Cycloolefins stereochemistry

The cis-stereochemistry of the hydroalumination of olefins is proved by the reaction of a strained cycloolefin, 1,1-dimethylindene, with i-Bu2AlD in the presence of Et20 (to slow down the inversion process of the Al—C bond). The deuterolysis of the Al—C bond (retention of configuration) leads to pure cis-2,3-dideuterio-l,l-dimethylindane ... 

SCHEME 16.2 Stereochemistry during the polymerization of a prochiral cycloolefin such as norbornene nsing Cs- (A) and C2-symmetiic (B) catalysts. Independent of the relative topicities of the single insertion events (contrasted by pathways a and b), apphcation of the mechanisms known from a-olefin polymerization predict an erythrodisyndiotactic polymer to be formed by C -symmetric catalysts and an erythrodiisotactic polymer to be formed by C2-symmetric catalysts. 

Copolymers of several cycloolefins with norbornene and/or norbornadiene have been widely explored with catalytic systems based on tungsten and molybdenum compounds. Products of varying compositions, of interest for their plastic or elastomeric properties, have been prepared by this way. Valuable information concerning reaction mechanisms and stereochemistry... 

The stereochemistry of the reaction has been of interest for a long time already in order to predetermine the structure of the products. In recent years, however,the stereochemistry has been investigated in order to gain additional support for one or the other mechanism. Most investigations have been performed with acyclic olefins. But there are some involving cycloolefines as well. 

Abstract Metallocene complexes that serve as stereoselective olefin polymerization catalysts are described. The polymerization of propylene, styrene, methyl methacrylate, 1,3-dienes, non-conjugated dienes and cycloolefins is discussed. The stereochemistry of monomer insertion is governed by the chiral steric environment of catalysts derived from a ligand structure (catalytic-site control) or a chiral center in the polymer chain (chain-end control). The mechanism of formation of isotactic and syndiotactic polymers in each monomer and catalyst is explained. Non-metallocene catalysts for stereospecific polymerization are also mentioned. 

There is a large amount of literature and many patents in this area, as well as many good reviews and books [8,9,10,11,12,13,14,15,16,17,18,19]. The recent review by Coates [10] describing stereoselective polymerization overlaps considerably with this chapter, and is recommended for consultation. In this chapter, metallocene-catalyzed olefin polymerization is discussed, focusing on the synthesis of stereoregulated polymers. The aim of this review is not to be a complete survey the outline and some recent topics in polymerization of propylene, higher a-olefins, styrene, acrylate esters such as methyl methacrylate (MMA), 1,3-butadienes, and cycloolefins will be described. Polyethylene is one of the most important commercially manufactured polymers. The homopolymer, as well as the copolymer with ethylene and other olefins, is an important subject in the polyolefin industry. However, it will be only briefly mentioned because the stereochemistry is less involved. 

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