Olefins polar-functionalized

The less hindered f/ans-olefins may be obtained by reduction with lithium or sodium metal in liquid ammonia or amine solvents (Birch reduction). This reagent, however, attacks most polar functional groups (except for carboxylic acids R.E.A. Dear, 1963 J. Fried, 1968), and their protection is necessary (see section 2.6). 

However, despite nearly 50 years of intense activity and progress, there are no commercially viable catalysts for the polymerization of acrylates or the controlled copolymerization of simple olefins with polar functional monomers. The development of a catalytic system capable of such controlled copolymerization would constitute a quantum advance in the plastics industry. 

In order to incorporate polar-functionalized olefins, the catalyst system must exhibit tolerance to the functionality as described above. Therefore, polar monomer incorporation by the Ni(II) catalysts is generally not observed. Traces of methyl acrylate can be incorporated by the Ni(II) catalyst only under low loadings of that monomer [85], Acrylamide has been incorporated after prior treatment with tri-isobutylaluminum to block the amide donor sites, although polymerization activities are still relatively low [86], A similar protection of Lewis-basic functionalities by the coactivator has been cited to explain the copolymerization of certain monomers by early transition metal systems as well [40],... 

The cationic Pd(II) catalysts exhibit effective copolymerizations of ethylene and other a-olefins with polar-functionalized comonomers, with the majority of insertions occurring at the ends of branches. Among the best tolerated monomers are those bearing fluorine or oxygen-containing functionalities, such as esters, ketones, and ethers. The copolymerization of ethylene and acrylates, attractive because the monomers are inexpensive and the copolymers exhibit unique physical properties, has been well-studied mechanistically [27,69], Examples of copolymerizations of ethylene and a-olefins with methyl acrylate are shown in Table 4. In general, the amount of comonomer incorporation varies linearly with its reaction concentration and... 

Recently, additional catalyst systems which are effective for the metathesis of olefins bearing polar functional groups have been revealed. Nakamura and co-workers found that either WC16 or (C2H50)2MoCl3 in combination with triethylborane were capable of converting c/s-9-octa-decenyl acetate to 1,18-diacetoxy-9-octadecene and 9-octadecene at the rather high temperature of 178°C (89). 

In summary, the metathesis of olefins substituted with polar functional... 

Styrene is slightly polar compared to ethylene and a-olefins. The lack of a strongly polar functional group allows styrene to undergo highly (>95-98% ) isoselective polymerization... 

As mentioned before, problems with monomers with functionalities with acid hydrogen have been encountered with some types of catalysts. Now, the direct incorporation of polar functional groups along the backbone of linear polymers made via ROMP is possible due to the development of functional group-tolerant late transition metal olefin metathesis catalysts (10). 

The relative insensitivity of this class of Ni catalysts to polar functional groups, and especially their low oxophilicity, is another important characteristic. This property has been exploited for the development of novel polymeric materials that might find new applications. For example, 1-hexene has been copolymerized with 6-(2-ureido-4-[lH]-pyrimidinone)hex-l-ene (30) to generate a new poly(olefin) elastomer (equation 7). The dimerization (through H-bonding) of the pyrimidinone moieties forms noncovalent crosslinks that bestow unique properties to the otherwise amorphous poly(l-hexene) matrix. 

The carbon-carbon double bond (olefin or alkene) is a structural feature on the border of framework and functionality. Unlike the carboxylic acid in 1 it is inside the skeleton of the molecule and involves no atoms except carbon and hydrogen. It has no polarity and yet it has the potential of producing highly polar functionality at two carbon atoms in a single reaction, as in the iodolactonisation to give 2 from 1. 

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