- Effect of solvent on the lithium-bromine exchange of aryl bromides: Reactions of n-butyllithium and tert-butyllithium with 1-bromo-4-tert- butylbenzene at 0 °C
-
The outcome of reactions of 1-bromo-4-tert-butylbenzene (1), a representative aryl bromide, with n-BuLi or t-BuLi at 0 °C in a variety of solvent systems has been investigated. The products of reactions of 1 with n-BuLi vary significantly with changes in solvent composition: 1 does not react with n-BuLi in pure heptane; the exchange reaction to give (4-tert-butylphenyl) lithium, which is slow in pure diethyl ether, is virtually quantitative in heptane containing a small quantity of THF; and the reaction of 1 with n-BuLi in THF leads to considerable coupling. Lithium-bromine exchange is the virtually exclusive outcome of reactions of 1 with t-BuLi in every solvent studied except pure heptane: the presence of a small quantity of any of a variety of structurally diverse ethers (Et2O, THF, THP, MTBE) in the predominantly hydrocarbon medium affords (4-tert-butylphenyl)lithium, assayed as tert-butylbenzene, in yields exceeding 97%. The only side products observed from reactions of 1 with t-BuLi are small amounts of benzyne-derived hydrocarbons.
- Bailey, William F.,Luderer, Mark R.,Jordan, Kevin P.
-
-
Read Online
- Perfluorooctanesulfonic acid catalyzed Friedel-Crafts alkylation with alkyl halides
-
A new procedure to prepare superacid perfluorooctanesulfonic acid (POSA) is reported. POSA catalyzed Friedel-Crafts alkylation of aromatic compounds with alkyl halides in liquid-phase reactions. Alkylation gave higher total yields than the corresponding reactions with Nafion-H, without the need of any complex decomposition or work-up. The reactions do not need to be carried out under absolutely anhydrous condition. The catalyst POSA can be easily separated from the reaction mixture and reused or recovered. The reactivity of the alkylation reagents and the mechanism of the reaction are discussed.
- Fu,He,Lei,Luo
-
-
Read Online
- Determination of critical temperatures for mixtures of alkylbenzenes
-
The liquid-vapor critical temperatures of benzene mixtures with 1,3-di-tert-butylbenzene, 1,4-di-tert-butylbenzene, and 1,3,5-tri-tert- butylbenzene; a mixture of di-tert-butylbenzene isomers; and a toluene mixture with 3,5-di-tert-butyltoluene were determined over the entire range of composition by means of the amouule method. It was found that the excess critical temperature of the mixtures is related to the critical volumes of the substances. The capabilities of several calculation methods for predicting the critical temperature of mixtures were analyzed on the basis of published data and the obtained results. The Lee-Kesler rules of mixtures were refined by introducing binary interaction parameters.
- Nesterov,Nazmutdinov,Sarkisova,Nesterova,Vodenkova
-
-
Read Online
- Radical aromatic substitution with benzene chromiumtricarbonyl
-
Radical aromatic substitution of tert-butyl groups for hydrogen on simple arene chromiumtricarbonyl complexes was accomplished. Preexisting tert-butyl groups and methoxy groups directed incoming radicals primarily to the meta-position, and methoxy groups diminished the rate of substitution by roughly tenfold.
- Byers, Jeffrey H.,Neale, Nathan R.,Bradford Alexander,Gangemi, Stephen P.
-
-
Read Online
- Dual Nickel/Photoredox-Catalyzed Deaminative Cross-Coupling of Sterically Hindered Primary Amines
-
We report a method to activate α-3° amines for deaminative arylation via condensation with an electron-rich aldehyde and merge this reactivity with nickel metallaphotoredox to generate benzylic quaternary centers, a common motif in pharmaceuticals and natural products. The reaction is accelerated by added ammonium salts. Evidence is provided in support of two roles for the additive: inhibition of nickel black formation and acceleration of the overall reaction rate. We demonstrate a robust scope of amine and haloarene coupling partners and show an expedited synthesis of ALK2 inhibitors.
- Dorsheimer, Julia R.,Ashley, Melissa A.,Rovis, Tomislav
-
supporting information
p. 19294 - 19299
(2021/11/23)
-
- Carbon-based leaving group in substitution reactions: Functionalization of sp3-hybridized quaternary and tertiary benzylic carbon centers
-
Lewis acid promoted substitution reactions employing Meldrum's acid and 5-methyl Meldrum's acid as carbon-based leaving groups are described which transform unstrained quaternary and tertiary benzylic Csp 3-Csp3 bonds into Csp3-X bonds (X = C, H, N). Importantly, this reaction has a broad scope in terms of both suitable substrates and nucleophiles with good to excellent yields obtained (typically >90%).
- Mahoney, Stuart J.,Lou, Tiantong,Bondarenko, Ganna,Fillion, Eric
-
p. 3474 - 3477
(2012/09/05)
-
- Silylium-arene adducts: An experimental and theoretical study
-
The solvent-coordinated [Me3Si·arene][B(C 6F5)4] salts (arene = benzene, toluene, ethylbenzene, n-propylbenzene, isopropylbenzene, o-xylene, m-xylene, p-xylene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene) are prepared and fully characterized. As an interesting decomposition product the formation of bissilylated fluoronium ion [Me3Si-F-SiMe 3]+ was observed and even cocrystallized with [Me 3Si·arene][B(C6F5)4] (arene = benzene and toluene). Investigation of the degradation of [Me 3Si·arene][B(C6F5)4] reveals the formation of fluoronium salt [Me3Si-F-SiMe3][B(C 6F5)4], B(C6F5) 3, and a reactive "C6F4" species which could be trapped with CS2. Upon addition of CS2, the formation of a formal S-heterocyclic carbene adduct, C6F 4CS2-B(C6F5)3, was observed. The structure and bonding of substituted [Me3Si· arene][B(C6F5)4] with arene = R nC6H6-n (R = H, Me, Et, Pr, and Bu; n = 0-6) is discussed on the basis of experimental and theoretical data. X-ray data of [Me3Si·arene][B(C6F5)4] salts reveal nonplanar arene species with significant cation...anion interactions. As shown by different theoretical approaches (charge transfer, partial charges, trimethylsilyl affinity values) stabilizing inductive effects occur; however, the magnitude of such effects differs depending on the degree of substitution and the substitution pattern.
- Ibad, Muhammad Farooq,Langer, Peter,Schulz, Axel,Villinger, Alexander
-
supporting information; experimental part
p. 21016 - 21027
(2012/03/07)
-
- Alkylation of pyrocatechol in tert-butyl alcohol-sulfuric acid-benzene
-
Alkylation of pyrocatechol with tert-butyl alcohol in benzene in the presence of sulfuric acid gave 3,5-di-tert-butylbenzene-1,2-diol in a higher yield than in analogous reaction with tert-butyl alcohol. This result was rationalized by reduction of inhibitory effect of liberated water, formation of heterogeneous system, and occurrence of the alkylation process in nonpolar organic phase. Intermediate products were identified and found to undergo intra- and intermolecular tert-butyl group transfer with formation of more stable 3,5-di-tert-butylbenzene-1,2-diol. The formation of p-di-tert-butylbenzene indicated participation of benzene in crossalkylation processes. Pleiades Publishing, Ltd., 2011.
- Vol'eva,Prokof'eva,Belostotskaya,Komissarova,Gorbunov,Kurkovskaya
-
experimental part
p. 1310 - 1312
(2011/12/05)
-
- Nickel-catalyzed Kumada cross-coupling reactions of tertiary alkylmagnesium halides and aryl bromides/triflates
-
We report a Ni-catalyzed process for the cross-coupling of tertiary alkyl nucleophiles and aryl bromides. This process is extremely general for a wide range of electrophiles and generally occurs with a ratio of retention to isomerization >30:1. The same procedure also accommodates the use of aryl triflates, vinyl chlorides, and vinyl bromides as the electrophilic component.
- Joshi-Pangu, Amruta,Wang, Chao-Yuan,Biscoe, Mark R.
-
supporting information; experimental part
p. 8478 - 8481
(2011/06/25)
-
- Nickel-catalyzed cross-coupling of aryl bromides with tertiary grignard reagents utilizing donor-functionalized N-heterocyclic carbenes (NHCs)
-
Metal-catalyzed cross-coupling reactions are among the most important transformations in organic synthesis, allowing the efficient construction of complex structures from simpler, readily available building blocks.Many applications in large and small-scale synthesis can be found in different areas such as agrochemicals, pharmaceuticals and supramolecular chemistry. Whereas the coupling of sp2-hybridized carbon atoms in either reaction partner is well established, the use of CACHTUNGTRENUNG(sp3)-hybridized substrates presents some challenges. Catalytic cross-coupling of sterically hindered tertiary alkyl substrates is especially difficult, generally resulting in low yields, and thus, only few reports exist.[27] A big challenge in this field is not only to get the required level of reactivity, but also to overcome competing pathways like β-hydride elimination, hydrodehalogenation or isomerization
- Lohre, Claudia,Droege, Thomas,Wang, Congyang,Glorius, Frank
-
supporting information; experimental part
p. 6052 - 6055
(2011/06/25)
-
- Orthoamides, LIX [1]. Formyl-aalen [tris(diformylamino)methane] - A new formylating reagent for activated aromatic compounds
-
In the presence of strong Lewis acids such as aluminum chloride or boron trichloride, formyl-aalen [tris(diformylamino)methane] (3) acts as a formylating reagent for aromatic alkane compounds and aromatic ethers. The orthoamide 3 delivers three formyl groups for the formylation process. Thus toluene, cumene, tert-butylbenzene, hexylbenzene, o-xylene, p-cymene, biphenyl, anisole, diphenylether and 1,3-dimethoxybenzene can be formylated in 1,2-dichloroethane. In these reactions, 3 and aluminum chloride should be used in a molar ratio of 1:6 to 1:9.
- Kantlehner, Willi,Haug, Erwin,Scherr, Oliver,Ziegler, Georg
-
p. 1295 - 1304
(2007/10/03)
-
- Rhenium complexes-catalyzed alkylation of arenes with alkyl halides
-
Rhenium complexes have been shown to catalyze the alkylation of arenes with alkyl halides. When arenes were reacted with an alkyl chloride in the presence of a catalytic amount of rhenium complexes, such as bromopentacarbonylrhenium(I) [ReBr(CO)5], tricarbonylcyclopentadienylrhenium(I) [Re(C5H5)(CO)3] and decacarbonyldirhenium [Re2(CO)10], alkylation of the arenes proceeded under mild conditions to give a mixture of mono- and dialkyl substituted arenes in moderate-to-good yields.
- Nishiyama,Kakushou,Sonoda
-
p. 2779 - 2782
(2007/10/03)
-
- The Equilibria in the Interconversions of t-Butylbenzenes
-
The equilibra in the isomerisation and transalkylation of liquid t-butylbenzenes have been investigated in the temperature range 273 - 373 K.The thermodynamic characteristics of the rections have been determined and the enthalpies of formation (in the liquid state) of di- and tri-t-butylbenzenes have been calculated from the experimental and literature data.
- Nesterova, T. N.,Verevkin, S. P.,Karaseva, S. Ya.,Rozhnov, A. M.,Tsvetkov, V. F.
-
p. 297 - 298
(2007/10/02)
-
- Dienes as Possible Intermediates in the Catalytic Hydrogenation of Aromatic Hydrocarbons. 1. Dienes Derived from 1,4-Di-tert-butylbenzene and a Rhodium Catalyst
-
The evolution of the products upon hydrogenating three diene derivatives of 1,4-di-tert-butylbenzene (1) is compared with the formation of 1,4-di-tert-butylcyclohexene (2) and cis- and trans-1,4-di-tert-butylcyclohexane (3 and 4) from 1 on an alumina-supported rhodium catalyst to determine which diene (or dienes), upon adsorption on the catalyst, best represents the structure of the intermediate formed in the rate-determining surface reaction of 1.Of the dienes 1,4-di-tert-butyl-1,4-cyclohexadiene (6), 1,4-di-tert-butyl-1,3-cyclohexadiene (7), and 2,5-di-tert-butyl-1,3-cyclohexadiene (8), the last exhibits best the properties expected if it forms the same adsorbed intermediate as does 1 at the same hydrogen pressure.Unlike the arene, however, the dienes do not yield the cis-saturated isomer 3 as an initial product at low hydrogen pressures.Instead, cis-3,6-di-tert-butylcyclohexene (5) is formed along with ene 2 and arene 1; the dienes tend to exclude the cycloalkenes from the catalyst, their effectiveness increasing in the order 6 7 8.The result indicates that at low pressures little of arene 1 (less than 5percent) is transformed directly to cis-1,4-di-tert-butylcyclohexane (3); instead enes 2 and 5 are produced initially, and because the concentration of the intermediate adsorbed dienes remains low during the hydrogenation of the arene, cis ene 5 is rapidly converted to 3 in the presence of the arene.At high hydrogen pressures, the cis ane 3 is an initial hydrogenation product of the dienes as it is of 1.
- Outlaw, James F.,Cozort, James Ray,Garti, Nissim,Siegel, Samuel
-
p. 4186 - 4190
(2007/10/02)
-
- Bond Fixation in Annulenes. 14. Synthesis of and Bond Shifting Equilibrium between 1,4- and 1,6-Di-tert-butylcyclooctatetraenes
-
Photolysis of the Diels-Alder adduct of 3,6-di-tert-butyl-o-benzoquinone and cyclobutadiene at ice-bath temperatures afforded the bicyclooctatriene 12.During warming to room temperature, this hydrocarbon underwent kinetically first-order valence isomerization to provide 5 and its bond shift isomer 4.This finding adumbrated the facility with which 4 and 5 are interconverted.Reaction of this cyclooctatetraene mixture with N-methyltriazolinedione gave urazoles 16 and 17 as chromatographically separable entities.Like 13, the related cycloadduct of 12 wherein both bridgehead tert-butyl groups exhibit restricted rotation , the angular tert-butyl substituent in 17 is sterically perturbed.Hydrolysis-oxidation of either 16 or 17 returned only mixtures of 4 and 5 because of their rapid bond shifting rates.When the equilibrium constant between these two isomers was determined by 1H NMR spectroscopy, it was found that 5, the apparently more congested compound, was the more stable in CDCl3 solution.The possible underlying causes of this phenomenon are discussed.
- Paquette, Leo A.,Hefferon, George J.,Samodral, Rodney,Hanzawa, Yuji
-
p. 1262 - 1266
(2007/10/02)
-
- Picosecond Laser Photolysis Studies of Hydrogen Atom Transfer Reaction via Heteroexcimer State in Pyrene-Primary and Pirene-Secondary Aromatic Amine Systems: Role of "Hydrogen-Bonding" Interaction between Amino Group of Donor and ? Electron Acceptor in the Heteroexcimer
-
The mechanism of charge transfer followed by proton transfer in the hydrogen atom transfer reaction of excited pyrene-primary and -secondary amine systems has been directly demonstrated by means of a picosecond laser photolysis method.In the case of pyrene-N-ethylamine heteroexcimer system in hexane, for example, it has been observed that the 1-hydro-1-pyrenyl radical and the pyrene triplet state are produced simultaneously in the time region of subnanosecond to nanosecond.The deuteration of the NH group of the amine affects considerably the rate of formation of the 1-hydro-1-pyrenyl radical but not the rate of intersystem crossing from the heteroexcimer.On the basis of the results obtained for various pyrene-primary and -secondary aromatic amine heteroexcimer systems, the nature of the interaction between donor and acceptor in these heteroexcimers and their conformation in relation to the mechanism of the hydrogen atom transfer reaction via heteroexcimer have been elucidated.
- Okada, Tadashi,Karaki, Ichiro,Mataga, Noboru
-
p. 7191 - 7195
(2007/10/02)
-