1538-89-2Relevant academic research and scientific papers
Mechanistic Insight into the Photocontrolled Cationic Polymerization of Vinyl Ethers
Michaudel, Quentin,Chauviré, Timothée,Kottisch, Veronika,Supej, Michael J.,Stawiasz, Katherine J.,Shen, Luxi,Zipfel, Warren R.,Abru?a, Héctor D.,Freed, Jack H.,Fors, Brett P.
, p. 15530 - 15538 (2017)
The mechanism of the recently reported photocontrolled cationic polymerization of vinyl ethers was investigated using a variety of catalysts and chain-transfer agents (CTAs) as well as diverse spectroscopic and electrochemical analytical techniques. Our study revealed a complex activation step characterized by one-electron oxidation of the CTA. This oxidation is followed by mesolytic cleavage of the resulting radical cation species, which leads to the generation of a reactive cation - this species initiates the polymerization of the vinyl ether monomer - and a dithiocarbamate radical that is likely in equilibrium with the corresponding thiuram disulfide dimer. Reversible addition-fragmentation type degenerative chain transfer contributes to the narrow dispersities and control over chain growth observed under these conditions. Finally, the deactivation step is contingent upon the oxidation of the reduced photocatalyst by the dithiocarbamate radical concomitant with the production of a dithiocarbamate anion that caps the polymer chain end. The fine-tuning of the electronic properties and redox potentials of the photocatalyst in both the excited and the ground states is necessary to obtain a photocontrolled system rather than simply a photoinitiated system. The elucidation of the elementary steps of this process will aid the design of new catalytic systems and their real-world applications.
Living carbocationic polymerization of p-methoxystyrene using p-methoxystyrene hydrochloride/SnBr4 initiating system: Determination of the absolute rate constant of propagation for ion pairs
De, Priyadarsi,Faust, Rudolf
, p. 7930 - 7937 (2004)
The carbocationic polymerization of p-methoxystyrene (p-MeOSt)/SnBr 4 using p-Methoxystyrene hydrochloride was studied in CH 2Cl2 at ?30°C. The living polymerization was observed to be the first order in SnBr4 w
Towards reaction control using an ionic liquid: Biasing outcomes of reactions of benzyl halides
Keaveney, Sinead T.,Harper, Jason B.
, p. 15698 - 15704 (2013)
The effect of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide on substitution and elimination reactions of benzyl halides is examined and solvent control of the reaction outcome demonstrated. In competing reactions, the ionic liquid is shown to favour unimolecular processes over bimolecular processes and substitution over elimination, irrespective of the mole fraction of ionic liquid used. Temperature dependent analyses, where possible, are used to determine the microscopic origins of these effects.
Cu-Catalyzed Site-Selective Benzylic Chlorination Enabling Net C–H Coupling with Oxidatively Sensitive Nucleophiles
Lopez, Marco A.,Buss, Joshua A.,Stahl, Shannon S.
supporting information, p. 597 - 601 (2022/01/20)
Site-selective chlorination of benzylic C–H bonds is achieved using a CuICl/bis(oxazoline) catalyst with N-fluorobenzenesulfonimide as the oxidant and KCl as a chloride source. This method exhibits higher benzylic selectivity, relative to estab
Rapid, chemoselective and mild oxidation protocol for alcohols and ethers with recyclable N-chloro-N-(phenylsulfonyl)benzenesulfonamide
Badani, Purav,Chaturbhuj, Ganesh,Ganwir, Prerna,Misal, Balu,Palav, Amey
, (2021/06/03)
Chlorine is the 20th most abundant element on the earth compared to bromine, iodine, and fluorine, a sulfonimide reagent, N-chloro-N-(phenylsulfonyl)benzenesulfonamide (NCBSI) was identified as a mild and selective oxidant. Without activation, the reagent was proved to oxidize primary and secondary alcohols as well as their symmetrical and mixed ethers to corresponding aldehydes and ketones. With recoverable PS-TEMPO catalyst, selective oxidation over chlorination of primary and secondary alcohols and their ethers with electron-donating substituents was achieved. The reagent precursor of NCBSI was recovered quantitatively and can be reused for synthesizing NCBSI.
Chlorination of benzylic and allylic alcohols with trimethylsilyl chloride enhanced by natural sodium montmorillonite
Tandiary, Michael Andreas,Masui, Yoichi,Onaka, Makoto
, p. 2639 - 2643 (2015/01/09)
A new and practical method for the efficient chlorination of tertiary, secondary, and primary benzylic and allylic alcohols is described. The method is characterized by the formation of hydrogen chloride from trimethylsilyl chloride and trace water, the formation of a carbenium ion through the protonation of an alcohol and subsequent dehydration, and the chlorination of the carbenium ion. During the process, sodium ion-exchanged montmorillonite plays a crucial role in capturing the generated hydrogen chloride, stabilizing the carbenium intermediate as well as promoting the chlorination.
A remarkably efficient Markovnikov hydrochlorination of olefins and transformation of nitriles into imidates by use of AcCl and an alcohol
Yadav, Veejendra K.,Babu, K. Ganesh
, p. 452 - 456 (2007/10/03)
HCl generated by mixing AcCl with EtOH brings about Markovnikov hydrochlorination of olefins in excellent yields. The products are isolated in states of high purity simply by removal of the volatile components under reduced pressure. Further, nitriles are transformed into imidate hydrochlorides on similar treatment with AcCl and an alcohol. This procedure for nitrile-imidate transformation is much more efficient than that used previously, which involved continuous passing of HCl gas into the solution of a nitrile in a solvent such as Et2O or benzene and an alcohol until one equivalent had been absorbed. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
