Synthesis and characterization of fluorinated PEO-b-PDMS-b-fluorinated PEO by free radical addition

Fluorinated poly（ethylene oxide） propyl-b-polydimethylsiloxane-b-propyl fluorinated poly（ethylene oxide） （FPEO-b-PDMS-b- FPEO） was synthesized by a free radical addition of carbon-hydrogen of polyether segments of poly（ethylene oxide） propyl-b- polydimethylsiloxane-b-propyl poty（ethylene oxide） （PEO-b-PDMS-b-PEO） to hexafluoropropylene （HFP） using tert-butyl peroxypivalate as an initiator. In order to reduce the possibility of side reaction, the protection and deprotection via silylation were used for the end-hydroxyls in PEO-b-PDMS-b-PEO chain. The structure of Intermediates and FPEO-b-PDMS-b-FPEO was confirmed by means of Fourier transform infrared and 1H NMR spectroscopy. The effects of amount of initiator, reaction temperature and time on free radical addition were investigated in detail. 2009 Xing Yuan Zhang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Electrochemical Atom Transfer Radical Addition of Polychloroalkanes to Olefins Promoted by 4,4-Di-tert-butyl Bipyridine

A new electrochemical strategy for the atom transfer radical addition(ATRA)of polychloroalkanes across olefins has been realized by the synergism of paired electrolysis and halogen bonding activation.Notably,readily accessible 4,4-di-tert-butyl bipyridine(dtbpy),acting as a halogen bonding acceptor,shifted the reduction potential of C—Cl bonds positively by 110 mV.The decreased operating potential leads to a wide substrate scope and excellent functional group compatibility.A diverse array of terminal and internal alkenes such as(hetero)aryl olefins,unactive aliphatic olefins,and natural products and drugs-derived olefins were well compatible.

Radical Addition of Perfluorinated Alkyl Iodides to Multi- Layered Graphene and Single-Walled Carbon Nanotubes

A simple one-pot reaction that serves to functionalize graphite nanosheets(graphene)and single-walled carbon nanotubes(SWNTs)with perfluorinated alkyl groups is reported.Free radical addition of 1-iodo-1H,1H,2H,2H-perfluorododecane to ortho-dichlorobenzene suspensions of the carbon nanomaterial is initiated by thermal decomposition of benzoyl peroxide.Similarly,UV photolysis of 1-iodo-perfluorodecane serves to functionalize the carbon materials.Perfluorododecyl-SWNTs,perfluorododecyl-graphene,and perfluorodecyl-graphene are characterized by infrared(IR)and Raman spectroscopy,X-ray photoelectron spectroscopy(XPS),thermogravimetric analysis(TGA),and atomic force microscopy(AFM).The products show enhanced dispersability in CHCl3 as compared to unfunctionalized starting materials.The advantage of this one-pot functionalization procedure lies in the use of pristine graphite as starting material thereby avoiding the use of harsh oxidizing conditions.

Studies on polyhaloalkanes Ⅰ.Radical addition of polyfluoroalkyl iodides to diethyl allylphosphonate

Radical addition of polyfluoroalkyl iodides to the C=C double bond of diethyl allylphos- phonate was carried out in CH_2Cl_2-H_2O two-phase medium in the presence of sodium dithionite to give dicthyl 3-polyfluoroalkyl-2-iodopropylphosphonates(3)in excellent yields.Compounds 3 were then converted to diethyl polyfluoroalkanephosphonates(4)by zinc-reduction,Thus a facile method for preparing polyfluoroalkanephosphonates is realized.

The reaction of perfluoroalkanesulfinatesIV.Perfluoroalkyl radical addition to olefins initiated by single electron oxidation of perfluoroalkanesulfinate

Sodium perfluoroalkanesulfinates [Cl(CF_2)n SO_2 Na (1), a, n=4; b, n=6; c, n=8] with the reduction potentials about 0.95-1.00V could be oxidized readily with various oxidizing agents such as Mn (OAc)_3·2H_2O, Ce(SO_4)_2, HgSO_4 and Co_2O_3 to generate perfluoroalkyl radicals which added to the olefins RCH=CHR′to give two kinds of adducts, namely RCH (R_f) CHXR′(3, X=H; 4, X=OAc), with good yields depending upon the solvent system used. Different oxidizing agents showed slight variation on the yields of the adducts. The reaction time could be greatly shortened at higher temperature. Thus, this reaction provides a new way for introducing a perfluoroalkyl group into olefinic compounds.

Asymmetric radical allylation of β-keto esters with vinyl cyclopropanes by dual photoredox/nickel catalysis

Radical-involved allylation reactions have emerged as a powerful platform for construction of carbon-carbon and carbonheteroatom bonds, facilitating the strategic incorporation of diverse allyl moieties. Nevertheless, this burgeoning field still faces ongoing challenges, including limitations of radical precursors and coupling partners, and difficulties in achieving enantiocontrol. Herein, we report for the first time a highly enantioselective radical allylation involving β-keto esters with vinyl cyclopropanes utilizing a synergistic dual photoredox/nickel catalysis under visible light irradiation. The mild and redox-neutral catalytic protocol demonstrates an extensive substrate compatibility and good functional tolerance, providing access to enantioenriched β-keto esters featuring quaternary α-stereocenter with good yields and high enantioselectivities. Preliminary mechanistic studies have uncovered that the success of the reaction hinges on the dual roles of nickel catalyst, including in situ formation of photoredox sensitive substrate/Ni complex and the ensuing asymmetric radical addition step.

Dialkyl phosphinic acids:Synthesis and applications as extractant for nickel and cobalt separation

Three kinds of dialkylphosphinic acids(DAPAs),i.e.dihexylphophinic acid(DHPA),di-(2,4,4-trimethylpentyl) phosphinic acid(DTMPPA)and didecylphophinic acid(DDPA),were synthesized through free radical addition reaction.The influence of the types of initiator,reation time and reaction temperature on the yield of DAPAs were investigated.The products were characterized by NMR and MS.By using DHPA,DTMPPA and DDPA(10%in kerosene)as extractants,the extraction of Co2 +and Ni2 +in sulphate medium at different equilibrium pH values were measured.The results show that the maximum yield of DHPA, DTMPPA and DDPA can all be achieved at about 130℃under the initiation of di-tert-butyl peroxide(DTBP).All the extraction of cobalt with respect to DHPA,DDPA and DTMPPA precedes that of nickel.The difference in pH1/2 value(defined as the pH at which 50%metal extraction occurs)between cobalt and nickel increases in the following sequence from large to small:DHPA,DDPA and DTMPPA,which indicates that the separation ability for cobalt and nickel ascends from DHPA,DDPA to DTMPPA.

Synthesis of core-shell structured polymers with inserted thioether from a multi-functional scaffold

The synthesis of a thioether inserted, core-shell structured polymer from the scaffold of hyperbranched polyglycerol (PG) was described. PG was first allyl functionalized, and in the presence of AlBN, the allyl groups further underwent radical addition to thiol compounds, thus thiol functional polyethylene oxide monomether (MPEO) were grafted onto PG. Similarly, 2-mercaptoethylammonium chloride was introduced onto PG via thiol addition, and the residual amino groups were further quaternized with decyl bromide, leading to an amphiphilic core-shell structure polymer. (c) 2007 De Cheng Wan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

MODIFICATION OF NYLON-6 WITH POLYORGANOSILOXANE

Nylon-6 has been modified by polyorganosiloxane. It was realized by radical addition of caprolactam to the vinyl group of silicone and anionic polymerization of the monomer in the presence of the silicone macromer. The mechanical properties of the modified plastics are not far from that of the unmodified one whereas its frictional properties are significantly improved.

A Modular Representation of K-root-and Jacobson Structure Theorems for Additive Categories

In this paper,we give definition and moduler representation of Kothe root for additive cate gories.Using these results,get inner representation of J-root and fully homomorph class of Jscmisimple additive categories.

Direct synthesis of unnatural amino acids and modifications of peptides via LADA strategy

Unnatural amino acids(UAAs)have broad applications in pharmaceutical sciences and biological studies.Current synthetic methods for UAAs mainly rely on asymmetric catalysis and often require several steps.There is a lack of direct and simple methods.To address this challenge,we designed the LADA(labeling-activation-desulfurization-addition)strategy:selective labeling and activation of cysteine residues,the photocatalytic desulfurization and the subsequent radical addition to alkenes.Although composed of two steps,it is one-pot synthesis and has advantages such as high functional group tolerance,biocompatible reaction condition,and retained stereochemistry.This highly efficient strategy was successfully applied in the direct synthesis of unnatural amino acids and modifications of peptides with more than 50 examples.

LADA strategy for the synthesis of unnatural amino acids and direct modifications of peptides

Unnatural amino acids(UAAs)are important building blocks in organic synthesis and drug discovery.They are also frequently integrated into peptides or proteins for biological studies.However,the direct and simplified synthesis of UAAs remains a great challenge.At the same time,vast known peptide modifications are based on carbon-heteroatom bonds.There are no general methods for peptide modifications via the construction of C–C bonds.To address this challenge,herein we propose the LADA strategy,which is composed of two steps:the selective labeling and activation of cysteine residues,the desulfurization to generate carbon-centered radical and the radical addition to alkenes to build C–C bond.This one-pot protocol has obvious advantages such as good functional group tolerance,biocompatible reaction conditions,and retained stereochemistry.This strategy was successfully utilized for the synthesis of unnatural amino acids and direct modifications of peptides.