Carbon atom transfer radical

ORl OX w di-Miutyl peroxyoxalalc deactivation by reversible chain transfer and bioinolecular aclivaiion 456 atom transfer radical polymerization 7, 250, 456,457, 458,461.486-98 deactivation by reversible coupling and untmolecular activation 455-6, 457-86 carbon-centered radical-mediated poly nierizaiion 467-70 initiators, inferlers and iriiters 457-8 metal complex-mediated radical polymerization 484... 

Carbon-carbon bond formation is a fundamental reaction in organic synthesis [1, 2,3,4], One way to form such a bond and, thus, extend a carbon chain is by the addition of a polyhalogenated alkane to an alkene to form a 1 1 adduct, as shown in Scheme 1. This reaction was first reported in the 1940s and today is known as the Kharasch addition or atom transfer radical addition (ATRA) [5,6], Historically, Kharasch addition reactions were conducted in the presence of radical initiators or... 

Kong H, Gao C, Yan DY (2004). Functionalization of multiwalled carbon nanotubes by atom transfer radical polymerization and defunctionalization of the products. Macromolecules 37 ... 

B. Fragneaud, K. Masenelli-Varlot, A. Gonzalez-Montiel, M. Terrones, J.Y. Cavaille, Efficient coating of N-doped carbon nanotubes with polystyrene using atomic transfer radical polymerization., Chemical Physics Letters, vol. 419, pp. 567-573, 2006. 

Qin, S., et al., Polymer brushes on single-walled carbon nanotubes by atom transfer radical polymerization ofn-butyl methacrylate. Journal of the American Chemical Society, 2003. 126(1) p. 170-176. 

Another application of ruthenium indenylidene complexes was the atom transfer radical addition of carbon tetrachloride to vinyl monomers reported by Verpoort [61]. This Kharasch reaction afforded good yields for all substrates tested, especially with the catalyst VIII (Equation 8.11, Table 8.8). 

The synthesis of mixed peroxides formed from /-butyl hydroperoxide and carbon-centred radicals has been studied. The reactions were strongly effected by solvents as well as catalytic amounts of Cun/Fem. The kinetic data suggest that the conditions for the Ingold-Fischer persistent radical effect are fulfilled in these cases.191 The use of Cu /Cu" redox couples in mediating living radical polymerization continues to be of interest. The kinetics of atom-transfer radical polymerization (ATRP) of styrene with CuBr and bipyridine have been investigated. The polymer reactions were found to be first order with respect to monomer, initiator and CuBr concentration, with the optimum CuBr Bipy ratio found to be 2 1.192 In related work using CuBr-A-pentyl-2-... 

Xia, J. H. Johnson, T. Gaynor, S. G. Matyjaszewski, K. DeSimone, J. Atom Transfer Radical Polymerization in Supercritical Carbon Dioxide. Macromolecules 1999, 32, 4802-4805. 

A second type of reaction that involves the formal addition of a carbon-halogen bond to a double carbon-carbon, both inter- and intramolecularly, will also be discussed. These are the atom transfer radical reactions, and also include the polymerization of some olefins such as styrene or acrylates. 

To promote a polymerization, the newly formed carbon-halogen bond must be capable of being reactivated and the new radical must be able to add another alkene. This was accomplished for the radical polymerizations of St and methyl acrylate (MA), which were initiated by 1-phenylethyl bromide and catalyzed by a Cu(I)/2,2 -bipyridine (bpy) complex [42,79-81]. The process was called Atom Transfer Radical Polymerization (ATRP) to reflect its origins in ATRA. A successful ATRP relies on fast initiation, where all the initiator is consumed quickly, and fast deactivation of the active species by the higher oxidation state metal. The resulting polymers are well defined and have predictable molecular weights and low polydispersities. Other reports used different initiator or catalyst systems, but obtained similar results [43,82]. Numerous examples of using ATRP to prepare well-defined polymers can now be found [44-47,49]. Scheme 4 illustrates the concepts of ATRA and ATRP. To simplify schemes 3,4 and 5, termination was omitted. 

Figure 3.86 Attaching an initiator molecule like bromoisobutyric acid has proven a suitable strategy for the atom-transfer radical polymerization (ATRP) starting from carbon nanotubes.

The paper generally recognized as the first report of an atom transfer radical addition reaction involving carbon-carbon bond formation and yielding a monomeric product was that of Kharasch et al., in which CCI4 was shown to add to... 

Atom transfer radical methodology was also explored in the 1-endo cyclizations. Curran and Chang [71] have investigated the cyclization of a-iodoesters. Photolysis of the a-iodo ester and a-iodo malonates 280 in the presence of hexabutyldistannane generated a mixture of the 6-exo and 1-endo trig radical cyclized iodides 281 and 282. Quite expectedly, the presence of a methyl group on the internal carbon of the olefin (283) shifted the reaction to 1-endo mode exclusively. The product underwent spontaneous cyclization to furnish the lactone 284. 

Heise, Palmans, de Geus, Villarroya and their collaborators (17,41,42) have been working on a chemoenzymatic cascade synthesis to prepare block copolymers. They combine enzymatic ring-opening polymerization (eROP) and atom transfer radical polymerization (ATRP). The synthesis of block copolymers was successful in two consecutive steps, i.e., eROP followed by ATRP. In the one-pot approach, block copolymers could be obtained by sequential addition of the ATRP catalyst, but side reactions were observed when all components were present from at the onset of reactions. A successful one-pot synthesis was achieved by conducting the reaction in supercritical carbon dioxide. 

Slightly modified systems were subsequently used in a conhnuous-flow membrane reactor for the atom-transfer radical addihon of carbon tetrachloride to methyl methacrylate (9) [18],... 

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