99232-42-5Relevant academic research and scientific papers
Domino Friedel-crafts-type cyclizations of difluoroalkenes promoted by the α-cation-stabilizing effect of fluorine: An efficient method for synthesizing angular PAHs
Fuchibe, Kohei,Jyono, Hideharu,Fujiwara, Masaki,Kudo, Takao,Yokota, Misaki,Ichikawa, Junji
experimental part, p. 12175 - 12185 (2011/12/01)
In order to synthesize polycyclic aromatic hydrocarbons with nonlinear arrangements (angular PAHs), acid-promoted domino cyclizations of 1,1-difluoroalk-1-enes and 1,1-difluoroalka-1,3-dienes were studied. 1,1-Difluoroalkenes, each bearing two aryl substituents, were regioselectively protonated with FSO3H·SbF5 to generate fluorine-stabilized carbocations, which readily underwent domino Friedel-Crafts-type cyclizations to give carbocycles based on 6/n/m/6 ring systems (n,m=5-7) in good to high yields. Protonation of 1,1-difluoroalka-1,3- dienes took place at their electron-rich methylene (CH2) carbon atoms in the presence of milder acids such as camphorsulfonic acid and trifluoromethanesulfonic acid. Domino cyclizations of the resulting fluorine-stabilized allylic carbocations afford carbocycles based on 6/6/6/6 or 6/6/5/6 ring systems in high yields.
QUANTUM CHEMICAL CALCULATIONS AND NUCLEAR MAGNETIC RESONANCE MEASUREMENTS ON BENZYL-TYPE CARBANIONS. PART 2. INFLUENCE OF COUNTERCATIONS AND INTERACTING UNSATURATED SYSTEMS
Vanermen, Guido,Toppet, Suzanne,Van Beylen, Marcel,Geerlings, Paul
, p. 707 - 714 (2007/10/02)
Quantum chemical calculations, n.m.r. and spectrophotometric measurements are carried out to study the influence of countercations and interacting unsaturated systems on the structural and electronic properties of benzyl-type carbanions.The calculated geometry of benzyl-Li compares favourably with X-ray data on a related structure. (13)C, (1)H n.m.r. shifts and 1JCH coupling constants of benzyl, o- and p-CH3O-benzyl-Li, -Na, and -K compounds show a fair overall agreement with the ab initio-calculated charge distributions and structural parameters for the terminal members of the Li-, Na-, and K- series, the Li compound and the free carbanion, modelling the K salt.Both theory and experiment indicate that, when passing from the anion to the alkali-metal compound, an important destruction of the resonance saturation, present in the CH3O derivatives, occurs due to the presence of the countercation, the reduction being more important with decreasing cation radius.The n.m.r. data for α-alkyl-substituted compounds suggest that steric factors make the position of the cation in the Cα region less favourable, the effect being more pronounced for larger cation radius.The resonance saturation effect in the above mentioned systems may also be influenced by intermolecular effects, e.g. it may change during a chemical reaction.Ab initio calculations on the interaction energy between the benzyl-type carbanions and unsaturated systems showing increasing delocalization possibilities for incoming negative charge indicate that the larger this delocalization possibility (ethene butadiene styrene), the more important the destruction of resonance saturation.Along this series the parallel conformation of the CH3O group in the p-CH3O compounds gradually becomes less disfavoured.The calculated effect is however not strong enough yet in order to show full agreement with the observed increase in the k(-) value for the addition reaction to 1,1-diphenylethene when passing from polystyryl to poly-p-methoxystyryl carbanions.Larger basis sets and extensive geometry optimization should be carried out in order to settle this problem.
Dissociation Behavior of Benzylalkali Compounds in Tetrahydrofuran: Effect of Countercation, Aromatic Methoxy Substitution, and α-Alkyl Substitution
Vanermen, G.,Beylen, M. Van,Geerlings, P.
, p. 603 - 607 (2007/10/02)
Conductometric measurements are carried out on different benzylalkali compounds (benzylcesium, -potassium, -sodium, and -lithium, and their o-CH3O and p-CH3O derivatives) in tetrahydrofuran at various temperatures, in order to get information on their dissociative behavior and on the influence of the alkali cation, aromatic methoxy substitution, and α-alkyl substitution on the carbon-metal bond strength.The dissociation constants of the organometallic compounds are determined by using the Kraus and Bray equation, the Fuoss equation, the Wooster equation, or by curve fitting depending on which species are involved in the solution conductance.Temperature variation of Kd is used to determine the enthalpy and entropy of dissociation.The information previously acquired by quantum chemical calculations and NMR measurements on the electronic structure of benzyl-type carbanions and the corresponding organometallic compounds appears to be of great value in interpreting the dissociation behavior of the benzyl- and styrylalkali compounds (which are also included in the study).The resonance saturation phenomenon encountered in the quantum chemical and NMR study turns out to be an important factor in the dissociative behavior of p-CH3O compounds, as compared to the unsubstituted cases.The smaller dissociation costants of the o-CH3O compounds also parallel the results of the quantum chemical calculations, showing an additional interaction between the cation and the CH3O group.The weakening of the carbon-metal bond upon α-alkyl substitution parallels the increase of dissociation capability when alkyl or polymer chain substituents are present on the α-carbon atom.
Preparation of aryllithium compounds by metalation
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, (2008/06/13)
Process of metalating benzene containing alkyl, alkoxy or dialkylamino substituents, such as toluene, anisole and N,N-dimethyl-aniline, with an organolithium compound such as sec-butyllithium adducts with styrene, in the presence of a tertiary alkyl amine (containing no methyl groups) such as triethylamine, the ratio of lithium in said organolithium compound to the tertiary alkyl amine being 1 gram atom of the lithium to from about 0.25 to about 4 gram moles of the tertiary alkyl amine.
