Atom transfer radical addition catalyzed

The addition of halocarbons (RX) across alkene double bonds in a radical chain process, the Kharasch reaction (Scheme 9.29),261 has been known to organic chemistry since 1932. The overall process can be catalyzed by transition metal complexes (Mt"-X) it is then called Atom Transfer Radical Addition (ATRA) (Scheme 9.30).262... 

Transition metal-catalyzed atom transfer radical addition Atom transfer radical polymerization Equilibrium constant for atom transfer Activation rate constant for atom transfer Deactivation rate constant for atom transfer 2,2 -Bipyridine... 

Fiirstner reported the first McMurry-type reactions working with 5-10 mol% of titanium trichloride and stoichiometric amounts of zinc powder in the presence of chlorotrimethylsilane. The amount of TiCl3 could be reduced to 2 mol% when (ClMe2SiCH2)2 was used as a reagent [125, 131]. At the same time, Burton and coworkers reported atom transfer radical additions of perfluoroalkyl iodides 39 to alkenes 40 catalyzed by 20 mol% of a low-valent titanium compound generated from TiCLt and zinc powder affording 41 in 10-85% yield (Fig. 13). A tandem radical addition/5-exo cyclization/iodine transfer reaction with diallyl ether proceeded in 66% yield [132]. 

Fig. 13 Low-valent titanium-catalyzed atom transfer radical additions...

Fig. 37 Atom transfer radical addition reactions catalyzed by molybdenum complexes...

Nedelec and coworkers reported a manganese(III)-initiated cyanoacetate-catalyzed atom-transfer radical addition of polyhalomethanes or dibromomalonate 172 to alkenes 126 (Fig. 48) [272]. Since neither Mn(II) nor Mn(III) is useful to initiate Kharasch-type additions, an organocatalyst served this purpose. Thus, a short electrolysis of a mixture of 126,172,10 mol% of Mn(OAc)2, and 10 mol% of methyl cyanoacetate 171 led to initial oxidation of Mn(II) to Mn(III), which served to form the cyanoacetate radical 171A oxidatively. The latter is able to abstract a halogen atom from 172. The generated radical 172A adds to 126. The secondary... 

Cu(0)-Catalyzed Atom Transfer Radical Addition Reactions. 384... 

Fig. 36 Pd(0)-catalyzed atom transfer radical addition reactions...

This catalytic sequence is known as Kharasch addition or atom transfer radical addition (ATRA) [4]. Various polyhalogenated compounds such as CCI4 and CCI3CO2R are used as the organic halides, and transition metal salts or complexes are used as the catalyst [3]. Intramolecular version of the Kharasch addition reaction (atom transfer radical cyclization, ATRC) has opened novel synthetic protocols to the synthesis of carbocyde or heterocyles catalyzed by transition metals [5-7], and this has become a very important field in free radical cydization in organic synthesis. Transition metal-catalyzed Kharasch reactions sometimes afford telomers or poly-... 

Metal-catalyzed living radical polymerization can be traced back to metal-catalyzed radical addition reactions to alkenes, sometimes collectively called Kharasch or atom-transfer radical addition (ATRA) reactions in organic chemistry (Scheme 2).33 Thus, a... 

Scheme 27 The Tp Cu-catalyzed atom transfer radical addition reaction...

Greening of Copper Catalyzed Atom Transfer Radical Addition (ATRA) and Cyclization (ATRC) Reactions... 

A parallel development was initiated by the first publications from Sawamoto and Matyjaszweski. They reported independently on the transition-metal-catalyzed polymerization of various vinyl monomers (14,15). The technique, which was termed atom transfer radical polymerization (ATRP), uses an activated alkyl halide as initiator, and a transition-metal complex in its lower oxidation state as the catalyst. Similar to the nitroxide-mediated polymerization, ATRP is based on the reversible termination of growing radicals. ATRP was developed as an extension of atom transfer radical addition (ATRA), the so-called Kharasch reaction (16). ATRP turned out to be a versatile technique for the controlled polymerization of styrene derivatives, acrylates, methacrylates, etc. Because of the use of activated alkyl halides as initiators, the introduction of functional endgroups in the polymer chain turned out to be easy (17-22). Although many different transition metals have been used in ATRP, by far the most frequently used metal is copper. Nitrogen-based ligands, eg substituted bipyridines (14), alkyl pyridinimine (Schiff s base) (23), and multidentate tertiary alkyl amines (24), are used to solubilize the metal salt and to adjust its redox potential in order to match the requirements for an ATRP catalyst. In conjunction with copper, the most powerful ligand at present is probably tris[2-(dimethylamino)ethyl)]amine (Mee-TREN) (25). 

ATRP is an extension of atom transfer radical addition (ATRA), which is a well-known method of carbon-carbon bond formation (catalyzed by transition metal complexes) in organic synthesis. ATRP also has roots in the transition metal catalyzed telomerization reactions (Boutevin,... 

Thus, complex 15a catalyzed the atom transfer radical addition (ATRA) of CCI4 and CHCI3 to olefins at 0°C to 40°C with very high turnover numbers (TONs) and frequencies. Replacement of the p-cymene ligand with 1,3,5-triisopropylbenzene enhaneed the solubility of eomplex 15b in hydrocarbon solvents and allowed to use it for promoting atom transfer radical polypolymerization (ATRP) of vinyl monomers in toluene. ... 

Eckenhoff WT, Pintauer T. Copper catalyzed atom transfer radical addition (ATRA) and cyclization (ATRC) reactions in the presence of reducing agents. Catal. Rev. 2010 52 (l) l-59. 

Thommes K, Ifli B, Scopelliti R, Severin K. Atom-transfer radical addition (ATRA) and cylization (ATRC) reactions catalyzed by a mixture of [RuCl2Cp (PPh3)] and magnesium. Chem. Eur. J. 2007 13(24) 6899-6907. 

Nair RP, Kim TH, Frost BJ (2009) Atom transfer radical addition reactions of CCI4, CHCI3, and p-tosyl chloride catalyzed by Cp Ru(PPh3)(PR3)Cl complexes. Organometallics 28 4681 688... 

Peeters et al. combined the enantioselective eROP of 4-methyl-e-caprolactone (4-MeCL) with controlled atom transfer radical polymerization (ATRP) of methyl methacrylate (Scheme 11.17) [58]. It was found that the addition of Ni(PPh3)4 inhibited Novozym 435 and at the same time catalyzed the ATRP reaction. On the other hand, Novozym 435 did not interfere with the ATRP of methyl methacrylate. As a result the sequence of the reaction was important first the enantioselective eROP of 4-MeCL was conducted at low temperature to have a high enantioselectivity until the conversion was around 50%. Then, Ni(PPh3)4 and MM A were added and the temperature was raised to 80 °C to start up the ATRP reaction of MM A. After precipitation of the polymer to remove the unreacted (R)-4-MeCL, the chiral block copolymer (Mn= llkgmoT1 and 17 kg mol 1) was... 

CRP LRP in Figure 1), ATRP or atom transfer (radical) polymn ( ATRP only , this search does not include terms such as metal mediated or metal catalyzed (living) radical polymerization), NMP or SFRP or nitroxide mediated polymn ot stable free polymn ( SFRP NMP ) and RAFT ox reversible addition transfer or degenerative transfer or catalytic chain transfer ( RAFT DT CT ). The latter two terms were refined with a term radical polymn since they coincide with other common chemical names such as N-methylpyrrolidone or raft-associated proteins. In summary, since 1995 over... 

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