Norbornane-based

Relative to 7)/ for hole transfer through a single staggered alkane chain, norbornane-based bridges, characterized by two parallel alkane chains (relays linked by single... 

Norbornane-based bridge (two cross-linked alkane chain relays). 

A valid question which may be posed in connection with the methionine example is whether the initially oxidized sulfur couples only with nitrogen or possibly also with an oxygen from the carboxylate function. An answer to this was provided by synthesis of two norbornane-based stereo isomers in which the amino and carboxylate groups where fixed in their position relative to sulfur. 165 The respective transients 20 and 21 formed upon oxidation exhibit maxima at 400 and 340 nm and lifetimes of about 1 and 25 p,s, respectively. These data clearly speak for an S. .N coupling in the methionine system. Furthermore, 20 decarboxylates directly, while 21 rather appears to deproto-nate (at carbon adjacent to sulfur). 

Exo-endo additions of organic azides to the norbornene skeleton and other bridged bicyclic systems can be easily differentiated from the NMR spectra of the adducts. The endo protons (exo adducts) of the norbornane do not couple with the bridgehead hydrogens.386 The endo protons in position 3a and 7a of adduct 65 exhibit an AB spectrum. The lack of coupling with the bridgehead protons is a result of a dihedral angle of 82°.25,96 Based on this, the exo form of cycloadduct 66 exhibits symmetrical doublets centered at 8 4.60 and... 

Cp(CO)2Cr]5P10 (204) is based on a norbornane framework with additional P and P2 units attached, whereas in [(CpM4E)Rh]4Pi0 (205) it is structurally related to dihydrofulvalene. The norbornane structure also appears in [Ni P Bu3 2]4P14 (206), where two P7 units are connected. 

Using the methodology previously developed by Stella and coworkers22 and by Wald-mann and Braun23 to synthesize 2-substituted aza-norbornanes (see Section II.C), Ander-sson and coworkers prepared chiral lithium amide 1824,25. This chiral base has been reported to rearrange several epoxides in up to 98% ee in the absence or presence of high concentrations of DBU (Scheme 13). 

The synthesis and properties of poly(imide-siloxane) polymers and copolymers based on 5,5 bis(lyly3,3-tetramethyl-l,3-disiloxane-diyl)norbornane dicarboxylic anhydride are described. High-molec-ular-weight thermoplastics and elastoplastics were prepared readily in solution from aromatic diamines, organic dianhydrides, and this unique anhydride-terminated siloxane. The thermal and mechanical properties of a variety of copolymer compositions are described. Average siloxane block length and overall siloxane content had the greatest effect on these properties. 

The polymers and copolymers described in this chapter were derived fi"om the novel anhydride-terminated disiloxane, 5,5 -bis(l,l,3,3-tetra-methyl-1,3-disiloxanediyl)norbornane-2,3-dicarboxylic anhydride (DiSiAn) (14). Both siloxane-polyimide polymers and copolymers based on DiSiAn and its polysiloxane derivatives were investigated. This chapter describes the synthesis, characterization, and physical properties of these materials. 

The H-H bonding interaction is ubiquitous and has been found in a number of systems. The earliest experimental account I am aware of reporting unusually short intramolecular H- H distances is that of Ernier and Mason [42]. These authors find H- -H distances as short as 1.754(4) A and 1.713(3) A between neighbouring bridgehead hydrogen atoms in fused norbomenes based on low temperature neutron diffraction experiments [42]. Even shorter H- -H distances were suggested in another norbornene derivative on the basis of an X-ray diffraction determination (Jr h = 1-62 A) [49]. While the latter result awaits confirmation by neutron diffraction, it still indicates that norbornene or norbornane derivatives are candidates for very short, perhaps the shortest, intramolecular H- H distances. The molecular graph of the parent compound in this series (exo, exo-tetracyclo[6.2.1.1 .0 ]dodecane) obtained at the... 

The intermediacy of palladacycles in the reaction of bromobenzene with norbornene in the presence of Pd(PPh3)4 as catalyst and KOAc as a base in anisole as solvent was initially suggested by the isolation, among other products, of two compounds (Eq. 9), the former resulting from norbornene insertion into an alkylpalladium bond, the latter clearly deriving from palladium migration from the alkyl to the aryl site and double norbornene insertion. In both cases the termination step involved p,y-C-C bond cleavage followed by P-H elimination. The stereochemistry of the norbornane unit invariably was exo [19]. 

K. Kojio, S. Nakashima and M. Furukawa, Microphase-separated structure and mechanical properties of norbornane diisocyanate-based polyurethanes . Polymer, 2007, 48, 997-1004. 

Several models of this heme enzyme are based upon substituted porphyrins. For example, compound i (oxidized Fe in porphyrin ligand shown) catalyzes the oxidation of norbornane to norboran-2-ol with iodosobenzene... 

Since the technology is still developing, the industry has not yet focused its choice on one or two leading organo-bromine compounds. Rather, many manufacturers and many users of these flame retardants report serious interest in a wide variety of structures. Those most frequently mentioned in the technical literature, in approximate order of importance, are [2, 19, 21, 22, 25, 26], as follows decabromo diphenyl oxide, ethylene bis(tetrabromo phthalimide), tetradecabromo diphe-noxy benzene, ethylene bis(dibromo norbornane dicar-boximide), octabromo diphenyl oxide, hexabromo cyclo dodecane, tetrabromo dipentaerythiitol. In Europe, the organo-bromine compounds mentioned are quite different, mostly based on ethers of tetrabromo bisphenol A and while Europeans are more concerned about possible toxicity, paradoxically they are more likely to use polybrominated biphenyls, which would be taboo in the US [2, 28]. 

A sequence of Cu(I)-catalyzed [2 + 2]-photocycloaddition-cyclobutyl carbinyl cation rearrangement has been employed for the construction of novel carbocyclic compounds. Thus, cycloaddition of the dienol 40 to the hydroxymethyl cyclobutane 41 followed by solvolysis of its tosylate 62 afforded the triquinane 63 after reduction (Scheme 19). An efficient route to ex -l,2-polymethylene-7-hydroxy norbornanes 66 has also been developed based on this protocol. Photocycloaddition of an epimeric mixture of the dienols 64 to 2-hydroxybicyclo[3.2.0]heptanes 65 followed by treatment with trifluoro-acetic acid (TFA) affords the 7-hydroxynorbomanes 66 in overall good yields. 

If additional side chains (other than methyl or methylene groups) are present naming is based on the respective trivial names. Other substitution products of these skeletons are treated as norcarane, norpinane, and norbornane derivatives. 

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