5-Norbomene-2-carboxylic acid

Although a large number of chiral dienophiles have been developed (Table 26.2), their ability to provide high asymmetric induction appears to be limited to specific dienes. However, there are some dienophiles that tolerate a wider variety of dienes including menthol derivatives,117 118 camphor derivatives,6 39 40 105 107-113 181 182 and oxazolidinones.120 165 183 184 It should be noted that even these auxiliaries would require an efficient recycle protocol for economic scale up. One exception is the use of sacrificial chiral oxazolidinones, which are relatively inexpensive. This approach has been used in the large-scale preparation of the base cyclohexane unit of Ceralure Bj.168 A procedure has been developed for the preparation of (75,25)-5-norbomene-2-carboxylic acid where the D-panta-lactone auxiliary can be recycled efficiently.185186... 

The concept of using an ester auxiliary which also contains a handle suitable for chelation was first disclosed in 1984/1985. Thus TiCU-promoted addition of cyclopentadiene to the acrylate of ethyl (S)-lactate (379) proceeded readily at -63 C to give (with a 39 1 endolexo preference) a 93 7 mixture of norbomenes (381a) and (382a), from which the major product (381a) was isolated by MPLC (Scheme 93, Table 23, entry 1). Mild saponification of adduct (381a) with LiOH in aqueous THF and purification via iodolactonization/elimination provided pure (l/ ,2/ )-5-norbomene-2-carboxylic acid. 

A second method for the synthesis of organometallic polynorbomenes containing a bound azo dye involved the reaction of T -chlorotoluene- n -cyclopentadienyliion complex 21 with bifunctional azo dyes to yield the azo dye-containing organoiron compounds, which wctc then further reacted with 5-norbomene-2-carboxylic acid (16) to form the azo dye functionalized norbomene monomers, 24, shown in Scheme 7.7. 

Reaction of complex 31 with 5-norbomene-2-carboxylic acid (16) yielded the organoiron monomer 32. ROMP of monomer 32 using Grubbs catalyst (18) gave... 

Bazan reported on the synthesis of pseudo-tetrablock copolymers comprised of ethene and 5-norbomen-2-yl acetate, using the initiator system (LiPr2)Ni(q -CH2Ph) (PMes) [(LiPr2) = 77-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino) propanamide] and 2.5 equivalents of Ni(cod)2 [bis(l,5-cyclooctadiene)nickel [121, 130, 131]. Square-planar nickel complexes with anionic P,0-chelate ligands were used by Goodall and coworkers for the co- and terpolymerization of norbomene and 5-norbomene-2-carboxylic acid ethyl ester with ethene [126]. 

A short synthesis of the carbocyclic analogue of S-phosphoribosyl-1-pyrophosphate from the known (C.R. Johnson et al.. Tetrahedron, 1984, 40, 1225) chiral ketone 72 has been described. Syntheses of carba-a-D-arabinofuranose and of the carba-nucleosides (+)-cyclaradine and (+)- caH>a>P-D-arabinofuranosyluraciI from key intermediate nitro-compound 73 have been reported. A short synthesis of Ohno s lactone, 74 in 54% overall yield from (+)-(lR)-e/u/o-5-norbomene-2-carboxylic acid, as a useful carbocyclic nucleoside precursor, has been reported." See Chapter 20 for the synthesis of carbocyclic tiazofurin and other carbocyclic nucleosides. 

FIGURE 2 H NMR spectrum of exo 5-norbomene-2-carboxylic acid in DMSO-d... 

As an example, when the photoacid generator triphenylsulfonium hexafluoro-antimonate is exposed to radiation, it decomposes to release the superacid hexafluoroantimonic acid in the resist film. While this photochemical reaction can occur at room temperature, the acid-catalyzed deprotection of the pendant t-butyl group of the resist polymer occurs at reasonable rates only at elevated temperature. It is therefore necessary to heat the resist film to an appropriate temperature (PEB) to provide the energy that is required for the acid-catalyzed deprotection of the t-butyl group of the ester, which in mrn affords the base-soluble norbomene carboxylic acid unit the isobutylene volatilizes. The extent of deprotection at constant temperamre is dependent on the dose of applied radiation. By monitoring the carboxylic acid OH stretch 3000-3600 cm and the ester carbonyl (C O) around 1735 cm acid carbonyl (C O) around 1705 cm , and ester (C-O-C) stretch around 1150 cm it is possible to determine by means of IR spectroscopy the extent of dose-dependent deprotection, as well as the influence of baking temperature on the extent of deprotection for each resist system. Doses ranging from 0 to 50 mJ/cm were applied to each resist system, after which they were baked at 120, 130, 140, and 150°C for 60 seconds and analyzed by FTIR. ... 

When the photoacid generator, triphenylsulfonium hexafluoroantimonate, is exposed to radiation, it decomposes to release the super acid, hexafluoroantimonic acid, in the resist film. While this photochemical reaction can occur at room temperature, the acid-catalyzed deprotection of the pendant r-butyl group of the resist polymer occurs at reasonable rates only at elevated temperature. It is therefore necessary to heat the resist film to an appropriate temperature (postexposure bake) to provide the energy that is required for the acid-catalyzed deprotection of the r-butyl group of the ester, which in turn, affords the base-soluble norbomene carboxylic acid unit isobutylene volatilizes. The extent of deprotection at constant temperature is... 

Kaita Sh, Matsushita K, Tobita M, Maruyama Y, Wakatsuki Y (2006) Cyclopentadienyl nickel and palladium complexes/activator system for the vinyl-type copolymerization of norbomene with norbomene carboxylic acid esters control of polymer solubility and glass transition temperature. Macromol Rapid Commun 27 1752-1756... 

Figure 29 Proposed 2/1 dimer structure formed by the reaction of TIBA and norbomene carboxylic acid.

Figure 8.16 Conversion of e Jo-5-norbomene-2-carbonitrile to the corresponding carboxylic acid using Alcaligenes faecalis Nit338...

Amphiphilic star-block copolymers can be prepared by adding a polycyclic diene such as 238 to a living diblock copolymer made by sequential ROMP of (i) the monomer in Table 9 with R = COOSiMe3, and (ii) norbomene. The trimethylsilyl ester groups are then converted to carboxylic acids by soaking the cast film of the polymer in water for 2-3 days to give a product with a hydrophobic core of polynorbomene and a hydrophilic outer layer126,502. 

Protonolysis occurs with retention of stereochemistry at the carbon atom originally attached to boron.Thus, by use of a deuteriated hydroborating agent e.g. 9-BBN-D) or of a deuteriated carboxylic acid, or both, deuterium atoms can be introduced at specific and predictable locations in a molecule. An example is the conversion of 2-norbomene into ej o,ej o-2,3-dideuterionorbomane (equation 56). ... 

Gust, Moore, Moore and coworkers covalent cartenoid-porphyrin-quinone molecular triads 55-60 contain a cyclized hydrogen bond within the quinone acceptor framework [143], The naphthaquinone moiety of 55 is fused to a norbomene system whose bridgehead position bears a carboxylic acid, which can hydrogen bond to an adjacent quinone. Photoinduced electron transfer from the porphyrin to the quinone leads to a marked p/fg increase of the latter, resulting in a fast proton transfer ( pt 10 s ) to form the semiquinone. Back electron transfer from the semiquinone is attenuated as a consequence of the proton-stabilized charge-separated species. This leads to a two-fold increase in the quantum yield of the charge-separated state of 55, as compared to those of the reference triads 56 and 57 (see Volume III, Part 2, Chapter 2). 

Norbomyl-2-exo-carboxylic acid. For the preparation of this acid by the hydrocarboxylation of norbomene at 50°, see Nickel carbonyl. 

Addition of carboxylic acids to alkenes (e.g., norbomene) is promoted by FeCls-AgOTf in refluxing 1,2-dichloroethane. Unsaturated carboxylic acids give y-lactones. ... 

Copper The catalytic activity of copper(II) triflate for cyclizations of alkenols or intermolecular additions of alcohols and carboxylic acids to norbomene has been reported [62, 63]. In dioxane at 80°C, high conversions were achieved at prolonged reaction times, and those were superior to those obtained with Lewis acids such as Yb(OTf)3, though the latter also displayed catalytic activity [62]. In a control experiment with triflic acid (10 mol%) only little product (29%) resulted with low stereoselectivity. However, it is now clear that this control experiment was flawed, as too much triflic acid and overly long reaction times had been applied. The previously mentioned study by Carpentier and coworkers on copper triflate catalyzed hydroaUcoxylations has established that Cu(OTf)2 decomposes to CuOTf and triflic acid when heated in organic solvents [50]. Triflic acid is catalytically active in hydroaUcoxylation at levels down to 0.1 mol%, if a polymerization inhibitor is present to prevent consumption of the olefinic substrate. Indeed, Cu (OTf)2 is an excellent reagent for releasing small amounts of triflic acid in this case, because the coreleased CuOTf acts as polymerization inhibitor for the acrylic substrate (Scheme 12) [50]. Other metal triflates like Sc(OTf)3 or Yb(OTf)3 displayed catalytic activity at the 1 mol% level in the reaction of Scheme 12. Additional experiments were presented to support the conclusion that triflic acid is the actual catalyst in this and other Lewis acid catalyzed hydroalkoxylations [50]. 

Poly(norbornene Sulfones) by Radical Polymerization. Cycloolefins such as norbomene copolymerize with SO2 in an alternating fashion by radical initiation at room temperature or even at 50 °C, reflecting their high ceiling temperatures (77). In order to avoid the use of a pressure bottle, however, we carried out the polymerization of norbomenes with SO2 at cryogenic temperatures. A partial list of poly(norbomene sulfones) we prepared is presented in Scheme V. All the polymers were prepared readily in high conversions but some of the polymers were not very soluble (pendant carboxylic acid, for example). This paper primarily discusses about the... 

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