Atom transfer radical coupling

This reaction is based on the Wurtz [158,159] radical coupling. Two teams developed at the same time this radical coupling, also called atom transfer radical coupling (ATRC) [ 160-164]. 

THE USE OF ATOM TRANSFER RADICAL COUPLING REACTIONS FOR THE SYNTHESIS OF VARIOUS MACROMOLECULAR STRUCTURES... 

The use and limitations of Atom Transfer Radical Coupling (ATRC) reactions including polyrecombination reactions for the preparation of telechelic polymers, segmented block copolymers, and polycondensates are presented. Specifically, the preparation of telechelic polymers with hydroxyl, aldehyde, amino and carboxylic functionalities, poly(/i-xylylene) and its block copolymers, and polyesters via ATRC process is described. The method pertains to the generation of biradicals at high concentration from polymers prepared by ATRP or specially designed brfunctional ATRP initiators. The possibility of using silane radical atom abstraction (SRAA) reactions, that can be performed photochemically in the absence of metal catalysts, as an alternative process to ATRC is also discussed. 

Diblock copolymer of polystyrene and aromatic polyether was also synthesized by CGCP of ether monomer 20 with orthogonal initiator, which was composed by both the initiation site of CGCP and that of ATRP, followed by ATRP of styrene [60]. During study of ATRP of styrene fi-om polyamide macroinitiator, we discovered styrene-assisted atom transfer radical coupling (ATRC) from methacrylic... 

Recently, Tillman and coworkers [65] reported an intramolecular radical trap-assisted atom transfer radical coupling (IRT-ATRC) as shown in Scheme 15. The a,a)-dibromo functional PSTY was first synthesized by ATRP. The bromo chain end was first activated by CuBr/MegTREN complex to yield a radical that simultaneously reacted with 2-methyl-2-nitrosopropane to form a nitroxide radical. The another bromo chain end was also activated to a radical and rapidly trapped by nitroxide radical through the well-known ATRC process to form cyclic PSTY. However, in this case, the hydrodynamic volume changes ( = Mpc/Mpi) from linear to cyclic were mostly greater than 0.85, which is much higher than that of cyclic PSTY made from anionic polymerization (i.e., 0.78). Although the authors ascribed the reason to... 

Scheme 15 Synthesis of cyclic PSTY through radical trap-assisted atom transfer radical coupling (RTA-ATRC)...

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... 

Tsarevsky, N. V. Matyjaszewski, K. Reversible redox cleavage/coupling of polystyrene with disulfide or thiol groups prepared by atom transfer radical polymerizaion. Macromolecules 2002, 35, 9009. 

It was reported that Pd(0)-catalyzed coupling reactions of allenic alcohols, amines and acids with hypervalent iodonium salts afforded cyclized heterocyclic tetrahydrofurans, tetrahydropyrans, pyrrolidines, piperidines, or lactones under mild conditions <99SL324>. Intramolecular 1,5-hydrogen atom transfer radical cyclization reaction of pyrrolidine derivatives was examined. Reaction of 3,4-dialiyloxy-JV-(0-bromobenzyl)pyrtolidine gave hexahydro-... 

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-... 

The most prominent reactions catalyzed by low-valent iron species involving radical intermediates are cross-coupling reactions of alkyl halides (recent reviews [32-35]) and atom transfer radical reactions. In cross-coupling reactions the oxidation state of the catalytically active species can vary significantly depending on the reaction conditions very often it is not known exactly. To facilitate a summary, all iron-catalyzed cross-coupling reactions are treated together and involved oxidation states, where known, are mentioned at the example. In contrast, iron-catalyzed Kharasch reactions will be treated at the oxidation state of the iron precursors. 

Tsarevsky, N.V. Sumerlin, B.S. Matyjaszewski, K. Step-growth click coupling of telechelic polymers prepared by atom transfer radical polymerization. Macromolecules 2005, 38 (9), 3558-3561. 

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