Nucleophilic substitution of chlorine atoms in polyvinyl chloride

To modify properties of polyvinyl chloride, its chlorine atoms were substituted using sodium salts of pyrazole, 3,5-dimethylpyrazole, and 2-mercaptobenzimidazole.     

Reaction of lower dialkylhydrazones of acrolein with hydrazine and methylhydrazine

Papers on the synthesis of dialkylhydrazones of , -unsaturated aldehydes have appeared comparatively recently ¦1, 2¦. Hitherto the chemical properties of these compounds have not been studied very much.     

Nucleophilic substitution in nitrofluorenones

The reaction of 2,4,5,7-tetranitrofluorenone with amines, thiols, and phenol in a polar aprotic solvent led to the preferable substitution of the nitro group in the position 2, and in the reaction of 2,4,7-trinitrofluorenone first the nitro group in the position 4 was replaced. The different regioselectivity is due evidently to the steric hindrances to the nucleophilic attack on the atom C⁴ caused by the nitro group in the position 5 of tetranitrofluorenone.     

Nucleophilic substitution in hydroxyisoxazolidines

Nucleophilic substitution of the hydroxy-group in 3- (or 5-)hydroxyisoxazolidines affords the aryl(alkyl)amino-, alkoxy-, and hydrazino-compounds. 5-Dimethylhydrazinooxazolidines exist preferentially in the linear form.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1661–1665, December, 1988.     

Five-to-six membered ring-rearrangements in the reaction of 5-perfluoroalkyl-1,2,4-oxadiazoles with hydrazine and methylhydrazine

The hydrazinolysis reaction of 5-perfluoroalkyl-1,2,4-oxadiazoles with hydrazine or methylhydrazine as bidentate nucleophiles has been investigated. The reaction occurred through the addition of the bidentate nucleophile to the C(5)-N(4) double bond of the 1,2,4-oxadiazole followed by ring-opening and ring-closure (ANRORC) involving the second nucleophilic site of the reagent. This ring-closure step could involve either the original C(3) of the 1,2,4-oxadiazole (giving a five-to-five membered ring rearrangement) or an additional electrophilic center linked to it (exploiting a five-to-six membered ring rearrangement). An alternative initial nucleophilic attack may involve the additional electrophilic center linked at C(3), that is the carbonyl group, leading to the formation of the hydrazones which undergo the Boulton-Katritzky rearrangement (BKR). The chosen reaction path is a function of the used nucleophile and of the nature of the substituent at C(3). At variance with previous hypotheses, when methylhydrazine was used, the observed regiochemistry always showed the preferred initial attack by the less hindered NH(2) end of the nucleophile on C(5). Moreover, new spectroscopic evidence allowed the assignment of correct structures to the products formed by reaction of 5-perfluoroalkyl-3-phenyl-1,2,4-oxadiazoles with methylhydrazine.     

Nucleophilic substitution in ethyl fluorosulfonoxydifluoroacetate

Conclusions Ethyl fluorosulfonoxydifluoroacetate undergoes nucleophilic replacement with the formation of derivatives of difluoroacetic acid. The reaction with fluoride anion mainly features cleavage of the S-O bond leading to the acid fluoride of the monoethyl ester of oxalic acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1435–1437, June, 1985.     

Nucleophilic substitution in 1,2,3-thiadiazoles

By reactions of nucleophilic substitution of the halogen atom in 5-halo-1,2,3-thiadiazoles (IV), we have obtained 5-amino- (I, V), hydrazino-(VI, VII, IX, X), and mercapto- (VIII) 1, 2, 3-thiadiazoles. We show that upon reaction with amines, a mixture of 5-amino-1, 2, 3-thiadiazoles (I) and 5-mercapto-1, 2, 3-triazoles (II) is formed, and also the reaction product of compounds I and IV,: the selectivity of this process depends only on the type of solvent.Organic Synthesis Technology Department, Urals State Technical University—UPI, Ekaterinburg 620002. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 554–559, April, 1994. Original article submitted February 28, 1994.     

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 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 in the azine series

This review is devoted to a discussion of the quantitative characteristics of the reactivities and mechanisms of the reactions of substituted azines with nucleophilic reagents.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 723–734, June, 1973.     

Nucleophilic substitution in iodonium derivatives of indole

3-Indolylphenyliodonium tosylate and trifluoroacetate were synthesized, and their reaction with halide anions was investigated. It is shown that the iodonium grouping is replaced by halogen in all cases. 3-Fluoroindole was synthesized for the first time. The mechanism of the reaction is discussed, and data from the mass spectra of the 3-haloindoles obtained are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 933–935, July, 1978.     

Nucleophilic substitution of bromine in vicinal bromotrifluoroalkylamines

SecondaryN-(2-bromo-3,3,3-trifluoropropyl)-N-alkylamines cyclize under the action of bases to yield aziridines. TertiaryN-(2-bromo-3,3,3-trifluoropropyl)amines react with S-nucleophiles to give products of bromine substitution.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 955–957, May, 1994.     

Nucleophilic substitution reactions of aryl dithioacetates with pyridines in acetonitrile

Kinetic studies of the pyridinolysis (XC(5)H(4)N) of aryl dithioacetates (CH(3)C(=S)SC(6)H(4)Z) are carried out in acetonitrile at 60.0 degrees C. A biphasic Br?nsted plot is obtained with a change in slope from a large value (beta(X) congruent with 0.9) to a small value (beta(X) congruent with 0.4) at pK(a) degrees = 5.2, which is attributed to a change in the rate-limiting step from breakdown to formation of a zwitterionic tetrahedral intermediate, T(+/-), in the reaction path as the basicity of the pyridine nucleophile increases. A clear-cut change in the cross-interaction constants rho(XZ) from a large positive value (rho(XZ) = +1.34) to a small negative value (rho(XZ) = -0.15) supports the mechanistic change proposed.     

Nucleophilic substitution reactions of alpha-chloroacetanilides with benzylamines in dimethyl sulfoxide

Kinetic studies of the reactions of alpha-chloroacetanilides (YC6H4NRC(=O)CH2Cl; R = H (5) and CH3 (6)) with benzylamines (NH2CH2C6H4X) were carried out in dimethyl sulfoxide at 55.0 degrees C. The Br?nsted betaX values were in the range from 0.6 to 0.9 and cross-interaction constants phoXY were positive: phoXY = +0.21 and +0.18 for 5 and 6, respectively. The rates were faster with 6 than with 5 and inverse secondary kinetic isotope effects involving deuterated benzylamine (ND2CH2C6H4X) nucleophiles, kH/kD < 1.0, were obtained. Based on these and other results, a stepwise mechanism with rate-limiting expulsion of the chloride leaving group from a zwitterionic tetrahedral intermediate, T+/-, is proposed. In this mechanism, a prior carbonyl addition to T+/- is followed by a bridged type transition state to expel the chloride. An enolate-like transition state in which the developing negative charge on C(alpha) delocalizes toward the carbonyl group (nC-->pi*(C=O) interaction) is not feasible for the present series of reactions due to a stronger charge transfer involving the lone pair on the anilino nitrogen (nAN-->pi*(C=O) interaction).     

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.