Atom Transfer Radical Addition Research Articles

Crystal structure of {(but-3-en-1-yl)bis-[(pyridin-2-yl)meth-yl]amine-κ(3) N,N',N''}di-chlorido-copper(II) diethyl ether hemisolvate.

The five-coordinate Cu(II) atom in the title complex [CuCl2(C16H19N3)]·0.5C4H10O, adopts a near-ideal square-pyramidal geometry (τ-5 = 0.01). The apical Cu-Cl distance is 0.2626 (6) Å longer than the basal Cu-Cl distance. Weak C-H⋯Cl interactions between pyridine rings and the Cl atoms of adjacent complex molecules are present. The solvent molecule, located on a twofold rotation axis, is situated in the voids of this arrangement. Copper atoms coordinated by tridentate nitro-gen-containing ligands have been found to be excellent promoters of Atom Transfer Radical Addition (ATRA) reactions.

Atom transfer radical addition (ATRA) catalyzed by copper complexes with N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) ligand

Synthesis, characterization, electrochemical studies and ATRA activity of copper complexes with N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) ligand in the presence of ascorbic acid as a reducing agent were reported. [CuII(TPEN′)Br][Br] (TPEN′ denotes tetracoordinated ligand) catalyst showed a very low activity in ATRA of CBr4 to 1-octene, methyl methacrylate, methyl acrylate and styrene in methanol, which is a typical solvent used for ATRA reactions employing ascorbic acid. On the contrary, the yields and stereoselectivity towards monoadduct formation were dramatically increased in slightly polar but aprotic acetone. Based on molecular structures of isolated [CuII(TPEN)][BPh4] and [CuII(TPEN′)Br][Br] complexes, as well as UV–Vis and cyclic voltammetry studies, an equilibrium was proposed involving inactive [CuII(TPEN)]2+ and ATRP active [CuII(TPEN′)Br]+ cations The halidophilicity of the bromide-based deactivating complex ([CuII(TPEN′)Br][Br]) decreased approximately 750 times upon changing the solvent from acetone (KBr = 3000 ± 230) to methanol (KBr = 4.1 ± 0.1), explaining poor catalytic activity in methanol. In acetone, [CuII(TPEN′)Br][Br] complex was nearly as active in ATRA reactions employing ascorbic acid as previously reported [CuII(TPMA)Br][Br].

Efficient Cu-catalyzed atom transfer radical addition reactions of fluoroalkylsulfonyl chlorides with electron-deficient alkenes induced by visible light.

Fluoroalkylsulfonyl chlorides, R(f)SO2Cl, in which R(f)=CF3, C4F9, CF2H, CH2F, and CH2CF3, are used as a source of fluorinated radicals to add fluoroalkyl groups to electron-deficient, unsaturated carbonyl compounds. Photochemical conditions, using Cu mediation, are used to produce the respective α-chloro-β-fluoroalkylcarbonyl products in excellent yields through an atom transfer radical addition (ATRA) process. Facile nucleophilic replacement of the α-chloro substituent is shown to lead to further diverse functionalization of the products.

Efficient Cu‐catalyzed Atom Transfer Radical Addition Reactions of Fluoroalkylsulfonyl Chlorides with Electron‐deficient Alkenes Induced by Visible Light

AbstractFluoroalkylsulfonyl chlorides, RfSO2Cl, in which Rf=CF3, C4F9, CF2H, CH2F, and CH2CF3, are used as a source of fluorinated radicals to add fluoroalkyl groups to electron‐deficient, unsaturated carbonyl compounds. Photochemical conditions, using Cu mediation, are used to produce the respective α‐chloro‐β‐fluoroalkylcarbonyl products in excellent yields through an atom transfer radical addition (ATRA) process. Facile nucleophilic replacement of the α‐chloro substituent is shown to lead to further diverse functionalization of the products.

Aromatic Aldehydes as Energy-Transfer Photoorganocatalysts

New photochemical life of ArCHO: The recent breakthrough discovery by Melchiorre and co-workers in the use of aromatic aldehydes as energy-transfer photoorganocatalysts in atom-transfer radical addition reactions is discussed. ISC=Intersystem crossing; X=I, Br, Cl.

Atom Transfer Radical Addition/Polymerization of Perfluorosulfonic Acid Polymer with the C-F Bonds as Reactive Sites.

This work reports the first demonstration of the chemical reactions on the C-F groups of perfluorosulfonic acid polymers. The Nafion chains show chemical reactivity for atom transfer radical addition onto multiwalled carbon nanotubes and ability to serve as a macroinitiator for atom transfer radical polymerization. The C-F groups and mainchain -CF2 groups have been demonstrated, under a study with 19F NMR, as the active sites responsible for the reactions. The results could certainly extend both the scopes of chemistry and application of perfluorosulfonic acid polymers as well as the windows of atom transfer radical addition/polymerization to fluorinated compounds.

Intermolecular atom transfer radical addition of α,α,α-trichloromethyl ketones and alkenes mediated by a CuCl/bpy system

An atom transfer radical addition reaction between a,a,a-trichloromethyl ketones and alkenes mediated by a CuCl/bpy system is reported, which presents a good example of intermolecular atom transfer radical addition reactions.

Regioisomerized atom transfer radical addition (ATRA) of olefins with dichlorofluorocarbons

The Cu(i) catalysed atom transfer radical addition of dichlorofluorocarbons to olefins via C–Cl bond homolysis is successfully carried out.

Chloro, difluoromethylation and chloro, carbomethoxydifluoromethylation: reaction of radicals derived from RfSO2Cl with unactivated alkenes under metal-free conditions.

Difluoromethyl and carbomethoxydifluoromethyl radicals were generated from their respective sulfonyl chlorides under mild, metal-free conditions leading to efficient atom transfer radical additions (ATRA) to unactivated alkenes to form chloro, difluoromethylated and chloro, carbomethoxydifluoromethylated products.

ChemInform Abstract: Copper in Photocatalysis

AbstractReview: [33 refs.

ChemInform Abstract: Effect of Sodium Acetate in Atom Transfer Radical Addition of Polyhaloalkanes to Olefins.

AbstractPolyhaloalkanes undergo radical 1,2‐addition to olefins under thermal reaction conditions in the presence of NaOAc as an additive.

Photo‐Organocatalysis of Atom‐Transfer Radical Additions to Alkenes

AbstractWe have found that an organic molecule as simple as p‐anisaldehyde efficiently catalyzes the intermolecular atom‐transfer radical addition (ATRA) of a variety of haloalkanes onto olefins, one of the fundamental carbon–carbon bond‐forming transformations in organic chemistry. The reaction requires exceptionally mild reaction conditions to proceed, as it occurs at ambient temperature and under illumination by a readily available fluorescent light bulb. Initial investigations support a mechanism whereby the aldehydic catalyst photochemically generates the reactive radical species by sensitization of the organic halides by an energy‐transfer pathway.

Photo-organocatalysis of atom-transfer radical additions to alkenes.

We have found that an organic molecule as simple as p-anisaldehyde efficiently catalyzes the intermolecular atom-transfer radical addition (ATRA) of a variety of haloalkanes onto olefins, one of the fundamental carbon-carbon bond-forming transformations in organic chemistry. The reaction requires exceptionally mild reaction conditions to proceed, as it occurs at ambient temperature and under illumination by a readily available fluorescent light bulb. Initial investigations support a mechanism whereby the aldehydic catalyst photochemically generates the reactive radical species by sensitization of the organic halides by an energy-transfer pathway.

Copper in Photocatalysis

AbstractLight‐induced electron transfer (CuI to CuII), oxidative addition (CuI to CuIII), or the activation of copper alkene or alkyne complexes are possible key steps that offer unique possibilities for organic synthesis, including [2+2]‐cycloadditions, cross‐coupling reactions or atom transfer radical additions. This Minireview provides an overview on the photophysical properties of photocatalysts based on copper and on synthetic transformations mediated by them.

Building up polymer architectures on graphene oxide sheet surfaces through sequential atom transfer radical polymerization

ABSTRACTThe reactivity between the active species of atom transfer radical addition and the unsaturated groups of graphene oxides (GOs) has been demonstrated in this work. The reaction and the sequential surface‐initiated atom transfer radical polymerization provide a convenient approach to anchor various polymer chains and to buildup various polymer architectures, such as linear polymer, V‐shape block polymer, multibonded polymer layer, and hierarchical brush‐on‐layer polymer, on GO sheet surfaces. The chemical structures and morphology of the polymer‐modified GOs have been characterized with Fourier transform infrared spectroscopy, Raman spectroscopy, X‐ray photoelectron spectroscopy, and atomic force microscopy. After organomodification, the GOs exhibit a good dispersion ability in organic solvent over 80 days, amphiphilic characteristics, and temperature‐responsive properties. Reduction of the GOs has been performed to result in graphene‐like materials showing certain extent of electron conductivities. An effective approach to synthesize GO/polymer hybrid materials possessing various polymer architectures and attractive properties has been developed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1588–1596

Preparation of Chondroitin Sulfate-g-poly(ε-caprolactone) Copolymers as a CD44-Targeted Vehicle for Enhanced Intracellular Uptake

Chondroitin sulfate-g-poly(ε-caprolactone) (CP) copolymers were synthesized via atom transfer radical addition (ATRA). The CP copolymers self-assembled into micelles in water, and the micelles could be used to encapsulate a hydrophobic anticancer drug, camptothecin (CPT), in the core for tumor targeting delivery. The physicochemical properties of the micelles and CPT-loaded micelles were thoroughly characterized. For the in vitro test, the CPT release, the protection of the lactone ring of CPT from hydrolysis and the cellular uptake of CPT were studied. The cell-killing and apoptosis-inducing effects using the CPT-loaded micelles were significantly better than using free CPT against CRL-5802 cells. The micellar internalization into CRL-5802 cells was primarily via CD44 and clathrin dual-mediated endocytosis. For the in vivo test, the therapeutic efficacy of the CPT-loaded micelles was studied in a non-small-cell lung cancer xenograft animal model. The CPT-loaded micelles showed good inhibition in tumor growth as compared with a commercial product, CPT-11, in CRL-5802 tumor-bearing mice. The in vitro and in vivo data suggested the CP-based micelles are promising anticancer drug vehicles for lung cancer targeting.

Poly(3-hexyl thiophene)-b-Fullerene Functionalized Polystyrene Copolymers (P3HT-b-PSFu) as Compatibilizer in P3HT/Phenyl-C61-butyric Acid Methyl Ester (PCBM) Solar Cells

Poly(3-hexyl thiophene)-fullerene functionalized polystyrene block copolymers (P3HT-b-PSFu) with a variety of block lengths and compositions were synthesized by reacting P3HT macroinitiator with styrene and chloromethyl styrene via an atom transfer radical polymerization. After that, the prepared copolymers were reacted with C60 via an atom transfer radical addition to obtain P3HT-b-PSFu. Chemical structures and molecular weights of the products were characterized by1H-NMR, FTIR, and GPC, respectively. Next, the various P3HT-b-PSFu copolymers were added to P3HT/PCBM bulk heterojunction (BHJ) polymer solar cell. It was found that efficiency increased from 0.52% to the maximum value of 1.23%, after adding the copolymers.

Thermal and microwave assisted polymerization of vinyl acetate catalyzed by cyclometalated ruthenium (II) complexes

Polymerization of vinyl acetate (VAc) was carried out with four different cyclometalated ruthenium(II) catalysts, using CCl4 as initiator under conventional heating and microwave irradiation. The thermo-polymerizations were solvent-dependent and proceeded to limited conversions without control. Only the polymerization in DMSO mediated by [Ru(η6-C6H6)(C6H4-2-CH2NMe2)(MeCN)]PF6 (1) showed dependence of the molecular weights on conversion. Besides, this complex was the only one active under microwave irradiation. The microwave assisted polymerization was much faster than that under conventional heating, maintaining an increase of the molecular weights with conversion. The chain extensions were quite successful under both conventional heating and microwave irradiation, confirming the participation of ATRP mechanism. The complex 1 was active in atom transfer radical addition of CCl3Br to VAc substrate providing the adduct in high yield. Mechanistic studies demonstrated the importance of the presence of a labile benzene ligand to increase the catalytic activity of the ruthenium complexes.

Synthesis of Graft Copolymers and Their Preliminary Use as a Compatibilizer in Polymer Solar Cells

Poly(p-xylylene)-graft-poly(butylacrylate-g-fullerene) or PPX-g-PBAFu was synthesized by using Wessling route and atom transfer radical addition (ATRA) techniques. The graft copolymers were used as a compatibilizer in the bulk heterojunction (BHJ) polymer solar cells of poly(3-hexylthiophene) (P3HT) and fullerene (C60). The results from AFM micrographs showed that the phase size of P3HT and the aggregated C60 in the blended system was decreased from 300 to 30 nm after adding the copolymer (20 pph). Furthermore, the efficiencies of the BHJ cells from J-V curve were remarkably increased five times after adding the copolymer.

Photoredox catalyst-mediated atom transfer radical addition for polymer functionalization under visible light

A facile method for post-functionalization of polymers with side olefin groups was developed by visible light-mediated atom transfer radical addition (ATRA) employing a photoredox catalyst, fac-Ir(ppy)3.