Highly Efficient Copper‐Mediated Atom‐Transfer Radical Addition (ATRA) in the Presence of Reducing Agent

Highly Efficient Ambient‐Temperature Copper‐Catalyzed Atom‐Transfer Radical Addition (ATRA) in the Presence of Free‐Radical Initiator (V‐70) as a Reducing Agent

“…[13,14] ). [24] ATRA of these monomers in the presence of AIBN at 60 8C yielded significant amounts of polymers/telomers unless high copper loadings and/or large excess of alkyl halide (4 equiv relative to alkene) were used.…”

“…[12] Even more impressive TONs were achieved with CBr 4 and [Cu II A C H T U N G T R E N N U N G (tpma)Br][Br] (tpma = tris(2-pyridylmethyl)-A C H T U N G T R E N N U N G amine) complex (as high as 160 000), enabling efficient ATRA reactions in the presence of as little as 5 ppm of copper. [13] Since the seminal reports by our research group [14] as well as Severins, [12] this method of catalyst regeneration in ATRA has attracted considerable academic interest, [15][16][17][18][19][20][21][22] and was even successfully applied to intramolecular ATRA or atom-transfer radical cyclization (ATRC) reactions.…”

“…Originally, the solution to this problem has been found for copper-catalyzed atom-transfer radical polymerization (ATRP), [3,10,11] and was subsequently applied first to ruthenium- [12] and then copper-catalyzed [13,14] ATRA reactions. In all of these processes, the activator (transition-metal complex in the lower oxidation state) is continuously regenerated from deactivator (transition-metal complex in the higher oxidation state) in the presence of reducing agents, such as phenols, glucose, ascorbic acid, hydrazine, tin(II) 2-ethylhexanoate magnesium, and free-radical initiators (Scheme 1).…”

Copper‐Catalyzed Synthesis of 1,2‐Disubstituted Cyclopentanes from 1,6‐Dienes by Ring‐Closing Kharasch Addition of Carbon Tetrachloride

“…[30,31] This strategy is based in the use of a constant source of organic free radicals to regenerate the Cu(I) activator, which is otherwise consumed in termination reactions. After this report, Severin [32] and Pintauer [33] have employed the same technique in ATRA reactions catalyzed by ruthenium and copper complexes, respectively. One of the possible reducing agents is AIBN, but the use of this compound has some problems.…”

Structural and Mechanistic Aspects of Copper Catalyzed Atom Transfer Radical Polymerization

“…However, the role of counterion coordination (in particular Br − and Cl − ) in these complexes still remains very unclear. Recently, we were able to isolate and structurally characterize neutral Cu I (TPMA)Cl [118] and Cu I (TPMA)Br [119] complexes. To our surprise, both complexes were pseudopentacoordinated ( Fig.…”