Norbomadiene derivatives

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

The final example of the intramolecular 1,3-dipolar cycloadditions of nitrile oxides is the formation of the norbomadiene-derived tetracyclic adducts 146, described by Tam and co-workers (240,241). The nitrile oxide 145, formed from 144 by dehydration, can in principle give rise to four different cycloaddition products (three [2,3]-cycloaddition products). In practice, only diastereomer 146 was obtained. The reaction was used on substrates with a variety of different substituents (R=H, Me, hexyl, Cl, Br, C02Me, CH2OMe), and in these cases, yields ranging between 66-89% were obtained (Scheme 12.48). 

The norbomadiene derivatives (157) undergo efficient ring closure to give the corresponding quadricyclanes (158). The ester functions of these products were elaborated by reduction and ether formation to provide a path to so-called tentacle molecules. 

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 ... 

Lewis-acid catalysis is effective in intermolecular as well as intramolecular Ziowo-Diels-Alder reactions. Thus, complex polycyclic compounds 93 have been obtained in good yield by the cycloaddition of norbomadiene-derived dienynes 92 by using cobalt catalyst, whereas no reaction occurred under thermal conditions [91] (Scheme 3.18). 

The radical cation of (163) can be formed by electron transfer photochemistry and in methanol addition products are formed. A study of the photochemical reactivity of some novel 3-phenylnorbomadienes has been reported. Bichromo-phoric norbomadiene derivatives have also been synthesized and studied photo-chemically. A study of the photoisomerization of some norbomadienes has been carried out within the constrained environment of P-cyclodextrin. The bichromophoric system (164) undergoes intramolecular electron transfer by a through-bond mechanism on irradiation. The transfer is from the benzidine... 

Square-pyramidal metallacycles are not observable at 25°C upon adding 7-oxa-norbomadiene derivatives to Mo(=CHMe2R)(=NAr)(OCMc2CF3)2 except as a transient red colour, rapidly changing to the characteristic orange colour of the living carbene complexes. However, the metallacycles can be observed at low temperature (Bazan 1991c). 

Sample Preparations. Figure 2 shows the chemical structures of NBD (norbomadiene) derivatives and other dyes used in this study. NBDA (norbomadiene dicarboxylic acid) and P(MMA-co-GMA-PNCA)(20) were supplied by Prof. Nishikubo of Kanagawa University. P(NBDA//wXDA) was synthesized as previously reported(2i). Dyes of DAAB (p-dimethylaminoazobenzene), FG540 ((E)-a-2,5-dimethyl-3-furylethylidene(isopropyl)succinic anhydride) and MAB (p-methoxyazobenzene) were of commercial purity. PMMA... 

In addition to the assembly of various carbocyclic and heterocyclic six-membered ring assembly, nickel-catalyzed [2+2+2] homo-Diels-Alder cycloadditions have been illustrated using norbomadiene derivatives (Scheme 3-30). Electron-deficient dienophiles undergo cycloadditions with norbomadiene using catalysts prepared from Ni(cod)2 and PPI13. Chemical yields and exo-selectivities are both generally high in these processes. 

In the case of symmetric polymers made from norbomadiene derivatives one approach has been to prepare polymers which have pendant groups containing chiral centres of a single, defined handedness [7]. 

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... 

Pd-catalyzed elimination reaction of norbomadiene derivatives gave the dienyl acetate by elimination of HOAc (Scheme 15). However, Pd-catalyzed elimination of dicarbonates of 1,4-butenediols gave 1,3-dienes by reductive elimination of dicarbonate. Reaction of d3-l,4-dimethoxycarbonyloxy-2-cyclohexene gave the reductive elimination product in 60% with the aromatic product by double elimination of acetic acid using triisopropy-Iphosphate. Irani-l,4-Dimethoxycarbonyloxy-2-cyclohexene did not give the reductive elimination product. 

Mo(OBu )(N(C 3PrV2>6)(=CHCMe2R) (R= Me. Ph) polymerise 7-oxabenzonorbomadiene and 2,3-endb-cu-diacetoxy-7-oxonorbaniene into polymers that have a narrow molecular weight distribution. Other norbomene and norbomadiene derivatives form stable metallacycles instead.3 >... 

Norbomenes and norbomadienes derivatives were S5mthesized by Diels-Alder condensation of cyclopentadiene and corresponding dienophile as a key reaction [3-6] ... 

NMR studies of the ROMP of certain 7-substitoted norbomadiene derivatives provided a remarkable example of a substituent-dependent re-gioselectivity. Scheme 16. 7-methyInorbomadiene [62] and 7-t-butoxynorbor-nadiene [77] were polymerised using a range of catalysts whereas the 7-Me derivative behaved in the expected manner with almost exclusive attack at the anti face of the molecule NMR spectra of the polymers are discussed below),... 

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... 

Multiblock polymeric networks are the logical extension of the homopolymer as it is essentially two or more homopolymers covalently attached in a linear fashion. For many applications, the result is rather simplistic in frmctionality. An early example of block copolymers used a titanacyclobutane to effectuate the polymerization of norbornene, norbomadiene derivatives, and cyclopentadiene into diblock or triblock hydrocarbon copolymers with PDIs of 1.08-1.14. The ROMP of cyclobutadiene using a tungsten catalyst followed by hydrogenation yielded polyethylene or instead of hydrogenation, it can be used to form diblocks and triblocks with norbomadiene." The ability to form block copolymers can be a test of the efficiency of a catalyst as was done with the third-generation Cmbbs catalyst by Stelzer in which oligomeric norbornyl monomers were used to synthesize homopolymers, diblocks. 

Norbornadienes Possessing Cationic Electron Withdrawing Groups Biphotochromic Norbomadiene Derivatives ... 

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