Norbomene 7-oxanorbomene

Although the alkylidene complexes initiate the ROMP of functionalized norbomenes and 7-oxanorbomenes in aqueous solution quickly and completely in the absence of acid, the propagating species in these reactions often decompose before the polymerization reaction is complete. For example, in the ROMP of the water-soluble... 

Upon UV irradiation, complexes of the type [(j -arenei)Ru( / -arene2)] and [Ru(NCR)6] are transformed into active catalysts for the ROMP of norbomene and 7-oxanorbomene derivatives (Karlen 1995). 

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... 

Norbomene (Mi) has been copolymerized with a number of its derivatives and with 7-oxanorbomene derivatives (M2), using RuCls and other catalysts. The monomers are of comparable reactivity (ri = 0.5-2.6) and the behavioiu close to ideal (rir2 = 0.9-2.2) (Monakov 1995 Tlenkopatchiev 1995c). 

Studies of this kind fall broadly into two groups as indicated in Table 15.1. Those labelled P are mainly concerned with the effect of small quantities of acyclic olefin M2 on the MW, yield, and cis content of the polymer produced from the cyclic olefin Mi in this case the ratio [M2]/[Mi] is usually 0-0.05. Those labelled T involve the use of much higher proportions of M2 (with [M2]/[Mi] 0.5-2), with the object of producing telomers with well-defined end-groups, in some cases for synthetic purposes. For example, highly substituted cyclopentane and tetrahydro-fiiran derivatives can be readily made by the cross-metathesis of substituted norbomenes or 7-oxanorbomenes with hex-3-ene or l,4-dimethoxybut-2-ene catalyzed by ruthenium carbene complexes (Schneider, M.F. 1996). If the acyclic olefin is unsymmetrical and represented by Q Q, where Q and are the alkylidene moieties, three series of telomers may be produced, Q (Mi) Q, Q (Mi) Q, Q (Mi) Q, where ti is the number of Mi units. The lowest members of the series (n= 1) are dienes, and it is sometimes possible to deteet, separate, and identify the cc, ct, and tt isomers. 

Wathier, Stoddart, and Grinstaff reported using the Grubs catalyst to form high molecular weight polymers, poly(ethyl-5-norbomene-2-carboxylate) and poly(methyl-5-oxanorbomene-2-carboxylate) carrying ester functions. The preparations were illustrated as follows [185] ... 

A benefit of functionalized homopolymers is the ability to perform postpolymerization modifications. A norbomene bearing a methacroyl isocyanate efficiently underwent homopolymerization via ROMP to yield a cross-linked homopolymer, which upon ligand exchange with poly(methyl methacrylate) afforded a material with enhanced thermal stability over the original poly(methyl methacrylate). The preparation of an oxanorbomene derivative bearing a 1,2-bis (3-thienyl)cyclopentene photochrome followed by ROMP accessed a polymer capable of the same reversible photoisomerization as the monomer. 

These reactions can also be strongly biased by the choice of monomer and catalyst. The polymerization of substituted, polar 7-oxanorbomene derivatives with apolar tydoalkenes by GoughUn and Ilker afforded up to 98% alternating monomer utilizing G1 while the more active catalyst G2 yielded at best 85% of the desired pattern. Similarly, use of GOD or cydooctene enable > 90% alternation while this value plummeted to 40% when norbomene was used as the nonpolar monomer. ... 

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