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.

Stereoselective Functionalization at C-2 and C-3 of the Gibberellin via an Intramolecular Free Radical Cyclization Approach

Stereoselective functionalization at C-2 and C-3 of the gibberellin skeleton was achieved via an intramolecular free radical cyclization approach using a tethered C-19 halomethyl ester as the radical precursor.

Computational Study of the Cyclization of 5-Hexenyl, 3-Oxa-5-Hexenyl and 4-Oxa-5-Hexenyl Radicals

The intramolecular cyclization of 5-hexenyl radicals continues to be an important synthetic method for the construction of five-membered rings. The synthetic utility arises from the high degree of regioselectivity to give predominantly cyclopentyl products in high yield under mild conditions. Recently we reported product cyclization studies on 4-oxa perturbed 5-hexenyl radical. In this paper, we report our results from a computational study (UB3LYP and UCCSD (T)) of the cyclization of a series of 5-hexenyl and 3-and 4-oxa-5-hexenyl radicals. Three highly conserved cyclization tran-sitions states (exo-chair, exo-boat and endo-chair) were located for 10 acyclic radicals. Activation energies were calcu-lated for the three modes of cyclization for each radical. Calculated values for the exo/endo cyclization ratios had a high level of agreement with experiment and predictions were offered for two cases that have not been experimentally tested. The increased percentage of exo-cyclization with 3-and 4-oxa substitution is the result of an increase in the energy dif-ference between the exo-and endo-chair transition states compared to the hydrocarbon systems. The decreased rate of cyclization of the 4-oxa compounds is primarily due to the stabilization of the initial acyclic radical by the vinyl ether linkage. The increase in the rate of cyclization with 3-methyl substitution is due to the increased conformational energy of the starting acyclic radical.

A FACILE APPROACH FOR THE SURFACE MODIFICATION OF POLY(VINYLIDENE FLUORIDE) MEMBRANE VIA SURFACE-INITIATED ATOM TRANSFER RADICAL POLYMERIZATION

A novel approach for the surface modification of poly(vinylidene fluoride)(PVDF)membrane was successfully realized through alkaline treatment,UV-induced bromine addition,and followed by surface-initiated atom transfer radical polymerization(ATRP)of methyl methacrylate(MMA).Chemical changes on the PVDF membrane before and after modification were analyzed with attenuated total reflectance Fourier transform infrared spectroscopy(ATR/FT-IR)and X-ray photoelectron spectroscopy(XPS).Primary kinetic study revealed...

“Anti-Michael” and Michael Additions in the Reactions of 2-Arylmethyliden-1,3-Indandiones with 2-Aminothiophenol

A novel 2-indano[2,3b]-2-ferrocenyl- and 2-indano[2,3b]-2-(p-methoxy-phenyl)[1,5]benzo-2,5-dihydrothiazepine 5a,b (addition Michael/cyclization) (~30.32%), indano[2,3b]-2-ferrocenyl- and 2-(p-methoxyphenyl)[1,4] benzothiazine 4a,b (addition “anti-Michael”/cyclization) (~45.43%), respectively, were obtained by the condensation of 2-ferrocenyl-and 2-(p-methoxy-phenyl)methyliden-1,3-indandiones 1a,b with o-aminothiophenol 2 in the presence of AcOH and HCl. A new “anti-Michael” addition reaction of 1,4-bis-heteronucleophile 2 into 2-arylmethyliden-1,3-indandiones was reported. As a result of this reaction the product 1a,b was obtained. The structures of the resultant compounds were elucidated by IR, 1H and 13C NMR spectroscopy, mass spectrometry, elemental and X-ray diffraction analysis. The in vitro antitumor activity of the obtained products was researched using the following human cancer cell lines: glioblastoma (CNS U-251), prostatic adenocarcinoma (PC-3), chronic myelogenous leukemia (K562), colorectal adenocarcinoma (HCT-15), mammary adenocarcinoma (MCF-7), and small cell lung cancer (SKLU) and the sulforhodamine B (SRB) method. Among these new compounds some thiazine and thiazepine derivatives showed compelling in vitro antitumor effects on cell lines K-562, HCT-15, SKLU-1 and MCF-7.

The Addition Reaction of p-Chlorobenzaldoxime Dehydrodimer with 1,3-Dienes

The addition reaction of p chlorobenzaldoxime dehydrodimer and 1,3 dienes in refluxing chloroform gives linear 1,4 addition products. The reaction is probably a free radical process.

Radical denitrogenative transformations of polynitrogen heterocycles:Building C–N bonds and beyond

Polynitrogen heterocycles are readily available and have recently arisen as versatile synthons for the formation of various C-C and C-X bonds,and medicinally active nitrogen-containing heterocycles.Several cascade reactions,including annulation,radical cascade,and borylation reactions,have been reported in which polynitrogen heterocycles are applied as arylation reagents.The success of these exceptional reactions illustrates the great synthetic potential of polynitrogen heterocycles,which provides a direct and useful approach to arylation reactions and the synthesis of nitrogen-containing heterocycles.The use of photocatalysts to effectively transfer energy from visible light to non-absorbing compounds has gained increasing attention as this method allows for the mild and efficient generation of radicals in a controlled manner.This approach has thus led to new methods that involve unique bond formation reactions.In addition,the use of free radical intermediates stabilized by transition metal catalysts is a powerful way to construct new chemical bonds.The aim of this review is to highlight the rapidly expanding area of radical-initiated denitrogenative cascade reactions of polynitrogen heterocycles and elaborate on their mechanisms from a new perspective by using photocatalysis and metal-based catalysis.

Planar Blatter radicals through Bu_(3)SnH-and TMS_(3)SiH-assisted cyclization of aryl iodides: azaphilic radical addition

Bu_(3)SnH-and TMS_(3)SiH-assisted cyclizations of iodoarene derivatives of benzo[e][1,2,4]triazine lead to the formation of planar Blatter radicals(2-phenyl-3H-[1,2,4]triazino[5,6,1-kl]phenoxazin-3-yls and 2-phenyl-3H-[1,2,4]triazino[5,6,1-kl]phenothiazin-3-yls)in yields of up to 96%.

Radicals as Chiral Catalysts for Asymmetric Radical Cyclization Reactions

Due to the innate highly reactive properties and short life-time,organic free radicals can often serve as promoters or intermediates to engage in various radical transformations,which are often otherwise difficult to access by ionic pathway-based mechanisms.With the evolvement of radical chemistry,chiral radical catalyzed-transformations have recently emerged as an attractive and robust platform for synthesis of chiral molecules of interest.Herein,we highlight several creative and strategic advances in chiral radical catalyst design,cyclization reaction achievements,and future challenges.

Photocatalytic Site-Selective Cascade Radical Addition of Biaryl Ynones for the Construction of Spiro-and Fused Carbon Rings

Functionalized free radical addition/cyclization reactions represent an efficient way for introducing new functionality or coupling fragments to molecules.Ynones are good regional selectivity radical acceptors in organic synthesis,and many of bio-relevant cyclic compounds could be easily obtained by direct radical cyclization reaction.Here,we report a photocatalytic cascade radical addition of biaryl ynones,for the divergent synthesis of privileged carbon cycles.Additionally,further transformation of the multi-functional group product into a variety of other derivatives demonstrates the synthetic value of this developed method.

Synthetic Studies toward Pseudolaric Acids:Radical Cyclization to Form Bridged Scaffold

Pseudolaric acids are a family of diterpenoid natural products that exhibit a broad spectrum of biological activities.The main structural feature of their framework is a trans-fused perhydroazulene bearing a bridged lactone positioned at the junction of the rings.Herein,we have developed a radical cyclization strategy that allows flexible tuning of the cyclization process through diverse silicon substitutions on the substrates.This strategy can assist in constructing a series of skeletons with structural resemblance to pseudolaric acids and expedites the construction of the bridged lactone.Finally,it facilitates the synthesis of the entire skeletal structure of the pseudolaric acidfamily of natural products,excludingthe B-ringfunctionalization.

Metal-and light-free approach to polyheterocycles via a quinone-Cs_(2)CO_(3)couple promoted regioselective cascade radical cyclization

A highly efficient,transition-metal-and light-free approach to polyheterocycles via regioselective cascade radical cyclization is developed.The redox-neutral protocol has a broad substrate scope with good functional group tolerance and probably undergoes a SET process,which is initiated by catalytic amounts of quinone in combination with 2.0 equiv.of Cs_(2)CO_(3).

Alkyl Radical Initiated Cyclization/Cascade for Synthesizing Lactam-Substituted Alkyl Sulfones

An alkyl radical initiated cyclization/tandem reaction of alkyl bromides and alkyl electrophiles by using potassium metabisulphite(K_(2)S_(2)O_(5))as a connector is developed for the synthesis of various lactam-substituted alkyl sulfones.Notably,this process does not require a metal catalyst or metal powder reductant,highlighting its environmentally friendly features.The reaction demonstrates outstanding substrate adaptability and a high tolerance towards diverse functional groups.Furthermore,the biologically active molecules and commercially available drugs with a late-stage modification are also highly compatible with this transformation.Mechanistic studies revealed that the reaction proceeds through a single-step process involving intramolecular radical cyclization,"SO_(2)"insertion,and external alkyl incorporation.

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.

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.

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.

Metal-Free Arylsulfonyl Radical Triggered Cascade Cyclization of Phenyl-Linked 1,6-Enynes:Synthesis of 2,3-Dihydro-1H-indenes and 10a,11-Dihydro-10H-benzo[b]fluorines

Aryl sulfonyl radical triggered cascade cyclization of phenyl-linked 1,6-enynes for the synthesis of biologically important indenes containing alkenyl C—X bonds and 10a,11-dihydro-10H-benzo[b]fluorines is presented.In these radical cascade processes,three new chemical bonds,including C—S,C—C,and C—X bonds,and three C—C bonds are formed in one step.The method is attractive and valuable due to its metal-free,mild reaction conditions,broad substrate scope and good functional group tolerance.

Visible-light-promoted Radical Cyclization/Arylation Cascade for the Construction of α,α-Difluoro-γ-Lactam-Fused Quinoxalin-2(1H)-Ones

A visible-light-induced tandem radical intramolecular cyclization/arylatiion of quinoxalin-2(1H)-ones with bromodifluoroacetamides is described.This protocol allows efficient access to a variety of valuableα,α-difluoro-y-lactam-fused quinoxalin-2(1H)-ones in moder-ate to good yields under metal-free,mild and redox neutral reaction conditions.This strategy is tolerant of various functional groups and a broad range of substrates.The mechanism experiments suggested an involvement of 5-exo-trig cyclization and a radical pro-cess in this transformation.

Recent advances in visible-light photoredox-catalyzed nitrogen radical cyclization

Visible-light photoredox catalysis is a powerful and attractive strategy for organic molecule activation and new reaction design owing to its environmental-friendly characteristics and unique catalytic mechanisms,and has found wide applications in organic synthesis.This catalytic strategy enables controllable generation of diverse nitrogen-centered radicals(NCRs)under mild conditions,providing access to construction of diverse nitrogencontaining compounds.In this review,we critically illustrate the recent advances in the field of visible-light photoredox-catalyzed cyclization of nitrogen-centered radicals,based on the different radical precursors and activation modes.Wherever possible,particular emphasis is also put on working models and synthetic applications.