Fluorinated Bis(phenoxyketimine)titanium Complexes for the Living, Isoselective Polymerization of Propylene: Multiblock Isotactic Polypropylene Copolymers via Sequential Monomer Addition
摘要:
A series of bis(phenoxyketimine)titanium dichloride complexes were synthesized and evaluated as catalysts for living, isoselective propylene polymerization upon activation with methylaluminoxane (MAO). Catalysts bearing phenoxyketimine ligands with different substituents at the ortho and para. positions of the phenolate ring and substituents at the ketimine carbon were investigated. The identity of the ketimine substituent had the largest effect on the activity and isoselectivity of propylene polymerization. Complex 12/MAO promoted the living, isoselective polymerization of propylene ([m(4)] = 0.73, alpha = 0.94). This catalyst system was used for the synthesis of a number of block copolymers featuring isotactic polypropylene semicrystalline blocks and poly(ethylene-co-propylene) amorphous blocks. Several triblock samples with varying block lengths, a pentablock, and a heptablock copolymer were synthesized. Mechanical testing has revealed that each is elastomeric with elongations at break between similar to 790-1000%.
Pd(II)-Catalyzed Olefination of <i>sp</i><sup>3</sup> C−H Bonds
作者:Masayuki Wasa、Keary M. Engle、Jin-Quan Yu
DOI:10.1021/ja1010866
日期:2010.3.24
using N-arylamide directing groups. Following olefination, the resulting intermediates were found to undergo rapid 1,4-addition to give the corresponding gamma-lactams. Notably, this method was effective with substrates containing alpha-hydrogen atoms and could be applied to effect methylene C-H olefination of cyclopropane substrates.
Amide-directed arylation of sp3 C–H bonds using Pd(II) and Pd(0) catalysts
作者:Masayuki Wasa、Jin-Quan Yu
DOI:10.1016/j.tet.2010.03.111
日期:2010.6
Protocols to effect β-arylation of sp3 C–Hbonds via Pd(II)/(IV) and Pd(0)/(II) catalytic cycles have been achieved using a newly developed monodentate CONHC6F5 directing group. These reactions provide an unprecedented means to functionalize sp3 C–Hbonds in aliphatic carboxylic acid-derived substrates.
Base-catalyzed synthesis of aryl amides from aryl azides and aldehydes
作者:Sheng Xie、Yang Zhang、Olof Ramström、Mingdi Yan
DOI:10.1039/c5sc03510d
日期:——
Aryl amides are efficiently synthesized from the rearrangement of triazolines, which formed in the base-catalyzed azide–aldehyde cycloaddtion.
芳基酰胺可以通过三唑烯的重排合成,三唑烯是在碱催化的叠氮化物-醛环加成中形成的。
Pd(0)/PR<sub>3</sub>-Catalyzed Intermolecular Arylation of sp<sup>3</sup> C−H Bonds
作者:Masayuki Wasa、Keary M. Engle、Jin-Quan Yu
DOI:10.1021/ja903573p
日期:2009.7.29
Pd(0)-catalyzedintermolecular arylation of sp(3) C-H bonds has been achieved using PR(3)/ArI. This protocol can be used to arylate a variety of aliphatic carboxylic acid derivatives, including a number of bioactive drug molecules. The use of fluorinated aryl iodides also allows for the introduction of fluorine into a molecule of interest.
Synthesis and Characterization of Group 4 Fluorinated Bis(amidinates) and Their Reactivity in the Formation of Elastomeric Polypropylene
作者:Tatyana Elkin、Sinai Aharonovich、Mark Botoshansky、Moris S. Eisen
DOI:10.1021/om300702s
日期:2012.11.12
Bis(amidinate) titanium and zirconium bis-(dimethylamido) complexes were prepared, and the dynamic behavior of the titanium complex containing perfluorinated amidinate ligand (11) was studied in detail. The variable temperature NMR revealed the presence of two species in solution, in line with the different connection modes of the ligand to the metal center. The resulting complexes were tested as catalysts in the polymerization of propylene, and the resulting polymers were consistent with elastomeric high-molecular-weight atactic polypropylenes.