyl)-2-siloxy-1,3-butadienes: synthesis and Diels-Alder reactivity

New 1-phthalimido-4-(3-indolyl)-2-trialkylsiloxy-1,3-butadienes were easily prepared from 1,3-dichloropropanone and their configurations were established from NMR data. Their Diels-Alder reactivity with different maleimides and quinones was studied, high yields of the exo cycloadducts being obtained, as confirmed by X-ray diffraction studies.     

Synthesis of 4-[3-(1H)-indolyl]-2-[N-guanidinomethyl]thiazole dihydrochloride

The title compound 3b was synthesized in three steps from acetaminothioacetamide ( 4b ) in 15% overall yield. This represents the first synthesis of a 2-guanidinomethylthiazole, which is a homolog of an important pharmacophore, 2-guanidinothiazole.     

Electrochemical reduction of N-(2-nitro-4-R-phenyl)pyridinium salts using redox-mediators

Electrochemical reduction of N-(2-nitroaryl)pyridinium chlorides was accomplished in acidic aqueous alcoholic medium in the galvanostatic mode using tin, titanium, vanadium, and iron chlorides as redox-mediators. The use of SnCl₂ as a mediator catalyst made it possible to shorten the electrosynthesis time as compared to the direct electroreduction on an electrode and prepare the intramolecular cyclization products, viz., substituted pyrido[1,2-a]benzimidazoles, in high yield. The influence of the mediator nature and its amount, current density, temperature, cathode material, medium acidity, and the substrate structure on the efficiency of reductive heterocyclization of N-(2-nitroaryl)pyridinium salts was studied.