- Thioether-Mediated Degenerative Chain-Transfer Cationic Polymerization: A Simple Metal-Free System for Living Cationic Polymerization
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Cationic degenerative chain-transfer polymerization of vinyl ethers and p-alkoxystyrenes was investigated using a series of thioethers as a reversible chain-transfer agent via the equilibrium between a growing carbocationic species and the resulting sulfonium intermediate in the presence of a small amount of triflic acid (TfOH) as a cationogen. The stable thioether, which was easily prepared from isobutyl vinyl ether (IBVE) and n-butanethiol, efficiently controls the molecular weight of the resulting poly(IBVE) up to Mn ~ 1 × 105 with narrow molecular weight distributions (MWDs) (Mw/Mn ~ 1.2). Upon increasing the bulkiness of the alkyl substituents in the thiols (R-SH; R: n-Bu 2=CHOR′, R′: ethyl isobutyl cyclohexyl), the MWDs became broader due to the slower formation of the sulfonium intermediate for the degenerative chain-transfer reaction. For p-methoxystyrene, thioethers derived from bulkier alkylthiols or more electron-rich thiophenols are more effective. A silyl-protected difunctional dithioether produced telechelic polymers possessing hydroxyl groups at both chain ends and stable thiol linkers in the middle of the polymer chains. These polymers were subsequently used in chain-extension reactions in conjunction with diisocyanates and diols as chain extenders to be converted into high molecular weight polymers linked via urethane linkages. (Figure Presented).
- Uchiyama, Mineto,Satoh, Kotaro,Kamigaito, Masami
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- Composite herbicide based on spermine ammonium phosphate and sulfadiazole
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The invention discloses a composite herbicide based on diammonium phosphate and sulphone, and belongs to the technical field of herbicides. The composite herbicide comprises the following raw materials in percentage by weight 1 - 50%. The sulfonamide 1 -
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Paragraph 0054-0055; 0063-0064; 0073-0074; 0083
(2021/08/25)
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- Stereoselective synthesis and reactions of secondary alkyllithium reagents functionalized at the 3-position
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Secondary alkyllithium reagents bearing an OTBS group (TBS = tert-butyldimethylsilyl) at the 3-position can be prepared stereoconvergently through an I/Li exchange from a diastereomeric mixture of the corresponding secondary alkyl iodides. These lithium reagents react with a range of electrophiles, including carbon electrophiles, with retention of configuration to yield various 1,3-difunctionalized derivatives with good diastereoselectivities. Kinetic studies show that the 3- siloxy group strongly accelerates the epimerization at the lithium-substituted carbon atom. This method offers a new way to construct chiral open-chain molecules with excellent stereoselectivity.
- Moriya, Kohei,Didier, Dorian,Simon, Meike,Hammann, Jeffrey M.,Berionni, Guillaume,Karaghiosoff, Konstantin,Zipse, Hendrik,Mayr, Herbert,Knochel, Paul
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supporting information
p. 2754 - 2757
(2015/03/04)
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- Organocatalyzed anodic oxidation of aldehydes to thioesters
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A method has been developed for the direct conversion of aldehydes to thioesters via integration of organocatalysis and electrosynthesis. The thiazolium precatalyst was found to facilitate oxidation of thiolate anions, leading to deleterious formation of disulfide byproducts. By circumventing this competing reaction, thioesters were obtained in good-to-excellent yields for a broad range of aldehyde and thiol substrates. This approach provides an atom-efficient thioesterification that circumvents the need for stoichiometric exogenous oxidants, high cell potentials, or redox mediators.
- Ogawa, Kelli A.,Boydston, Andrew J.
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supporting information
p. 1928 - 1931
(2014/05/06)
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- Standard enthalpies of formation of Li, Na, K, and Cs thiolates
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The standard enthalpies of formation of alkaline metals thiolates in the crystalline state were determined by reaction-solution calorimetry. The obtained results at 298.15 K were as follows: δfH°m(MSR, cr)/kJ mol-1 = -259.0 ± 1.6 (LiSC2H5), -199.9 ± 1.8 (NaSC2H5), -254.9 ± 2.4 (NaSC4H9), -240.6 ± 1.9 (KSC2H 5), -235.8 ± 2.0 (CsSC2H5). These results where compared with the literature values for the corresponding alkoxides and together with values for δfH° m(MSR, cr) were used to derive a consistent set of lattice energies for MSR compounds based on the Kapustinskii equation. This allows the estimation of the enthalpy of formation for some non-measured thiolates.
- Leal, Joao P.
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experimental part
p. 441 - 446
(2010/08/04)
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- SYNTHESIS OF MONO(ALKYLTHIO)-SUBSTITUTED KETONES
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In the reaction of 2-propanone in the presence of sodium bicarbonate with a mixture of formaldehyde and the corresponding alkaline hydrolyzates of S-alkylthiuronium salts (thioalcoholates) β-keto sulfides (1-alkylthio-3-butanones) were obtained.Ketalization of the products with glycerol gave the cyclic derivatives alkylthio-1,3-dioxolanes.
- Sabirov, S. S.,Gnevasheva, L. M.,Ismailov, M. I.,Isobaev, M. D.
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p. 1239 - 1243
(2007/10/02)
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