4132-49-4Relevant articles and documents
Hydroperoxide method for the synthesis of p-tert-butylphenol
Frolov, A. S.,Korshunova, A. I.,Koshel’, G. N.,Kurganova, E. A.,Yarkina, E. M.
, p. 1951 - 1956 (2021/11/05)
The results of studies related to the development of a highly selective three-stage method for the synthesis of p-tert-butylphenol along with acetone are presented. The alkylation of isopropylbenzene with tert-butyl alcohol in the presence of concentrated sulfuric acid makes it possible to obtain only the para-isomer of tert-butylcumene. For the liquid-phase aerobic oxidation of p-tert-butylcumene in the presence of the phthalimide catalysts, the hydrocarbon conversion reaches 45% with a selectivity of hydroperoxide formation of 90–95%. The process of acid decomposition of p-tert-butylcumene hydroperoxide to p-tert-butylphenol and acetone was studied. Conditions providing the production of p-tert-butylphenol in a yield of 90% were found.
Catalytic protodeboronation of pinacol boronic esters: Formal anti-Markovnikov hydromethylation of alkenes
Clausen, Florian,Kischkewitz, Marvin,Bergander, Klaus,Studer, Armido
, p. 6210 - 6214 (2019/06/27)
Pinacol boronic esters are highly valuable building blocks in organic synthesis. In contrast to the many protocols available on the functionalizing deboronation of alkyl boronic esters, protodeboronation is not well developed. Herein we report catalytic protodeboronation of 1°, 2° and 3° alkyl boronic esters utilizing a radical approach. Paired with a Matteson-CH2-homologation, our protocol allows for formal anti-Markovnikov alkene hydromethylation, a valuable but unknown transformation. The hydromethylation sequence was applied to methoxy protected (-)-Δ8-THC and cholesterol. The protodeboronation was further used in the formal total synthesis of δ-(R)-coniceine and indolizidine 209B.
Facile Hydrogenolysis of C(sp3)–C(sp3) σ Bonds
Fillion, Eric,Beaton, Eric,Nguyen, Yen,Wilsily, Ashraf,Bondarenko, Ganna,Jacq, Jér?me
supporting information, p. 3422 - 3434 (2016/11/13)
The modification of benzylic quaternary, tertiary, and secondary carbon centers through palladium-catalyzed hydrogenolysis of C(sp3)–C(sp3) σ bonds is presented. When benzyl Meldrum's acid derivatives bearing quaternary benzylic centers are treated under mild hydrogenolysis conditions – palladium on carbon and atmospheric pressure of hydrogen – aromatics substituted with tertiary benzylic centers and Meldrum's acid are obtained with good to excellent yield. Analogously, substrates containing tertiary or secondary benzylic centers yield aromatics substituted with secondary benzylic centers or toluene derivatives, respectively. Furthermore, this strategy is used for the high yielding synthesis of diarylmethanes. The scope of the reductive dealkylation reaction is explored and the limitations with respect to steric and electronic factors are determined. A mechanistic analysis of the reaction is described that consisted of deuterium labelling experiments and hydrogenolysis of enantioenriched derivatives. The investigation shows that the C(sp3)–C(sp3) σ bond-cleaving events occur through a hybrid SN1/SN2 mechanism, in which the palladium center displaces a carbon-based leaving group, namely Meldrum's acid, with inversion of configuration, followed by reductive elimination of palladium to furnish a C?H bond. (Figure presented.).
Bimolecular formation of radicals by hydrogen transfer, 12: Transfer hydrogenation of p-substituted α-methylstyrenes and of 9-methylenefluorene as a criterion of mechanism
Friebolin, Heike,Roers, Rolf,Ebenhoch, Jochen,Gerst, Matthias,Ruechardt, Christoph
, p. 385 - 389 (2007/10/03)
The uncatalyzed transfer hydrogenation of substituted α-methylstyrenes with 9,10-dihydroanthracene (DHA), xanthene (XAN), or 9,10-dihydroacridine (DHAC) was studied mechanistically. The three hydrogen donors react at very similar rates and with similar activation parameters and with little discrimination between the various substituted styrenes. The kinetic isotope effects are also similar and the solvent effect is small. A hydrogen atom transfer mechanism (retrodisproportionation) is, therefore, preferred to a hydride transfer mechanism. This is supported by the very similar reactivity of the hydrogen transfer reaction of DHA and XAN with 9-methylenefluorene. The product yields in all reactions investigated in this project were >90%. VCH Verlagsgesellschaft mbH, 1997.
Transfer Hydrogenation of p-Substituted α-Methylstyrenes by 9,10-Dihydroanthracene
Gerst, Matthias,Ruechardt, Christoph
, p. 7733 - 7736 (2007/10/02)
The rate constants k2 of the uncatalyzed transfer hydrogenation of five p-substituted α-methylstyrenes 1a-e vary less then a factor 2 (300 deg C) which supports the proposed radical mechanism (scheme 2) and excludes hydride transfer as an alternative.
Efficient Synthesis and Resolution of trans-2-(1-Aryl-1-methylethyl)cyclohexanols; Practical Alternatives to 8-Phenylmenthol
Comins, Daniel L.,Salvador James M.
, p. 4656 - 4661 (2007/10/02)
A short synthesis and resolution of effective chiral auxiliaries of the 8-arylmenthol-type achieved using inexpensive materials, a recyclable lipase, and easily applied procedures that are amenable to large-scale preparation.A variety of isopropylarenes were α-metalated with n-butylithium/potassium tert-pentoxide and treated with cyclohexene oxide to provide racemic trans-2-(1-aryl-1-methylethyl)cyclohexanols 6a-f in fair to high yield.Candida rugosa lipase and lauric acid were used to resolve these racemic alcohols by converting the (-)-enantiomer to its laurateester.The enzymatic resolutions were carried out at 40 deg C and were faster in cyclohexane than in hexanes.The synthesis and resolution of racemic trans-2-(1-methyl-1-phenylethyl)cyclohexanol (6a) were performed on a 1 mol scale in 68 percent overall yield, requiring three steps for (+)-6a and five steps for (-)-6a.
Perfluorooctanesulfonic acid catalyzed Friedel-Crafts alkylation with alkyl halides
Fu,He,Lei,Luo
, p. 1273 - 1279 (2007/10/02)
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.
A General Olefin Synthesis
Wenkert, Ernest,Ferreira, Tamis W.
, p. 840 - 841 (2007/10/02)
The reaction between secondary Grignard reagents and alkylthioarenes or alkylthioalkenes in the presence of 1:1 nickel dichloride-triphenylphosphine causing the substitution of alkylthio-groups by hydrogen atoms, the nickel(0)-induced replacement of alkylthio-groups of the aforementioned sulfides by alkyl or aryl functions, and the observation of regiocontrol in the catalysed reactions of Grignard reagents with unsymmetrical 1,1-bis(alkylthio)alkenes have led to a scheme of general, regio-, and stereo-selective olefin synthesis.
Mechanisms of free-radical reactions. XI. Kinetic investigation of the free-radical chlorination of alkyl aromatic hydrocarbons by phenylchloroiodonium chloride
Dneprovskii, A. S.,Kasatochkin, A. N.
, p. 693 - 699 (2007/10/02)
The free-radical chlorination of meta- and para-substituted toluenes, ethylbenzene, and cumenes by phenylchloroiodonium chloride was investigated by the method of competing reactions.The good correlation between the relative reaction rate constants and the Brown ?+ constants and also the large negative values of ρ indicate separation of charges in the transition state.The values of the primary kinetic isotope effects of hydrogen decrease with increase in the reactivity of the substrate, whereas the values of the reaction parameters vary irregularly.The deviations from the inverse relation between the reactivity and the selectivity are due to the polar character of the transition state.
