Nucleophilic reactions of fluoroolefins.IV. Regioselectivity in the reactions of 1-phenylpentafluoropropenes with alkyllithium reagents

Reactions of 1-phenylpentafluoropropenes $\text{1a}$–$\text{c}$ with a number of alkyllithium reagents were investigated in detail. In all cases mixtures of 1-alkly-1-phenyltetrafluoropropenes $\text{2}$ and 2-alkyl-1-phenyltetrafluoropropenes $\text{3}$ were obtained. The ratio of products $\text{2}$ and $\text{3}$ is strongly influenced by both the electronegativity of the benzene ring substituents and the bulk of the alkyl group of the alkyllithium reagents. The increase of both of these factors favours formation of 2-alkyl-substituted alkenes $\text{3}$ with a reduced yield of 1-alkyl-substituted alkenes $\text{2}$. The influence of the benzene ring substituents in alkenes $\text{1}$ obeys the Hammett type correlation, while the influence of the bulk of the alkyllithium reagents exhibits good relationships with the Fellous and Luft scale of steric substituent constants E^x_s ; no linear correlation with other scales of steric constants was found. Overall regioselectivity, in the reaction of 1-phenylpentafluoropropenes $\text{1}$ with alkyllithium reagents, considering both the influence of the benzene ring substituents and steric factors, is expressed by the Pavelich-Taft type equation. Observed direction of the influence of the bulk of the alkyllithium reagents on the ratio of products $\text{2}$ and $\text{3}$ is interpreted in terms of steric strains influencing the geometry and free energy of the supposed intermediates involved in these reactions.     

Nucleophilic reaction of fluoroolefins. V. Regioselectivity and stereochemistry in the reactios of 1-phenylpentafluoropropenes with lithium dialkylamides

1-Phenylpentafluoropropenes $\text{1}$ readily react with lithium dialkylamides to give, in most cases, mixtures of 1-aminosubstituted alkenes $\text{2}$ and 2-amino-substituted alkenes $\text{3}$, with the latter being the favoured products. The reactions with bulky lithium diethylamide and lithium 2-methylpiperidinoamide gave exclusively 1-amino-substituted products $\text{2}$. The effect of the increased bulk of N-nucleophiles is opposite to that observed for the reactions of alkenes $\text{1}$ with C-nucleophiles Increasing electronegativity of the phenyl ring substituents in alkenes $\text{1}$ shifts the regioselectivity of the attack of lithium amides towards the C2 carbon atom. The E to Z isomer ratios of enamines $\text{2}$ were found to be time dependent and the slow isomerisation of the kinetic isomers E to the thermodynamic isomers Z was observed, while the ratio of isomers of enamines $\text{3}$ did not change with time.A concerted, single-step process is suggested for the reactions of alkenes $\text{1}$ with lithium dialkylamides, and a tentative explanation of the different stereochemistry of enamines $\text{2}$ and $\text{3}$ is given.     

Nucleophilic reactions of fluoroolefins. I. Reactions of 1-(2-tetrahydrofuryl)-pentafluoropropene with alkoxide ions

Unlike unsubstituted perfluoropropene [1,2] 1-(2-tetrahydrofuryl)-pentafluoropropene $\text{1}$ reacts with sodium alkoxides in parent alcohol solutions to give 1-alkoxy-1-(2-tetrahydrofuryl)-tetrafluoropropenes $\text{2}$ as major products and 1-alkoxy-2H-1-(2-tetrahydrofuryl)-pentafluoropropanes $\text{3}$ as very minor products. The yield of adducts $\text{3}$ is, to some extent, increased by the reduced basicity of the alkoxide ion. Results are discussed in terms of the supposed properties of the carbanionic intermediates involved.N.m.r., m.s., and i.r. data for, and some chemical properties of compounds $\text{2}$, viz., further reactions with sodium alkoxides and hydrolysis are described.     

Mechanisms of elimination reactions—XXVII: The reactions of 1-arylethyldimethylsulfonium bromides with sodium ethoxide in ethanol

Treatment of 1-phenylethyldimethylsulfonium bromide 1 with sodium ethoxide in ethanol at 35° affords four products by five reaction paths: styrene 2 by E2 and α'-β mechanisms, ethyl 1-phenylethyl ether 3 and methyl 1-phenylethyl sulfide 4 by the S_N2 mechanism, and methyl o-ethylbenzyl sulfide 5 by a Sommelet-Hauser rearrangement. Isotope effects of 5.9 and 3.5 for E2 and α'-β reactions were estimated by comparing the deuterium content of methyl sulfide from β-d₃, and α-d₇ (all α-positions exchanged) sulfonium salt. Product analyses on products from the unsubstituted, p-methyl, p-fluoro, p-bromo and m-chloro sulfonium salts were combined with overall rates to calculate partial rates for the formation of each product. These partial rates were fitted to the Hammett equation to give values for each product as follows: 2, 0.95±0.19; 3, ?0.63±0.41; 4, 0.95±0.11; 5, 4.84±0.38. The mechanistic implications of the results are discussed.     

Synthesis of ethylaminopyridines by the reaction of isomeric benzaldehyde pyridylhydrazones with sodium ethoxide

The reaction of isomeric benzaldehyde pyridylhydrazones with alkali metal alkoxides gave 2-, 3-, and 4-ethylaminopyridines. The effect of temperature and reaction time on the yields of products was investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 351–353, March, 1972.     

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。     

Regioselectivity in the Addition of Nucleophilic Reagents to 1-Alkylthio-2-polyfluoroalkylacetylenes

Calculations for HCCH, HCCCF₃, and H₃CSCCCF₃ were carried out using the MP2(f)/6-31G(d) nonempiric quantum-chemical method. The electronic structure and charge density distribution were examined using natural bond orbitals and the results account for the differences in the direction of nucleophilic attack of the triple bond in HCCCF₃ and H₃CSCCCF₃.     

Nucleophilic substitution reactions of 1-methyl-4,5-dinitroimidazole with aqueous ammonia or sodium azide

Chemistry of Heterocyclic Compounds - In this work, 5-amino-1-methyl-4-nitroimidazole was synthesized by amination reaction of 1-methyl-4,5-dinitroimidazole with aqueous ammonia in 95% yield....     

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.     

Photoaddition reactions of fluoroolefins with diols and cyclic ethers

Fluoroalkylation of aliphatic diols, tetrahydrofuran and 1,3-dioxolanes with perfluoroolefins under photochemical initiation was studied. The aim of the study was the preparation of fluoroalkylated diols as intermediates for special fluorinated monomers. Fluoroalkylation was only partly successful in the case of 1,4-butanediol and quite successful with tetrahydrofuran and 2,2-dimethyl-1,3-dioxolane. The fluoroalkyl diols obtained were converted to monomethacrylates that are amphiphilic monomers.     

Regioselectivity in the reactions of diphenylnitrilimine with coumarin and chromone

The cycloaddition of diphenylnitrilimine with coumarin and chromone gave the cycloadducts 4 and 5 respectively. The structures of these products were based on elemental and spectral analyses and alternate synthesis. The orientations of the cycloaddition are interpreted in terms of FMO theory.     

Regioselectivity in the reactions of polyfunctionalised pyrroles with nucleophiles

The polyfunctionalised pyrrole, 3,5-dichloro-1H-pyrrole-2,4-dicarbaldehyde reacts with secondary amines by condensation with the 2-carbaldehyde to give methylene-substituted pyrroles, while its N-alkyl derivatives undergo substitution of the 5-chloro group to give 5-substituted pyrroles.     

Regioselectivity in reactions of alkynylmetal complexes with pyrimidinones

Regioselectivity is observed in $\text{1}\text{1}$-adduct formation between phenylethynyltriisopropoxytitanium and 2(1/H)-pyrimidinones; the new carbon-carbon bond is formed at C(4). In contrast the 3,4- and 3,6-dihydro products are formed together from the corresponding magnesium and lithium reagents, but from the magnesium compound the major product is the 3,6-dihydro isomer. Ethynylmagnesium bromide gives equimolar amounts of the 3,4- and 3,6-dihydro isomers. Dehydrogenation of the products gives the alkynylated aromatic heterocycles.     

Study of the cleavage of the N-N bond in the reaction of benzaldehyde pyrazinyl-, pyridazinyl-, and pyrimidinylhydrazones with sodium ethoxide

The reaction of benzaldehyde pyrazinyl-, pyridazinyl-, and pyrimidinylhydrazones with sodium ethoxide was investigated by means of gas—liquid chromatography (GLC) and mass chromatometry. It was established that the previously discovered new type of cleavage of the N-N bond in pyridylhydrazones under the influence of alkali-metal alkoxides also takes place in a number of azine systems, but the yields of the corresponding N-monoalkylamino derivatives of pyrazine, pyrimidine, and pyridazine differ.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1120–1124, August, 1978.