Disparate behavior of ketones and thioketones on reaction with organolithiums

The reactions of alkyllithiums with ketones and thioketones proceed in fundamentally different ways. Whereas alkyllithiums add to the carbonyl carbon of ketones to give tertiary alcohols, the reaction with thioketones proceeds to give secondary thiols by reduction of the CS group. Transition states for the addition and reduction reactions of acetone and thioacetone in ethereal solution have been located and the computed activation free energies are in agreement with the observed behavior of ketones and thioketones in reactions with alkyllithiums.     

Ferrocenyl hetaryl thioketones: A computational study of their conformational stability

In this work, the conformational behavior of ferrocenyl- and hetaryl-functionalized thioketones was studied by means of computational quantum chemical methods. Four hetaryl substituents (furan-2-yl, thiophen-2-yl, selenophen-2-yl, and N-methylpyrrol-2-yl) were taken into account. The conformational space of the four ferrocenyl hetaryl thioketones was explored, and all found conformers were characterized using density functional (B3LYP) and wave function (SCS-MP2) theories. Their stability was explained in terms of intramolecular interactions. Such interactions were described using the methods of natural bond orbitals, “atoms in molecules,” noncovalent interaction index, and localized molecular orbital energy decomposition analysis. The identified conformations essentially differ in the arrangement of hetaryl heteroatom relative to the thiocarbonyl sulfur atom. The furan-2-yl substituent favors an s-trans-like arrangement of its heteroatom, while the remaining hetaryl substituents tend to adopt an s-cis-like arrangement. Such a conformational preference mainly results from the π → π* stabilization between the CS group and the hetaryl ring. Weak intramolecular hydrogen bonding of C H⋯O type was detected in the preferred conformer of ferrocenyl furan-2-yl thioketone. Low-polarity solvents, such as toluene, chloroform, and tetrahydrofuran, have a small effect on the preferred conformers of the four thioketones.     

Contrasting reactions of ketones and thioketones with alkyllithiums: a coordinated experimental and computational investigation

The reaction of ketones with organolithium reagents generally proceeds by addition of the organometallic to the electrophilic carbon of the C═O group to give the lithium salt of a tertiary alcohol. The seemingly analogous reaction of thioketones with organolithiums is a fundamentally different process: such reactions typically afford a variety of products, and addition of the organolithium to carbon of the C═S group to give a thiol is a relatively unimportant component. Reactions of the stable thioketone, adamantantanethione (1), with several alkyllithiums (MeLi, n-BuLi and t-BuLi) in a variety of solvents have been studied in the first comprehensive investigation of the reactions of organolithiums with a representative alkyl-substituted thione. Reactions of 1 with n-BuLi or t-BuLi afforded 2-adamantanethiol (2) as the major product. In an effort to explain the marked difference in behavior of ketones and thioketones in reactions with organolithiums, transition states for both the addition and reduction reactions have been located at the B3LYP/6-311+G* level using acetone and thioacetone as model substrates. The transition states for the addition of dimeric MeLi to the C═O and C═S carbons of acetone and thioacetone were significantly different as a result of the small bond angles preferred by divalent sulfur, and this accounts for the much slower addition to a C═S carbon vis-à-vis a C═O group. Transition states for reduction of acetone and thioacetone by EtLi were similar, but the greater exothermicity of the reduction of the thioketone results in an earlier transition state and lower activation energy for this process than that for the reduction of a ketone. The possible role of radical-mediated processes in this chemistry is also discussed.     

二氯亚甲基环已烷的卤化反应和2-取代二氯亚甲基环已烷的构象

多卤代烃在有机反应机理和结构研究中有着重要意意, 作为一个有用的合成中间体,其制备地受到人们重视,本文在此报导二氯亚甲基环已烷与氯及溴的反应和其它有关反应的实验结果。     

Structure and basicity of ω-substituted ethynyl 2-thienyl ketones

By a comparison of the calculated and experimental dipole moments of ethynyl 2-thienyl ketones, it was shown that the S,O-cis conformation is the most probable one. The basicities of these compounds were estimated by means of IR spectroscopy from the shift of the band of the phenolic OH stretching vibration. The correlation relationships between the dipole moments of the ketones, their basicities, and the association constants of propiolic acids that have identical substituents attached to the triple bond were established. It is noted that the experimental characteristics found do not correlate with the different sorts ofσ substituent constants; this provides evidence for a difference in the mechanism of the interaction of the atomic groups in a number of acetylenic and aromatic molecules.     

Three-component reaction for the C2-functionalization of 1-substituted imidazoles with acetylenic ketones and isocyanates

An efficient method for the direct C2-amidation of 1-substituted imidazoles with acetylenic ketones and isocyanates is reported. This three-component procedure has the advantages of catalyst-free, operational simplicity, mild reaction conditions, and good to excellent yields.     

Facile synthesis of 2-substituted 1,2-dihydro-1-naphthols and 2-substituted 1-naphthols

[reaction: see text] The palladium-catalyzed ring opening of dimethoxy oxabenzonorbornadiene with aryl or vinyl halides occurred under very mild conditions to give substituted 1,2-dihydronaphthols that were oxidized with IBX to furnish substituted naphthols in excellent overall yields.     

Conformers of diheteroaryl ketones and thioketones: a quantum chemical study of their properties and fundamental intramolecular energetic effects

The conformational behavior of ten diheteroaryl ketones and thioketones is investigated using various quantum chemical methods. These ketones and thioketones are formed by the disubstitution of formaldehyde and thioformaldehyde with such a heteroaryl group as 2-furanyl, 2-thiophenyl, 2-selenophenyl, 2-pyrrolyl or 1-methyl-2-pyrrolyl. For these compounds, their conformational preference and the energetic ordering of their conformers are determined at the MP2 and B3LYP levels of theory. Energetic barriers resulting from the interconversion between conformations are also estimated. The natural bond orbital (NBO) and interacting quantum atoms (IQA) methods are used to study fundamental intramolecular energetic effects influencing the stability of individual conformers. The results of the two methods indicate the great significance of the effect associated with electron delocalization (in the form of either NBO donor–acceptor interactions or the IQA interatomic exchange–correlation interaction energy) in governing the conformational behavior of the investigated diheteroaryl ketones and thioketones.     

Photoacoustic spectra of naphthalenes: 2-fluoro, 2-chloro, 2-bromo and 2-hydroxynaphthalenes

The photoacoustic spectra of 2-fluoro, 2-chloro, 2-bromo and 2-hydroxynaphthalenes have been recorded in the powder form. A method of analysing these spectra is suggested in the light of solution phase and vapour phase data on these molecules. It is observed that the non-radiative transitions in the region of 200 nm decrease in these molecules as the substituent in the 2-position is changed from F to Cl to Br to OH.     

Pyridazines,LVIII: 1-Phenyl-1-pyridazinyl-2-substituted ethenes,synthesis and configuration

Summary Starting from phenyl pyridazinyl ketones1 and3 various 1-phenyl-1-pyridazinyl-2-substituted ethenes (2 a–c, 4, 5 a, b, 6 a, b, 7–9) were prepared by Wittig-Horner- oder Wittig-type reactions. Configurational assignments of these novel compounds were achieved by NOE difference spectroscopy.Dedicated with best wishes to Prof. Dr. M. Pailer on the occasion of his 80th anniversary     

Synthesis of 1-substituted 2, 5-bischloromethylpyrrolidines

A number of 1-substituted 2, 5-bischloromethylpyrrolidines, cyclic analogs of bis-Β-chloroethylamine, have been synthesized. The previously unreported 1-phenyl- and 1-benzyl-2, 5-bis(N-cycloalkylaminomethyl)pyridines and their methiodides have been obtained.     

Spatial structure of β-substituted alkoxyvinyl trifluoromethyl ketones

Spatial structure of six β-substituted enones, with common structure R₁O–CR₂CH–COCF₃, were R₁ = C₂H₅, R₂ = H (ETBO); R₁ = R₂ = CH₃ (TMPO); R₁ = C₂H₅, R₂ = C₆H₅ (ETPO); R₁ = C₂H₅, R₂ = 4- O₂NC₆H₄ (ETNO); R₁ = C₂H₅, R₂ = C(CH₃)₃ (ETDO) were investigated by ¹H and ¹⁹F NMR, infrared spectroscopy and AM1 calculations. NMR spectra revealed that enones (MBO), (ETBO) and (TMPO) are exclusively (3E) isomers, whereas in (ETPO), (ETNO) and especially in (ETDO) the percentage of (3Z) isomers is significant and depends on the nature of solvents. Conformational behaviour of studied enones are determined by the rotation around of CC double bond, C–C and C–O single bonds (correspondingly trifluoroacetyl and alkoxy groups), and (EZZ) conformer being the most stable in all cases. IR spectra revealed that with the exception of (ETDO) (EZZ) conformer is most populated in all cases. Bulky substituents like phenyl or tert-butyl group at β-position of enone result in the equilibrium mainly between (EZZ) and (ZZZ) forms, whereas β-hydrogen and β-methyl substituents determine the equilibrium between (EZZ) and (EEZ) or (EZE) conformers.     

Synthesis of 1-substituted 2, 5-bischloromethylpyrrolidines

A number of 1-substituted 2, 5-bischloromethylpyrrolidines, cyclic analogs of bis--chloroethylamine, have been synthesized. The previously unreported 1-phenyl- and 1-benzyl-2, 5-bis(N-cycloalkylaminomethyl)pyridines and their methiodides have been obtained.     

Synthesis of 1-substituted trans-2-thiahydrindanes and 3-substituted trans-2-thiadecalins

Methods of synthesis of 1-R-trans-2-thiahydrindanes and 3-R-trans-2-thiadecalins from trans-1-methoxymethyl-2-chlorocyclohexane have been developed. The order of the chromatographic elution of the isomeric sulfides formed has been found. The configurations of the compounds have been established by¹H and¹³C NMR spectroscopy. The characteristics of the intermediate and final compounds are given. The splitting of 1-R-trans-2-oxahydrindanes and 3-R-trans-2-oxadecalins by the PBr₃/conc. HBr system has been effected.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1877–1884, August, 1991.     

Synthesis of 3-substituted trans-2-oxadecalins and 1-substituted trans-2-oxahydrindanes

A study was carried out of the intramolecular cyclization of trans-1-methoxymethyl-2-(1-hydroxyalkyl)cyclohexanes and trans-1-methoxymethyl-2-(2-hydroxyalkyl)cyclohexanes by the action of acid chlorides of phosphorous, sulfurous and p-toluenesulfonic acids with the formation of 1-substituted trans-2-oxahydrindanes in low yields and 3-substituted trans-2-oxadecalins in high yields. A relationship has been established between the yields of the cyclization products and the nature of the halogenating agent. The cyclization does not proceed via an intermediate oxonium ion, but by means of an intermolecular electronic transition.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1865–1877, August, 1991.     

Synthesis and intramolecular pericyclization of 1-azulenyl thioketones

Several azulene-substituted thioketones, 1-thiobenzoylazulene (1a) and di(1-azulenyl) thioketone (2a) and their derivatives (1b and 2b-d) with alkyl substituents on each azulene ring, were prepared and their intramolecular pericyclization reaction was examined. The thioketones with a 3-alkyl substituent on each azulene ring exhibited the presumed pericyclization reaction under thermal and acid-catalyzed conditions, although the cases of the 1-azulenyl thioketones without the 3-alkyl substituents afforded a complex mixture under similar conditions. The intramolecular reaction following the intramolecular hydrogen transfer afforded the products 13b, 14b, and 14c. The products 13b and 14b were converted into the corresponding cations 18(+) and 19(+), which have structural similarity with that of the phenalenyl cation. These cations exhibited the expected two-step reduction waves upon CV, although the ESR analysis revealed that the neutral radical state did not have the presumed high stability.     

Influence of the solvent on the activation parameters of the conformational conversions of 2-substituted 1, 3-dithia-5,6-benzocycloheptenes

Conclusions The enthalpy and entropy of activation of the chair(e)-boat(e) interconversion for 2-substituted 1,3-dithia-5,6-benzocycloheptenes depend significantly on the type of the solvent, whereby the changes in the enthalpy of equilibrium and of activation are not determined by the same factors when the solvent is changed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1253–1256, June, 1989.     

Synthesis of 4-substituted chlorophthalazines, dihydrobenzoazepinediones, 2-pyrazolylbenzoic acid, and 2-pyrazolylbenzohydrazide via 3-substituted 3-hydroxyisoindolin-1-ones

Herein we describe a general three-step synthesis of 4-substituted chlorophthalazines in good overall yields. In the key step, N,N-dimethylaminophthalimide (8a) directs the selective monoaddition of alkyl, aryl, and heteroaryl organometallic reagents to afford 3-substituted 3-hydroxyisoindolinones 9b, 9i-9am. Many of these hydroxyisoindolinones are converted to chlorophthalazines 1b-1v via reaction with hydrazine, followed by chlorination with POCl(3). We have also discovered two novel transformations of 3-vinyl- and 3-alkynyl-3-hydroxyisoindolinones. Addition of vinyl organometallic reagents to N,N-dimethylaminophthalimide (8a) provided dihydrobenzoazepinediones 15a-15c via the proposed ring expansion of 3-vinyl-3-hydroxyisoindolinone intermediates. 3-Alkynyl-3-hydroxyisoindolinones react with hydrazine and substituted hydrazines to afford 2-pyrazolyl benzoic acids 16a-16d and 2-pyrazolyl benzohydrazides 17a-17g rather than the expected alkynyl phthalazinones.     

Asymmetric transfer hydrogenation of α,β-unsaturated, α-tosyloxy and α-substituted ketones

Asymmetric transfer hydrogenation of cyclic and acyclic α,β-unsaturated ketones catalysed by η⁶-p-cymene/ruthenium(II) and η⁵-pentamethylcyclopentadienyl/rhodium(III) complexes have been investigated. Cyclic α,β-unsaturated ketones appeared to be more suitable substrates for the synthesis of enantiomerically pure allylic alcohols than do acyclic α,β-unsaturated ketones. A proposed mechanism for the formation of 4-phenyl-[1,3]-dioxolan-2-one from α-tosyloxy- and halo-substituted acetophenones is discussed. The results of further investigations into the reduction of a range of α-tosyloxyacetophenones and the dynamic kinetic resolution of α-substituted ketones is presented.