959-42-2Relevant academic research and scientific papers
Cobalt-Catalyzed Silylcarbonylation of Unactivated Secondary Alkyl Tosylates at Low Pressure
Roque Pena, Joan E.,Alexanian, Erik J.
supporting information, p. 4413 - 4415 (2017/09/11)
A catalytic preparation of silyl enol ethers from unactivated secondary alkyl tosylates is reported. An inexpensive cobalt catalyst is used under mild conditions with low pressures of carbon monoxide. Nucleophilic, anionic cobalt carbonyls facilitate the catalytic activation of a range of alkyl tosylates. The silylcarbonylation offers a practical approach to synthetically valuable silyl enol ethers from simple starting materials.
Detailed Characterization of p-Toluenesulfonic Acid Monohydrate as a Convenient, Recoverable, Safe, and Selective Catalyst for Alkylation of the Aromatic Nucleus
Mahindaratne, Mathew P. D.,Wimalasena, Kandatege
, p. 2858 - 2866 (2007/10/03)
Alkylation of the aromatic nucleus, an important reaction in industry and synthetic organic chemistry, has traditionally been carried out by the well-known Friedel-Crafts reaction employing Lewis acid catalysts such as AlCl3 and BF3 or by using highly reactive organometallic reagents. Although protic acids such as anhydrous HF and concentrated H2SO4 have also been used in the alkylation of the aromatic nucleus, the notoriously corrosive, highly toxic, and hazardous nature of these agents has precluded their common use under ordinary laboratory conditions. Various organic sulfonic acids have, on occasion, been used as catalysts in Friedel-Crafts alkylations, but to our knowledge the chemistry and the scope of these reactions for common laboratory use have never been exploited in detail. In the present study we have characterized commercially available p-toluenesulfonic acid monohydrate (TsOH) as an efficient catalyst for the intermolecular coupling of the aromatic nucleus with activated alkyl halides, alkenes, or tosylates under mild conditions in an open atmosphere. In comparison to conventional Friedel-Crafts catalysts such as AlCl3, BF3, HF, and concentrated H2SO4, the extent of the formation of undesired products from side reactions such as transalkylation, polymerization, etc. was minimal with the TsOH-catalyzed reaction. The ability to recover and reuse the catalyst from the reaction mixtures, minimal generation of environmentally unfriendly waste, high specificity of the reaction, and the low cost of the catalyst are important advantages of the TsOH catalyst over the other conventional Friedel-Crafts catalysts.
Nucleophilic substitution reactions of 2-norbornyl arenesulfonates with anilines
Oh, Hyuck Keun,Joung, Eun-Mi,Cho, In Ho,Park, Young Sook,Lee, Ikchoon
, p. 2027 - 2038 (2007/10/03)
The kinetics and mechanism of the nucleophilic substitution reactions of exo- and endo-2-norbornyl arenesulfonates with anilines are investigated in methanol and acetonitrile at 60.0°C. Rate constants for three distinct competing processes, solvolysis ks
Norpinyl-Norbornyl Rearrangements: Destabilized 2-Norpinyl Cations
Fendel, Wolfgang,Kautz, Cornelia Brigitte,Kirmse, Wolfgang,Klar, Matthias,Siegfried, Rainer,Wonner, Aribert
, p. 1735 - 1744 (2007/10/03)
In order to explore the effect of electron-withdrawing substituents on 2-norpinyl (bicyclohept-2-yl) -> 2-norbornyl (bicyclohept-2-yl) rearrangements, cyano and pentafluoroethyl groups were introduced into the α and β (= bridgehead) positions.The substrates were synthesized from norpinan-2-one (8) by addition of HCN or C2H5Li, from 2-aminonorbornane-2-carbonitrile (25) by rearrangement, and from 1-(pentafluoroethyl)bicyclohexan-2-one (51) by ring expansion.Arenesulfonates and diazonium ions were used to generate the 2-norpinyl cations. - Electron acceptors in the α position of 2-norpinyl substrates promote the norpinyl -> norbornyl rearrangement.Internal return of the counterion leads to endo-2-norbornyl sulfonates, often without formation of the analogous alcohols, i.e., the destabilized norpinyl cations do not escape from tight ion pairs.Electron acceptors in the β (bridgehead) position favor displacement and elimination processes with retention of the norpinyl structure while the norpinyl -> norbornyl rearrangement is inhibited, more strongly by β-C2F5 than by β-CN.The tendency to separate the positive charge from the electron acceptor explains the divergent effects of α and β substitution. - The kH/kα-CN and kH/kβ-CN rate ratios in the 2-norpinyl and 2-norbornyl series are virtually the same, and the stereoselectivity of the intervening carbocations is not significantly affected by electron-withdrawing substituents. - Keywords: 1,2-Alkyl shifts / Ring expansion / Destabilized carbocations / Stereoselectivity / ? Delocalization
Stereochemistry of Base-Promoted 1,2-Elimination from exo-2-Bicycloheptyl Tosylate and Chloride
Bartsch, Richard A.,Lee, Jong Gun
, p. 212 - 217 (2007/10/02)
Elimination reactions of exo-2-bicycloheptyl tosylate and chloride and their exo-3-deuterated analogues are studied in base-solvent systems that induce clean bimolecular 1,2-eliminations.Their relative propensities for competitive syn-exo and anti-endo-H elimination modes are assessed from nonkinetically determined deuterium isotope effects and the deuterium content in the bicyclohept-2-ene formed from the deuterated substrates.The competition between syn-exo and anti-endo-H elimination is influenced by base association, which stabilizes the synelimination transition state.Potential steric hindrance by oversized dissociated bases has no effect on the elimination stereochemistry.
Application of Mechanistic and Transition-State Indicators to endo and exo-2-Norbornyl Arenesulfonates. Definition of a new Mechanistic Indicator
McManus, Samuel P.,Smith, Maurice R.,Shankweiler, Jean M.,Hoffman, Robert V.
, p. 141 - 148 (2007/10/02)
We have mechanistically classified endo- and exo-2-norbornyl arenesulfonates by using two common probes: the effect on rate of added thiourea and rate correlation in aqueous ethanol and trifluoroethanol.Interestingly, the exo isomer is improperly classified by each of these probes because of medium-dependent ion-pair return.In search of better mechanistic indicators, pseudo-first-order solvolytic rates and products have been determined for a series of endo- and exo-2-norbornyl arenesulfonates.Using these and literature data, we have compared these substrates with others by plotting α-deuterium isotope effects against β1gMe values determined for a series or arenesulfonates in the same or a similar solvent.The use of this type of plot as a heuristic method for distinguishing k8 and kΔ substrates is discussed.Finally, our product studies are consistent with the involvement of solvent-seperated ion pairs in the solvolysis of 2-norbornyl arenesulfonates.Different alcohol-ether product ratios for the isomeric esters in consistent with dual pathways for product formation with the endo substrates.
Solvent Effects on Solvolytic Reactivity. A Diagnostic Test for Neighboring-Group Assistance by ? Conjugation in Solvolysis Reactions
Roberts, Donald D.
, p. 2521 - 2526 (2007/10/02)
The solvolysis rates of 13 arenesulfonates have been determined in mixtures of ethanol and water (the E-series solvents) and acetic acid and formic acid (the A-series solvents).The substrates studied include the following: neophyl (1), 2-adamantyl (2), neopentyl (3), and cyclooctyl (4) tosylates; cyclopropylcarbinyl pemsylate (5a) and tosylate (5b); exo-2-norbornyl tosylate (6); cyclobutylcarbinyl (7), cyclobutyl (8), and pinacolyl (9) brosylates; cyclopentyl (10), cyclohexyl (11), and 2-propyl (12) tosylates; and cyclopentylcarbinyl brosylate (13).Correlations of the rate data by eq 1 t(Y) = a + b log kt(neophyl-OTs)> showed that the various substrates responded differently to the examined solvent effects on the solvolytic reactivity.For compounds 2-4, linear correlations were obtained.For compounds 5-9, E-line, A-line dispersions were noted which diverged with increasing ionizing power; for compounds 10-12, parallel E-line, A-line dispersions were obtained; and for compound 13, an E-line, A-line dispersion was observed which converged with increasing ionizing power.Stastistical analyses of the rate data correlations confirmed the significance of the E or A classification of data.The results are interpreted in terms of differences in the involvement of solvent in the transition state for those solvolyses assisted by bridging from those assisted by C-C ? bond hyperconjugation.
