1,1 -Dipheny lethylene

The mechanism of the ligand coupling or reductive elimination step is not well understood and rather speculative. However, the possible intermediacy of radical species, either free or in-cage, has been considered unlikely, since the use of free-radical traps did not alter the outcome of the reactions. The use of an external trap (1,1-dipheny-lethylene)31,40 (Equation (13)) or the use of the classical internal intramolecular free-radical probe [(o-allyloxy)phenyl radical]41 or its diphenyl analog ]( -2,2-diphenylallyloxy)phenyl radical]42 (Equation (14)) did not interfere with the outcome of the arylation reaction, thus excluding the possibility of the intermediacy of free radicals. 

It was anticipated that the copolymerization of substituted 1,1-dipheny-lethylenes with dienes such as butadiene and isoprene would be complicated by the very unfavorable monomer reactivity ratio for the addition of poly(-dienyl)lithium compounds to 1,1-diphenylethylene [133, 134]. Yuki and Oka-moto [133, 134] calculated values of ri=54 and ri=29 in hydrocarbon solutions for the copolymerization of 1,1-diphenylethylene (M2) with butadiene (Mi) and isoprene (Mi), respectively. Although the corresponding values in THE are ri(butadiene)=0.13 and ri(isoprene)=0.12, this would not be an acceptable solution since THE is known to form polymers with high 1,2-microstructures [3]. Anionic copolymerizations of butadiene (Mi) with excess l-(4-dimethyla-mino-phenyl)-l-phenylethylene (M2) were conducted in benzene at room temperature for 24-48 h using scc-butyllithium as initiator [189]. Anisole, triethy-lamine and ferf-butyl methyl ether were added in ratios of [B]/[RLi]=60, 20, 30, respectively, to promote copolymerization and minimize 1,2-enchainment in the polybutadiene units. Narrow molecular weight distribution copolymers with Mn=14xl0 to 32x10 (Mw/Mn=1.02-1.03) and 8, 12, and 30 amine... 

These procedures have also been applied to the synthesis of 1,1-dipheny-lethylene-functionalized polybutadiene macromonomers (79) [208, 209]. The general reaction scheme is shown in Eq. (45) ... 

Scheme 4.17 Synthesis of 4-arm ABCD miktoarm star polymers using 4-(dichloromethylsilyl) dipheny lethylene.

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