Norbomadiene polymerization

Polymeric isoxazolines were prepared by cycloaddition of nitrile oxides to norbomadiene followed by ring-opening metathesis polymerization (ROMP) <06PLM3292 06MM3147>. 

A dry polymerization tube was charged with the step 1 product (0.28 mmol), 300 p,l THF, and 100 julI triethylamine and then treated with a solution of norbomadiene rhodium dichloride (0.028 mmol) dissolved in THF. The mixture was stirred at 30°C for 3 hours and was then poured into excess ethanol. The filtrate was separated by centrifugation and dried. After dissolving in benzene and freeze drying, the product was isolated having an Mn of 230,000 Da. 

In the Norsorex process, norbomadiene is polymerized by a ROMP type process. Polymers synthesized by ROMP have poor thermal stability and oxidative stability due to unsaturation of the main chain. They are used as thermoplastic resins or thermosetting resins. 

Much less is known about the ring-opening polymerization of norbomadiene. Surprisingly, OSCI3, a nonselective catalyst in the polymerization of norbomene, was found to yield an all-cis polymer.121... 

The reaction of the polymeric diene complexes, [RuCl2(diene)]u [diene = cod (1,5-cydooctadiene), nbd (2,5-norbomadiene)], with allylic Grignard reagents gives white bis(allylic) complexes, Ru(allyl)2(diene) (allyl = C3H5, 2-methylallyl), which contain asymmetrically bonded allyl ligands (Eq. 5.2) [10],... 

It should be mentioned that norbomadiene can be polymerized by various means, or that it can be metalated by -butyllithium (31). Finally, it must also be pointed out that the bromine derivatives are probably toxic (21). 

Another example of self-assembly of porphyrin-containing polymer was illustrated by Li et al.73 Polyacetylene functionalized with fullerene and zinc porphyrin pendant groups were synthesized by polymerizing the corresponding fullerene/porphyrin substituted alkyne monomers with rhodium(I) norbomadiene catalyst (Scheme 5.5).74 Polymers with different ratio of C60 and porphyrin were synthesized. The polymers showed photocurrent response when the thin films were irradiated with white light, which was due to the electron transfer from the photo-excited porphyrin to the C60 units. In addition, the copolymers aggregated into ellipse-shaped nanorod structures with a diameter of approximately 100 nm and a length of... 

The tungstacyclobutane complex formed by the addition of W(=CHCMe3) (=NAr)(OCMe3)2 to 2,3-bis(trifluoromethyl)norbomadiene at 0°C has been characterized at low temperature and, as expected, has the transoid structure and square-pyramidal geometry. It rearranges to the tungsten carbene complex trans double bond), but is unstable and does not polymerize the monomer smoothly (Bazan 1990). 

Tacticities have been determined for polymers of various derivatives of norbomene, norbomadiene and 7-oxanorbomene. Three methods have been used (i) by polymerizing single enantiomers of 5-, or 5,5-, or e rfo,exo-5,6-disubstituted derivatives, and determining whether the polymers have an HT (m) or HH/TT (r) stmcture, or both (m and r) (ii) by polymerizing 5,6-disubstituted derivatives in which the substituents contain a chiral centre of a single handedness, and... 

Grubbs-type initiators are well-defined ruthenium aUcylidenes. Compared to molybdenum- or tungsten-based Schrock catalysts, the reactivity of ruthenium-based Grubbs catalysts is somewhat different. In terms of polymer structure, ROMP of norbom-2-enes and norbomadienes using ruthenium-based systems generally results in the formation of polymers that, in most cases, predominantly contain frany-vinylene units. Polymerizations initiated by Grubbs-type initiators are best terminated by the use of ethyl vinyl ether, yielding methylidene-terminated polymers. 

Polynortricyclene forms by cationic polymerization of norbomadiene by a transamular polymerization. The reaction is best carried out below -100 C to prevent crosslinking. Two propagation paths are possible ... 

Polynortricyclene [116-118] forms by cationic polymerization of norbomadiene by a transanular polymerization. 

Terminal alkynes substituted with chiral substituents have been polymerized by using a rhodium catalyst, [RhCl(NBD)]2 (NBD = norbomadiene) [6]. As shown in Scheme 3, polymerization of a chiral (carbamoyloxy)phenylacetylene 4 forms a cis-substituted polyacetylene 5. Due to the bulkiness of the substituents, these polymers show a helical conformation with no extended conjugation in the polymer chain. These materials are potentially useful as enantioselective permeable membranes to separate racemic amino acids and alcohols in water or in methanol. They can be also used as chiral stationary phase for enantioselective high-performance liquid chromatography (HPLC) analysis. 

Ring-opening metathesis polymerization (ROMP) has been used to prepare unsubstituted PPV via a soluble precursor. Substituted paracyclophan-l-ene (9) (24) and norbomadiene derivatives (10) (25) have been used as monomers, with... 

Tabata, M. Sadahiro, Y Yokota, K. Kobayashi, S. Formation of columnar from poly(p-methylethynylbenzene) polymerized using [Rh(norbomadiene)Cl]2 as a catalyst. Polym. J. 1996, 35, 5411-5415. 

Opstal, T., Couchez, K., Verpoort, F., Easily acessible ring opening metathesis and atom transfer radical polymerization eatalysts based on arene, norbomadiene and cyclooctadiene ruthenium eomplexes bearing Schiff base ligands, Adv. Synth. Catal. 2003,345 393—401. 

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