- Colloid and nanosized catalysts in organic synthesis: XII. Hydrogenation of carbonitriles catalyzed by nickel nanoparticles
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Hydrogenation of carbonitriles catalyzed by nickel nanoparticles in isopropanol proceeds under atmospheric pressure of hydrogen within 6-15 h to yield mainly secondary amines. Hydrogenation of α-aminonitriles results in reductive decyanation. β-Aminonitriles undergo hydrogenolysis at the nitrogen-carbon bond.
- Mokhov,Popov,Shcherbakova
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p. 273 - 280
(2016/04/20)
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- Application of alkoxy-λ6-sulfanenitriles as strong alkylating reagents
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Alkoxy-λ6-sulfanenitriles were found to be versatile alkylating reagents toward various nucleophiles bearing at least one proton such as methanol, phenol, thiophenols, carboxylic acids, ptoluenesulfonic acid, hydrochloric acid, and primary and secondary amines. Reactivity of the alkoxy group of the λ6-sulfanenitriles showed an opposite trend to the usual SN2 character, i.e. Me (la), Pr (1b), and Bu (1d) ? i-Pr (1c). In the presence of p-TsOH, alkyl tosylates were predominantly formed instead of the alkylation products of nucleophiles. In addition, even a sterically hindered substrate, neopentyloxy-λ6-sulfanenitrile, was found to undergo an SN2 reaction toward thiophenol without any rearrangement product to give neopentyl phenyl sulfide in good yield.
- Hao, Wei,Fujii, Takayoshi,Dong, Tiaoling,Wakai, Youko,Yoshimura, Toshiaki
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p. 193 - 198
(2007/10/03)
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- Kinetics and Mechanisms of Nucleophilic Displacements with Heterocycles as Leaving Groups. Part 22. Reactions with Various Nucleophiles and a Study of the Effects of Substrate Concentrations, Traces of Water, ands Nature of the Gegenion on the Rates
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First- and second-order rate components for the nucleophilic displacements of a variety of N-(primary alkyl), N-(secondary alkyl), and N-benzyl substituents from mono-, bi-, and tri-cyclic pyridine leaving groups by various nucleophiles are independent of substrate concentration, of the nature of the gegenion, and of traces of water in the solvent.Thus assumptions implicit in the reasoning of earlier papers of this series are confirmed, and the conclusion that these nucleophilic displacements can proceed by five independent mechanistic pathways is strengthened.First-order rate components are invariant with the nature of the nuclephile.Second-order rate components vary with nucleophile nucleophilicity in a way that parallels Menschutkin reactions.Activation enthalpies for first-order components are less negative than those for second-order components, in agreement with previous data.
- Katritzky, Alan R.,Schultz, Hanna,Lopez-Rodriguez, Maria L.,Musumarra, Giuseppe,Cirma, Giuseppe
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- Conveniant Method for Replacement of Tertiary N-Methyl by Other Alkyl Groups: Application to Morphine Alkaloids
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The replacement of N-methyl of N-methylpiperidine (1), 4-methylmorpholine (4), 2-methyl-1,2,3,4-tetrahydroisoquinoline (7) and tropine (10) by n-propyl, n-butyl and isopropyl groups (3a-3c, 6c, 9a-9c and 12a-12c) has been achieved in high yields by quaternization of the respective tertiary amine with appropriate alkyl halide and demethylation of the resulting quaternary salt with thiophenoxide.It has been established that demethylation is strongly favoured over the removal of n-propyl and n-butyl groups, whereas deisopropylation occurs to some extent.Surprisingly, in the case of 11c, deisopropylation predominates.This method has been applied to morphine (13b), codeine (13d) and thebaine (14b) for similar replacements.The rapid quaternization of thebaine (14b) has been assigned to the absence of H-14 in this alkaloid.The fact that quaternary salts of thebaine, which are susceptible to aromatization of the nucleus by extrusion of the ethanamine chain, are smoothly demethylated to N-alkylnorthebaines (18a-18c) in good yields indicates that demethylation, a bimolecular nucleophilic displacement, competes very successfully with elimination reaction.
- Manoharan, T. Samuel,Madyastha, K. Madhava,Singh, B. B.,Bhatnagar, S. P.,Weiss, Ulrich
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- 2- and 4-(α-Substituted Aryl)pyridines as Leaving Groups in SN2 Reactions and Radicaloid Nucleophilic Displacements.
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Compared with 2,4,6-triphenylpyridine, 2,6-diphenyl-4-(o-substituted phenyl)pyridines as leaving groups in the radicaloid nucleophilic displacement reaction with 2-nitropropanide anion slow down C.T.C. formation. o-Substitution of the 2-phenyl group has little effect on this reaction.The latter modification however decreases SN2 rates of the corresponding pyridiniums with piperidine.
- Katritzky, Alan R.,Elisseou, E. Michael,Bashiardes, George,Patel, Ranjan C.
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p. 301 - 320
(2007/10/02)
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- Kinetics and Mechanisms of Nucleophilic Displacements with Heterocycles as Leaving Groups. Part 5. Solvent Effects
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First- and second-order rates for the reactions of 1-methyl-, 1-isopropyl-, 1-s-butyl-, 1-benzyl-, and 1-p-methoxybenzyl-2,4,6-triphenylpyridiniums with piperidine in chlorobenzene in protic and dipolar aprotic solvents are reported.For the 1-isopropyl, 1-s-butyl and 1-p-methoxybenzyl derivatives the bimolecular reaction is accompanied by a unimolecular process in all solvents.Second-order rate constants for the 1-methyl and for the 1-benzyl compounds are correlated with the ET solvent parameter.Principal component analysis of second-order rates provided a three-component model.The first component differentiates aprotic solvents from protic ones, while the second component is linearly related to the basicity parameter B for aprotic solvents.
- Musumarra, Giuseppe,Ballistreri, Francesco P.,Muratore, Salvatore,Katritzky, Alan R.,Wold, Svante
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p. 1049 - 1054
(2007/10/02)
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- UNIMOLECULAR AND BIMOLECULAR TRANSFER OF N-SUBSTITUENTS FROM PYRIDINIUM CATIONS: EVIDENCE FOR A CLEAR MECHANISTIC CHANGEOVER
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N-Substituents in 2,4,6-triphenylpyridiniums are transferred to piperidine, morpholine and pyridine by unimolecular and/or bimolecular processes in chlorobenzene solution.These processes are quite distinct and afford no evidence for a mechanism intermediate between SN1 and SN2.
- Katritzky, Alan R.,Musumarra, Giuseppe,Sakizadeh, Kumars,El-Shafie, Sayed M. M.,Jovanovic, Bratislav
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p. 2697 - 2699
(2007/10/02)
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