Norbomadiene derivatives 7-substituted

In Scheme 2.210, possible variants of intramolecular 1,3-dipole cycloaddition of norbomadiene derivatives with 2-substituted norbomadiene-tethered nitrones are presented. 

The incorporation of sulphonyl groups does not inhibit the cyclization process as demonstrated by Gleiter and Ohlbach, who have reported the efficient synthesis of the quadricyclane 252 by irradiation of the norbomadiene derivatives 253. A study has also been made of the sulphonyl-substituted norbomadiene derivatives 254 ... 

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... 

The exact control of polymer microstructures (e.g., tacticity and double-bond configuration) resulting from the ROMP of substituted norbomenes and norbomadienes is essential for the development of polymers with well-defined physical properties. Norbomene and norbomadiene-derived polymers could be accessed with... 

The preparation of norbomadiene-fused thiophene (17) involved a double-Wittig reaction of 1,2-dione 15 with the bis-ylide derived from phosphonium salt 16 <99BCSJ1597>. The effect of the fused heteroaromatic ring of 17 (neighboring group participation) on electrophilic substitution of the norbomadiene ring was examined. 

The photoisomerisation kinetics and other properties of the 1 1 inclusion complexes formed between aromatic derivatives of norbomadiene and P-cyclo-dextrin have been measured." (S)- or (R)-2-Chloropropiophenone affords partially racemised (S)- or (R)-2-phenylpropionic acid respectively by a photo-induced rearrangement via what is probably an ion or radieal intermediate," and (Z)-N-substituted benzoyl-a-dehydrophenylalanines such as (7) are photo-isomerised to 1-azetidine derivatives (8) by a 1,3-acyl migration. Irradiation of 9,9 -bifluorene-9,9 -diol (9) gives a mixture of fluoren-9-one and spiro[9H-fluorene-9,9 (10 -H)-phenanthren]-10 -one (10) whose composition is solvent dependent with the more polar solvents favouring (10). Laser flash photolysis shows the presence of two transients, one of which can be identified with the 9-fluorenyl cation (11), and which originates from photoheterolysis of the diol (9). There is also evidence to support the view that unimolecular rearrange-... 

Triorganylphosphane-modified palladium(O) compounds catalyze the codimerization of methylenecyclopropane with ethene, norbornene, dicyclopentadiene or norbomadiene to give substituted methylenecyclopentane derivatives. Here, in all cases, the three-membered ring is opened between C2 and C3. " ... 

Investigations have also examined the photochemical outcome of the inclusion of other aromatic substituents onto the norbornadienes. Examples of this are the direct and sensitized irradiation of the naphthyl-substituted derivatives 249 that brings about cyclization to 250. Sensitization of the cyclization with ketones such as benzophenone leads to a much cleaner reaction. Biacetyl has also been used as the sensitizer . Cyclization also occurs with the norbomadiene 251 2. 

Protection of C—C double bonds. The olefinic ligand of this cationic complex can be exchanged when heated above 20° with an excess of certain other olefins. Nicholas has used this property for protection of C—C double bonds, since the olefins can be regenerated by treatment of the complex with sodium iodide in acetone. The method is particularly useful for selective protection of dienes and polyenes. For example, the complex of norbomadiene undergoes electrophilic additions without isomerization to nortricyclane derivatives (equation I). The complex coordinates selectively with the less substituted and/or... 

The following hydrocarbons have been successfully substituted for 1,5-cyclooctadiene in this procedure to yield the corresponding dichloro(olefin)platinuin(II) derivatives 13,5,7-cyclooctatetraene, dicyclopentadiene (3a,4,7,7a-tettahydro-4,7-metbanoindeneX and bicydo[2.2.1]hepta-2,S-diene (2,S-norbomadiene). 

One may, by careful choice of monomer, study the potential of different catalysts to behave in a stereoselective or regioselective manner. Thus, with a symmetrical monomer such as norbomene [58], norbomadiene [59] or their 5,6 [60] or 7-substituted derivatives [61,62] we have obtained polymers with a variety of cis main chain double bond contents and distributions. In a number of the 7-substituted examples, fine structure on certain NMR resonances is observed which is attributable to tacticity effects. Conversely, one may use the unsymmetrical monomers such as 1-substituted derivatives [63] and delineate the propensity of the different catalysts to regioselectivity, which manifests itself as head-tail bias in the polymer. 

Similar micro structures are obtained when norbornene is replaced by norbomadiene. 5-and 6-substituted norbornene derivatives when polymerized by ROMP give more complex micro structures (Figure 11). By ROMP it is possible, more easily than by Ziegler-Natta catalysts, to polymerize norbor-nenes with polar substituents such as carbomethoxy, carboethoxy, or trifluoromethyl groups. " ... 

A catalytic asymmetric cycloaddition reaction between norbomadiene and methylenecyclopropane can also be achieved in the presence of a [Ni(cod)2]-(—)-benzylmethylphenylphosphine catalyst to give the cycloadduct (72) in an optically active form. This reaction may proceed via a metallocyclopentane intermediate. The reactions of methylenecyclopropane with [Ni(cod)2l-phosphine systems do not appear to involve cleavage of the three-membered ring. However, the bis(acrylonitrile)nickel-catalysed cycloaddition reaction of methylenecyclopropane with methyl acrylate, which yields 3-methoxy-carbonylmethylenecyclopentane (73), does involve C—C bond cleavage. Reaction with the deuterium-substituted compound CHD=CDC02Me gives the cyclopentane derivative (74). An intermediate of the type (75) may be involved in this reaction. 

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