Imines metalated

Terminally brominated PE as PE macroinitiator can be produced by other methods. It has been reported that vinyl terminated PE produced by a bis(phenoxy-imine)metal complex and MAO catalyst system (Mn = 1800, Mw/Mn = 1.70) was converted to terminally 2-bromoisobutyrate PE through the addition reaction of 2-bromoisobutyric acid to the vinyl chain end. Polyethylene-Wodc-poly( -bulyl acrylate) (PE-fo-PnBA) from terminally brominated PE by ATRP procedure has also been produced [68]. It was reported that degenerative transfer coordination polymerization with an iron complex can be used to prepare terminally brominated PE as a macroinitiator [69]. A Zn-terminated PE prepared using an iron complex and diethylzinc,... 

Polyethylene-Wock-poly(clhylcnc-co-norbornene) (PE-fo-P(E-co-NBl ) block copolymer was successfully synthesized by a titanium complex with two non-symmetric bidentate /J-cnaminokclonalo ligands [136,137]. Bis(pyrrolide-imine)titanium complex also has the ability to produce the PE-fo-P(E-co-NBE) block copolymer. PE-fo-PS was synthesized via sequential monomer addition during homogeneous polymerization with bis(phenoxy-imine)metal catalysts [138]. 

In general, ketones are predicted to metalate via the open dimer pathway whereas imine metallations proceed more readily via monomers. By contrast, increased steric demands of the substrates promote the monomer pathways. It is reasonable to ascribe this to a decrease in congestion in monomers relative to open dimers. Indeed, for metalla-tion of imine 2 with LDA in THF (4 must be a real species) the rate behavior was consistent with the mechanism specified by M-1. When 2 2 TMEDA-LDA complex 1 was used for deprotonation of 3, a solvent-free open dimer proved to be a plausible reactive intermediate (Sch. 5) [28]. Accordingly, the rate of imine metalation depends strongly on the solvent and substrate used [29]. Kinetic evidence obtained in the enolization experiment with sterically demanding ester 5 showed disolvated LDA monomers to be the reactive form, providing the first direct support for Ireland s hypothesis of cyclic transition state... 

Activation of amines with low-valent palladinm catalysts gives two types of intermediates. One is the reaction of primary and secondary amines bearing N—bonds with palladinm to give imine metal complexes 1 (Scheme The other is the reaction of... 

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