Nucleophilic identity substitution reactions. The reaction between ammonia and protonated amines

The gas phase reactions between NH3 and the protonated amines MeNH3+, EtNH3+, PriNH3+, and Bu(t)nH3+ have been studied by high level ab initio methods. Mass spectrometric experiments yielded no significant reaction products; this result being consistent with the calculated reaction barriers. The potential energy profiles for both nucleophilic substitution (SN2) and elimination (E2) pathways have been investigated. Both back side Walden inversion (SNB) and front side (SNF) nucleophilic reaction profiles have been generated. The SNB reaction barriers are found to be higher for the more alkyl substituted reaction centres. Reaction barrier trends have been analysed and compared with the results of a similar study of the H2O-ROH2+ system (R = Me, Et, Pri, and Bu(t)).     

Nucleophilic identity substitution reactions. The reaction between water and protonated alcohols

The potential energy surfaces for the reaction between H2O and the protonated alcohols MeOH2+, EtOH2+, PriOH2+, and Bu(t)OH2+ have been explored by means of high level ab initio theoretical methods. Both nucleophilic substitution (SN2) and elimination (E2) pathways have been investigated. Front side (SNF) and the familiar back side (SNB) Walden inversion attack of the nucleophile have been found to be competing for the H2O Bu(t)OH2+ system. In contradiction with the customary relationship between so-called "steric effects" and barrier heights--more alkyl-substituted SN2 reaction centres have higher SN2 reaction barriers--the SN2 reaction barriers are found to be Et > Me > Pri > Bui. This result is in excellent agreement with available experimental data.     

Base-promoted elimination of hydrogen fluoride from alkyl fluorides : Reactivity and stereochemistry

The alcoholate promoted dehydrohalogenation of S-nonyl fluoride and cyclododecyl fluoride, typical straight-chain and, respectively, medium-size cyclic substrates, leads to cis- and trans-alkenes in an approximate ratio of 1 : 3. With bulky bases such as lithium diisopropylamide the trans isomer may be obtained almost exclusively. In general, the elimination of hydrogen fluoride proceeds very slowly. Increase of the base strength has only a moderate effect on the rates. Electrophilic assistance as provided by lithium cations in media of low polarity can, however, considerably accelerate the reaction. - Cyclododecyl fluoride cannot be prepared from cyclododecanol. It is, however, readily accessible by bromofluorination of cyclodecene and subsequent reduction of the adduct with stannane.     

Nucleophilic substitution reactions of 1-sulfonyl substituted cyclopropenes with alkyl lithium reagents

Sulfonyl substituted cyclopropenes react with a variety of alkyl lithium reagents to give disubstituted cyclopropenes in good yield.     

多氟芳烃的亲核反应I.仲胺作为亲核试剂

本文报道全氟苯、一氯五氟苯和二氯四氟苯与仲胺在DMF或HMPA中的亲核反应结果,C6F5Cl与仲胺反应生成对位产物,C6F4Cl2(m:o:p)=73:18:9)与仲胺的反应,只有m-和o-异构体能生成预期产物,而p-C6F4Cl2只与活性高的四氢吡咯反应,延长反应时间和提高反应温度,C6F6可给出对双取代产物,六个仲胺的反应活性顺序是:四氢吡咯>哌啶>吗啡啉>二乙胺>二正丙胺>二异丙胺。     

Reactions involving fluoride ion. Part 21 [1]. Nucleophilic substitution reactions of perfluorocyclobutene oligomers

Reaction of perfluorocyclobutene oligomers, (1) - (4), with some simple nucleophiles gives products arising from S_N2′ displacement [N.B. this term is used here to describe the overall process of addition of a nucleophile to an alkene and elimination of an allylic fluorine and is not meant to imply that the reaction is concerted] or vinylic substitution of fluorine, or a mixture of both processes. The reactivity of the dimers, (1) and (2), is much greater than that of acyclic analogues and this can be attributed to the ring strain present in these compounds.     

Benzothiazolium derivatives. III. Nucleophilic substitution reactions of benzothiazolium salts

The reactions of 2,3-dihydrothiazolo[2,3-b]benzothiazolium bromide 1 (A^? ?Br^?) with certain nucleophilic reagents have been performed for the purpose of ascertaining the reaction pathways and identifying the group that is displaced from the central carbon atom of the dithiocarbamate system. The nature of complex salt-like intermediates formed initially from 1 (A^? ?Br^?) has been studied and confirmed. For comparison, a number of nucleophilic substitution reactions of 2-methylthio-3-methylbenzothiazolium iodide 17 and 2-dimethylamino-3-methylbenzothiazolium perchlorate 18 have been examined.     

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.     

Nucleophilic character of alkyl radicals. XIV. Homolytic δ-aminoalkylation of protonated quinoxaline

A new general reaction of wide synthetic interest, involving homolytic δ-aminoalkylation of quinoxaline in acidic medium, is described. Primary and secondary alkylamines, through the corresponding N-chloroamines, and tertiary alkylamines, through the corresponding N-oxides, are used. The mechanism of the reaction, involving intramolecular hydrogen abstraction by amino radical cations, and the unusual selectivity are discussed in terms of nucleophilic character of the alkyl radicals and of polar effects in the aromatic substitution.     

Azaindole derivatives. 60. Nucleophilic substitution reactions in 6-chloro-5-azaindolines

Reactions involving nucleophilic substitution of the halogen atoms in 1-benzyl-6-chloro-7-cyano-5-azaindoline by alkoxy groups and residues of various amines were investigated. The effect of electron-acceptor substituents on the saponification of the alkoxy groups to give hydroxy groups is demonstrated. The effect of the character of the fusion of the pyridine and pyrrole rings on the ease of nucleophilic substitution is examined.See [1] for Communication 59.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1648–1653, December, 1981.     

Hydrolysis reactions of transition metal fluorides in liquid hydrogen fluoride: Oxonium salts with Nb,Ta and W

The hydrolysis reactions of the hexafluorides of molybdenum and tungsten, the pentafluorides of niobium and tantalum and the tetrafluorides of zirconium and hafnium have been studied in liquid hydrogen fluoride. The following new compounds have been isolated and characterized: H₃O⁺WOF^-₅, H₃O⁺NbF^-₆ and H₃O⁺TaF^-₆. Hydrolysis of MoF₆ leads to MoOF₄, but in HF solution there is evidence for the existence of MoOF^-₅ ion.     

Addition reactions of alkyl and carboxyl radicals to vinylidene fluoride

The addition reactions of alkyl radicals CF3* and CH3* and carboxyl radicals C2H5O*, C2H5OCOO*, CF3COO*, and CH3COO* to a vinylidene fluoride (VDF) molecule are studied using ab initio calculations. These radicals were selected because they are intermediate or final products of diacyl peroxides decomposition in the initiation reactions of VDF polymerization. Two combinations of methods for energetics and structure optimization are applied: QCISD/6-311G(d,p)//HF/6-31G(d) and B3LYP/6-311G+(3df, 2p)//B3LYP/6-31G(d). It is found that the formed bond length of the product, the forming bond length of the transition state, and the attack angle of the product structures are not sensitive to the level of theory even though the attack angle of the transition state structures is. Early transition states are obtained upon attack at both high-substituted and nonsubstituted carbon atom VDF ends. Kinetic and thermodynamic control rules play different roles on governing the reactivity of the addition with the studied radicals. Both theoretical methods yield the same trends for the preferential attack site in terms of regioselectivity, barrier energies, and reaction enthalpies. It is shown that the addition reactions of the intermediate radicals C2H5OCOO*, CF3COO*, and CH3COO* of the decomposition of diethyl peroxydicarbonate, trifluoroacetyl peroxide, and diacetyl peroxide initiators yield smaller energy barriers than the additions of the corresponding final radicals, C2H5O*, CF3*, and CH3*; therefore, the reactions of the intermediate radicals should not be ignored when analyzing the initiation process of the VDF polymerization using those initiators.     

Nucleophilic substitution of alkyl halides by zinc salts-32 preparation of tertiary alkyl esters and ethers under non-solvolytic conditions

Zinc salts of carboxylic acids, phenols and alcohols are found to react with tertiary alkyl halides in nonpolar solvents and in presence of a base yielding the corresponding esters and ethers in moderate to good yields.     

Nucleophilic substitution reactions of 1,4-dichlorobenzene chromium tricarbonyl with mono- and diphenoxides

The nucleophilic substitution reactions of 1,4-dichlorobenzene chromium tricarbonyl ( 1 ) with the phenoxide anion were investigated. The substitution of the first chlorine was very fast and gave the mono-substituted product in high yield. The substitution of the second chlorine group was significantly retarded by the presence of the phenoxy group incorporated during the first reaction and also due to the competing decomplexation reaction. The application of 1,4-dichlorobenzene chromium tricarbonyl ( 1 ) to the synthesis of new monomers was demonstrated by the preparation of 2,2′-bis[4-(4-chlorophenoxy)phenyl]propane ( 9 ). 2,2′-Bis[4-(4-chlorophenoxyl)phenyl]propane ( 9 ) was synthesized by a nucleophilic substitution reaction of 4,4′-isopropylidenediphenolate with 1,4-dichlorobenzene chromium tricarbonyl ( 1 ) followed by decomplexation with I₂. 2,2′-Bis[4-(4-chlorophenoxy)-phenyl]propane ( 9 ) was also synthesized via a three-step reaction starting from the nucleophilic substitution reaction of 4,4′-isopropylidenediphenol ( 7a ) with 1-chloro-4-nitrobenzene ( 10 ). 2,2′-Bis[4-(4-chlorophenoxy)phenyl]propane ( 9 ) was polymerized by a Ni(0)-catalyzed reaction to yield amorphous aromatic polyethers with number-average molecular weights of up to 11,200 g/mol. © 1993 John Wiley & Sons, Inc.