Nucleophilic substitution of 4-bromomethyltriazolium with different nucleophiles

1,2,3-Triazolium salts draw much attentions in recent years. We developed a new synthetic method to heteroatom-functionalized triazoliums via nucleophilic substitution of 4-bromomethyltriazolium. This method afforded triazoliums with different S, N, and O heteroatom-substituents. Moreover, S_N2′ reaction was observed with alcohols or hydroxides. In addition, debromination and debromomethylation reaction occurred in some cases.     

Nucleophilic substitution reactions in 4-halonitro-pyrazolecarboxylic acids

The reaction of 4-bromo-1-methyl-3-nitropyrazole-5- and 4-bromo-1-methyl-5-nitro-pyrazole-3-carboxylic acids with arylamines in aqueous solution in the presence of monovalent copper salts leads to the formation of 4-arylamino- and 4-hydroxy substituted nitropyrazolecarboxylic acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 328–330, March, 1986.     

Stereoselective synthesis of vinylic chalcogenides through vinylic substitution by lithium organylchalcogenolates

Enol phosphates and enol tosilates of β-dicarbonyl compounds react with lithium organoselenolates to give β-organoseleno (Z)-α,β-unsaturated carbonyl compounds. Tetrasubstituted vinylic vic-bis(organylchalcogenides) of (E)-geometry have been prepared by this method.     

Nucleophilic substitution by a hydroxide ion at a vinylic carbon: ab initio and density functional theory studies on methoxyethene, 3-methoxypropenal, 2,3-dihydro-4H-pyran-4-one, and 4H-pyran-4-one.

Nucleophilic substitutions by a hydroxide ion at vinylic carbons of methoxyethene (system A), 3-methoxypropenal (system B), 2,3-dihydro-4H-pyran-4-one (system C), and 4H-pyran-4-one (system D) were calculated by Becke's three-parameter hybrid density functional-HF method with the Lee-Yang-Parr correlation functional (B3LYP//B3LYP) and the second-order M?ller-Plesset theory (MP2//B3LYP) using the 6-31+G(d) and AUG-cc-pVTZ basis sets. In addition, bulk solvent effects (aqueous solution) were estimated by the polarized continuum (overlapping spheres) model (PCM-B3LYP//B3LYP) and the polarizable conductor PCM model (CosmoPCM-B3LYP//B3LYP). The mechanisms as well as the influence of resonance, cyclic strain, aromatic, and polar effects on the reactivity of the calculated systems were determined. In the gas phase the rate-determining step of nucleophilic vinylic substitutions by a hydroxide ion may be either addition of hydroxide ion at the vinylic carbon (systems A and B) or elimination of the leaving group (systems C and D). In aqueous solution, for all four systems investigated, addition of hydroxide ion at the vinylic carbon is rate determining.     

Nucleophilic aromatic substitution with the anion of 3,5-disubstituted isoxazole-4-carboxylic acids

The preparation of the anion of a series of protected 3,5-disubstituted 4-isoxazolecarboxylic acids and the resulting addition of the anion to 9-chloroacridine is described. The addition-elimination reaction proceeds to give the expected acridinylmethylisoxazoles and has been justified based on calculated molecular mechanics energies and solvent effects.     

Nucleophilic substitution of 1,2,4-triazines

The reaction of 3-(methylthio)-5-carbethoxy-1,2,4-triazine (5) with ammonia was found to yield products from not only ammonia but also methanethiolate displacements. An account of the transformations and the products observed is given. The 3-position of 3,6-bis(methylthio)-5-carbamoyl-1,2,4-triazine (7) was shown to be more reactive than the 6-position toward nucleophilic substitution. Reduction at the 4,5 positions of triazine 5 occurred upon treatment with methanethiol under basic and neutral conditions.     

Nucleophilic substitution,demethylation and methylation in heterocyclic series

The products resulting from the condensation of potassium sulphanilamide and 3-methoxy-6-benzylsulphonylpyridazine have been investigated. In a reaction mixture consisting of N¹-methyl-sulphanilamide, N¹,N¹-dimethylsulphanilamide, 6-benzylsulphonyl-3-pyridazinone (VI) and 3-sulphanilamido-6-benzylsulphonylpyridazine (VII), demethylation, methylation and nucleophilic substitution takes place. The synthesis of VI and VII accomplished by an alternative route confirmed their structures.     

Nucleophilic substitution of halogen in 4-halo derivatives of glutamic acid

Reactions of diastereomeric dialkyl N-phthaloyl-4-haloglutamates withpara-anisidine were studied at high pressure, and an additional confirmation of the exactS _N2 mechanism of the reactions was obtained. Quantitative parameters of the relative reactivity of the diastereomers were found in various solvents, which made it possible to perform the desired synthesis of products of diastereomeric substitution. kg]Key words kw]glutamic acid kw]diastereoselectivity kw]nucleophilic substitution kw]reaction rate constant kw]high pressure.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 583–585, March, 1996.     

Nucleophilic substitution of hydrogen in the reaction of 1,2,4-triazin-4-oxides with cyanamide

It was shown that cyanamide can successfully be used in reactions of nucleophilic substitution of hydrogen with 1,2,4-triazin-4-oxides in the presence of a base to give 5-cyanoimino-1,2,4-triazines. It was found by¹³C NMR spectroscopy that these compounds and their alkylation products at the cyclic nitrogen atom exist in the form of 5-cyanoimino-2,5-dihydro-1,2,4-triazines. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1128–1130, June, 2000.     

The effects of vinylic and allylic fluorine substitution in iso-butylene

Molecular orbital calculations using the 3-21G basis set have been performed for iso-butylene (IB; 2-methyl-1-propene), difluoro-iso-butylene (DFIB; 1,1-difluoro-2-methyl-1-propene), hexafluoro-iso-butylene (HFIB; 3,3,3-trifluoro-2-(trifluoromethyl)-1-propene), and perfluoro-iso-butylene (PFIB; 1,1,3,3,3-pentafluoro-2-(trifluoromethyl)-1-propene). The effects of fluorine substitution were studied by comparison of several calculated quantities of the fluorinated compounds with those of IB. Through an analysis of the computed electron density distributions, it is suggested that a vinylic fluorine acts as a π acceptor, by electron transfer into the C? F bond, and a π repeller, by polarization of the adjacent π electrons. An allylic fluorine acts as a π attractor through electrostatic effects, although in HFIB a minor contribution from hyperconjugation was evident. Finally, electrostatic potentials for the molecules were calculated. These show that fluorine substitution has large effects on the electrostatic potential associated with the π electrons. These effects change the sign of the calculated electrostatic potential in the plane containing the π bond to such an extent that PFIB is quite susceptible to nucleophilic attack.     

Pyrroloquinolines and pyrroloisoquinolines. 4. Nucleophilic substitution in the pyrroloisoquinoline series

The reactivity of 1H-pyrrolo[2,3-f]isoquinoline with respect to nucleophilic substitution was studied in the case of the Chichibabin reaction and related transformations.See [1] for communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 495–497, April, 1984.     

Nucleophilic substitution and ring closure reactions of 4-chloro-3-nitro-2-quinolones

4-Chloro-3-nitro-2-quinolones 3 obtained from the 4-hydroxy quinolones 1 by nitration and chlorination, reacted with sodium azide to the 4-azido derivatives 4 which cyclized on thermolysis to yield the furoxanes 5 . Nucleophilic substitution reactions of 3 led to the 4-amino-, 4-fluoro- and 4-alkoxy-3-nitroquinolones 7, 8 and 9 , respectively. With thiols either 4-thio-3-nitro- 10 or 3,4-dithioquinolones 11 were obtained depending on the basic catalyst.     

Nucleophilic substitution reactions of pyranose polytosylates

The 2,3,4-tri-toluenesulfonate ester derivatives of the methyl pyranosides of l-arabinose, d-ribose, d-lyxose, and d-xylose have been prepared, and their substitution reactions with various nucleophiles have been examined. For arabinose, xylose, and ribose, highly regioselective monosubstitutions were observed with benzoate, nitrite, and azide anions. These reactions have led to short and simple routes from d-xylose to l-arabinose derivatives, from l-arabinose to d-xylose derivatives, and from d-ribose to l-lyxose derivatives. The tritosylate derived from methyl alpha-d-lyxopyranoside was unreactive toward nucleophilic substitution reactions, giving instead a dihydropyran product arising from an initial E2 elimination reaction of the 2-tosylate.     

Nucleophilic substitution inO-phenyldibenzofuranium and 10-phenylxanthonium cations

Reactions ofO-phenyldibenzofuranium tetrafluoroborate with nucleophiles (OH^?, NO₂ ^?, AcO^?) in aqueous media follow the S_NAr-mechanism and involve dehydroarenes. In DMSO, this salt smoothly reacts with NO₂ ^? and I^? with predominant opening of the furan ring. 10-Phenylxanthonium tetrafluoroborate readily arylates the NO₂ ^? ion in water (at the N and O atoms), mainly with predominant opening of the central ring, and is completely decomposed even with weak bases (NH₂OH, 2,4-dinitrophenylhydrazine). The Bayer—Villiger oxidation of this salt affords xanthone and 2-phenoxybenzoic acid.     

Nucleophilic substitution of halogen in 4-halo genated derivatives of glutamic acid

The reaction of nucleophilic substitution of bromine byp-anisidine in dimethyl (2S,4S)-and (2S,4R)-N-phthaloyl-4-bromoglutamates proceeds according to the S_N2 mechanism. The relative reactivity of diastereomers in various solvents was studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 652–655, April, 1995.The authors thank M. L. Gal'perin for assistance in designing the computer program for the calculations of the kinetic parameters.     

Nucleophilic substitution or dipolar 1,3-cycloaddition in reactions of cyanamide with 4-arylpyrimidine 1-oxides

Pyrimidine 1-oxides with cyanamide afforded 2-ureidopyrimidines as the result of the nucleophilic substitution of hydrogen, whereas the formation of similar 2-trichloroacetylaminopyrimidines occurs as dipolar 1,3-cycloaddition of the same oxides to trichloroacetonitrile under much more drastic conditions and in lower yields.