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Chaikovskii, V. K.; Skorokhodov, V. I.; Филимонов, В. Д.

doi:10.1023/a:1013435608182

Cited by 31 publications

(24 citation statements)

References 7 publications

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“…35 Dry solvents were dried by molecular sieves (3 or 4 Å) that activated in vacuo at 200°C and stored over molecular sieves. TLC was performed on Merck TLC plates silica gel 60 F 254 0.25 mm.…”

Section: Generalmentioning

confidence: 99%

Chemical approach for the syntheses of GM4 isomers with sialic acid to non-natural linkage positions on galactose

Kurimoto

Yamamura

Miyagawa

2015

Carbohydrate Research

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Section: Generalmentioning

confidence: 99%

Chemical approach for the syntheses of GM4 isomers with sialic acid to non-natural linkage positions on galactose

Kurimoto

Yamamura

Miyagawa

2015

Carbohydrate Research

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“…Tricycloheptane I [1], and also NIS [14], NCS [15], and cyanamide [16] were synthesized by published procedures; NBS of pure grade was recrystallized from dioxane before use.…”

Section: Methodsmentioning

confidence: 99%

Stereochemistry of conjugate halogenation of 1-phenyltricyclo[4.1.0.02,7]heptane

2004

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1-Phenyltricyclo[4.1.0.0 2,7 ]heptane reacts with N-bromo-and N-chlorosuccinimides in the presence of external nucleophiles providing products of a conjugate (electrophilic with respect to halogen) addition across the central bond C 1 C 7 of the bicyclo[3.1.1]heptane structure with a pronounces endo,anti-stereoselectivity. In similar reactions with N-iodosuccinimide the products obtained originated mainly from endo,syn-addition across the C 1 C 7 bond. The reasons for differences in the selectivity of the conjugate halogenation are discussed applying the data of the quantum-chemical calculation in the basis MP2/STO 3G of the electronic and spatial structure of the reaction intermediates, norpinanyl cations of benzyl type.1-Phenyltricyclo[4.1.0.0 2,7 ]heptane (I) was already subjected to study in ionic addition reactions initiated with an electrophilic halogen. It was shown in [1] that bromohydroxylation and bromomethoxylation of hydrocarbon I with the use of N-bromosuccinimide (NBS) occurred exclusively at the C 1 C 7 bond, and therewith the bromine cation attacked strictly the b-position with respect to the phenyl substituent from the endo-side with a pronounced anti-stereoselectivity (the ratio of endo,anti-and endo,syn-adducts was 13 : 1 and 15:1 respectively). The observed stereoselectivity was ascribed to the structural features of the intermediate norpinanyl cation of benzyl type IIa where the trimethylene fragment shielded the reaction center from the syn-side resulting in more favorable anti-attack of nucleophile. single product of endo,anti-addition [2]. However, elemental iodine added to hydrocarbon I in the endo,synstereoselective fashion (ratio of endo,anti-and endo,synadducts was 1:3). It was suggested that in the intermediate of this reaction, benzyl cation IIb, atom H 7 suffered repulsion from the bulky iodine and therefore approached the reaction site thus creating significant steric hindrancies to the nucleophile approach from the anti-side.Our recent investigations [3] demonstrated that NBS as well as N-chlorosuccinimide (NCS) in the absence of external nucleophiles in CH 2 Cl 2 solution added to tricycloheptane I across the central C 1 C 7 bond in keeping with Markownikoff rule to furnish a mixture of norpinane endo,anti-adducts corresponding to concurrent O-and N-alkylation of the succinyl moiety (ratio of the structural isomers was ~70:30 and 60:40 respectively). It was also established [3] that the chlorohydroxylation of hydrocarbon I effected by NCS in aqueous acetone occurred exclusively at the C 1 C 7 bond affording an only product of the conjugate endo,anti-addition with a norpinane structure. However the chloromethjoxylation with the use of NCS in methanol afforded a mixture of endo,anti-and endo,syn-adducts in a 49:1 ratio [4]. The numerous examples of conjugate iodination [5] as well as several instances of conjugate bromination [2, 6, 7] of unsubstituted tricyclo[4.1.0.0 2,7 ]heptane demonstrated+ ; 3K + ; + DQWL ,,D B H , , , E V\Q Later the other reactions initiated with electrophi...

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“…However compounds 1a-d, as a result of deactivation of the heterocyclic nucleus by the electron-withdrawing fluorinated group, were not iodinated under these conditions. To intruduce an iodine atom into the molecule of compounds 1b-d we used N-iodosuccinimide in sulfuric acid, which has been used for the iodination of aromatic compounds [16]. As a result the 4-iodo derivatives 5b-d were obtained in high yield.…”

mentioning

confidence: 99%

Chemical properties of derivatives of N-difluoromethyl-and N-2-H-tetrafluoroethylpyrazoles

Petko

Sokolenko

Yagupol’skii

2006

Chem Heterocycl Compd

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Nitration, chlorination, bromination, and iodination reactions have been investigated for pyrazole derivatives containing a difluoromethylene fragment directly on a nitrogen atom. Conditions have been found for introducing a cyano group into the nucleus of N-2-H-tetrafluoroethylpyrazole and converting it into carboxyl or tetrazole functions.Pyrazole derivatives enter into the composition of many compounds possessing high biological activity. Several of them, containing fluorinated groupings, are used as medicinal preparations [1] and pesticides [2].Compounds containing a difluoromethylene fragment linked directly with the nitrogen atom have been little studied up to the present. Trialkylamines containing the α-difluoromethylene fragment are hydrolytically unstable [3-5] as a result of the electron-donating influence of the unshared electron pair of nitrogen. However in the case of nitrogen heterocycles such compounds are significantly more stable, since the nitrogen electron pair is involved in the π−conjugation of the heterocyclic ring. Difluoromethyl and 2H-tetrafluoroethyl derivatives of pyrrole [5], imidazole, benzimidazole [6-8], triazole, 3,5-dimethyl-, and 3-carbethoxypyrazole [9, 10] have been synthesized previously.Recently we investigated [11] the chemical properties of N-2-H-tetrafluoroethyl derivatives of pyrrole and imidazole, and found conditions for nitrating, halogenating, and acylating such compounds. As a continuation of investigations in this area we have studied the chemical properties of N-difluoromethyl and N-2H-tetrafluoroethylpyrazoles 1a-d. N N R R (CF 2 ) n H 1a-d a R = H, b R = Me, с R = H, d R = Me; a, b n = 1, c, d n = 2Difluoromethylation of pyrazole, and of 3,5-dimethylpyrazole was carried out in aqueous dioxane medium by the action of chlorodifluoromethane and alkali. N-Difluoromethylpyrazole 1a proved to be an extremely volatile compound. It forms an azeotropically boiling mixture with water and diethyl ether. It is __________________________________________________________________________________________

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Cited by 31 publications

References 7 publications

Chemical approach for the syntheses of GM4 isomers with sialic acid to non-natural linkage positions on galactose

Chemical approach for the syntheses of GM4 isomers with sialic acid to non-natural linkage positions on galactose

Stereochemistry of conjugate halogenation of 1-phenyltricyclo[4.1.0.02,7]heptane

Chemical properties of derivatives of N-difluoromethyl-and N-2-H-tetrafluoroethylpyrazoles

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