Arene complexes norbornenes

We have reported that norbornene monomers functionalized with arene complexes also undergo ring-opening metathesis polymerization to produce the corresponding cyclopentadienyliron-coordinated polynorbomenes. Scheme 13 shows the synthesis of polymers containing aromatic ether sidechains functionalized with organoiron moieties. ... 

In a further development of the norbornene/anihne OHA reaction, Salzer and coworkers used planar chiral arene-chromium-tricarbonyl-based diphosphines for the in situ formation of cis-trans mixtures of complexes 9 and 10 that gave enanti-oselectivities of 51% and 70%, respectively, at 333 K and with a 40-fold excess of naked fluoride , but activities were very low. In the same paper complex 6 was shown to be superior in both activity and enantioselectivity (64% ee) to the corresponding Josiphos compound 5 [15]. The activated N-H bond of benzamide was also stereoselectively added across the double bond of norbornene to afford N-benzoyl-e%o-aminonorbornane in up to 50% yield and 73% ee in the presence of 0.5mol% [IrCl((R)-MeO-bipheb)]2 at 373 K [16]. 

Allenylidene-ruthenium complex Ib readily promotes the ROMP of norbornene, much faster than the precursor RuCl2(PCy3)(p-cymene) [39] (Table 8.1, entry 1). The ROMP of cyclooctene requires heating at 80 °C (5 min), however a pre-activation of the catalyst allows the polymerization to take place at room temperature. The activation consists, for example, in a preliminary heating at 80 °C or UV irradiation of the catalyst before addition of the cyclic aikene, conditions under which rearrangement into indenylidene and arene displacement take place [39] (Table 8.1, entries 2,3). The arene-free allenylidene complexes, the neutral RuCl2(=C=C=CPh2)... 

The tungsten(II) carbonyl complex (CO)4W(/u.-Cl)3W(SnCl3)(CO)3 has been identified as a very effective catalyst for the hydroarylation of norbornene conducted in arene solution at room temperature. Norbornene adducts with benzene, toluene, p-xylene, and mesitylene have been isolated. On the basis of XH NMR monitoring of several catalytic reactions, a possible mechanism, involving coordination of norbornene to the W(II) atom and its activation, has been proposed.123... 

As an overall consequence, not only Pd complexes but also norbornene serve as catalysts. Furthermore, the sequential orf/zo-alkylation-vinylation of iodo benzene as a substrate even leads to ortho, ortho double alkylated vinyl arenes 27, representatives of 1,2,3-trisubstituted arenes that are not easily accessible by conventional methods (Scheme 9). 

A new three-component reaction incorporating an aryl iodide, an aryl bromide, and an acrylate to give ortho-aryl-substituted cinnamates 201 recently also developed by Catellani et al. (Scheme 8.48) [361], proceeds only in the presence of norbornene and involves an intermediate norbornylpalladium complex and palladation of an arene ring. 

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