Norbomene acid-catalyzed

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. ... 

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]. 

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... 

C. D. Smith, J. I. GavrUyuk, A. J. Lough, R. A. Batey, J. Org. Chem. 2010, 75, 702—715. Lewis acid catalyzed three-component hetero-Diels-Alder (Povarov) reaction of N-arylimmes with strained norbomene-derived dienophiles. 

BigeaulL J., Giordano, L., Buono, G. (2005). [2-1-1] cycloadditions of terminal alkynes to norbomene derivatives catalyzed by palladium complexes with phosphinous acid hgands. Angewandte Chemie, International Edition, 44, 4753-4757. 

Insertion of aUcynes into aromatic C-H bonds has been achieved by iridium complexes. Shibata and coworkers found that the cationic complex [Ir(COD)2]BF4 catalyzes the hydroarylation of internal alkynes with aryl ketones in the presence of BINAP (24) [111]. The reaction selectively produces ort/to-substituted alkenated-aryl products. Styrene and norbomene were also found to undergo hydroarylation under similar condition. [Cp IrCl2]2 catalyzes aromatization of benzoic acid with two equivalents of internal alkyne to form naphthalene derivatives via decarboxylation in the presence of Ag2C03 as an oxidant (25) [112]. 

There are two reports of an alkyl to aryl rhodium migration process. The first example was reported in 2000 by Miura [75], It was discovered that, upon reaction of phenyl boronic acid with norbomene under rhodium-catalyzed conditions, a merry-go-around type sequential alkylation occurred up to four times on the aromatic ring, resulting in a 1,2,3,4-tetranorbomylated benzene as the final product (Scheme 16). Mechanistically, this reaction involves an alkyl to aryl migration of rhodium. Thus, aryl rhodium intermediate 29, generated via an initial transmetalation step,... 

The amination of norbomene with aniline is catalyzed by [IrCl(C2H4)2L2] (L = PEta) which is converted into a catalytically active intermediate through loss of C2H4. The mechanism (Scheme 12) is supported by the independent synthesis and isolation of the complexes (A) and (B). The reaction becomes catalytic in the presence of a Lewis acid (ZnCl2) which promotes the formation of the cationic... 

The norbomene-catalyzed reaction has also been extended to synthesis of 2,6-dialkyl-1,1 -biphenyl 28 by 2,6-dialkylation of aromatic ring via palladacycles and Suzuki-Miyaura coupling. The reaction of phenylboronic acid (27), iodobenzene, and n-propyl bromide (excess) in the presence of norbomene (1) afforded 2,6-din-propyl-1-biphenyl (28) in 95 % yield via 29 and 30. 

Hydroaminations of alkenes have proven to be more challenging to develop than other hydroamination reactions, although some of the first hydroaminations were additions to alkenes. In 1971 Coulson reported the addition of secondary amines to ethylene catalyzed by RhClj. Additions of amides to ethylene and propylene have been published more recently by Widenhoefer, as shown in Equation 16.57, and the addition of aniline to norbomene was published by Milstein and Casakiuovo. Although the turnover numbers for the addition of aniline to norbomene were low, several important mechanistic findings resulted from this work were presented in Chapter 9 and are reviewed in Section 16.5.3.3. Additions of amines to ethylene, propylene, and norbomene are less complicated than additions to higher olefins because these alkenes cannot undergo isomerization to a less reactive internal olefin. Nevertheless, Brunet has reported additions of arylamines to ethylene and hexene catalyzed by platinum halides with acid additive in anionic liquid (Equation 16.58). ... 

Esterification. Add-catalyzed esterification of carboxylic acid with alcohol produces water as a coproduct. However, a greener method of esterification of carboxylic acid is via the addition of olefin, which does not produce any co-products and therefore, displays 100% atom efficiency. Proton-exchanged montmorillonite (H+-mont) can be used as a catalyst for addition reactions of carboxylic acids to alkenes (Fig. 7) (38)a). For example, the reaction of benzoic acid with norbomene in the presence of the H+-mont catalyst gave 2-benzoyloxynorbomane. Even with less-reactive simple alkenes, such as cyclopentene and cyclohexene, the corresponding esters were obtained in excellent yields. 

Catellani [61] reported a palladium/norbomene-catalyzed synthesis of heteroatom-containing o-teraryls from aryl iodides and heteroarenes (including indoles and pyrroles) through double C-H arylation. Fagnou s group [62] applied their own protocol (Pd(II)/Ag(I)/carboxylic acid) to achieve the direct arylation of azaindoles. Itami [63] demonstrated the first iridium-catalyzed C-H arylation of heteroarenes (involving indoles and pyrroles) with aryl halides. 

Miura and co-workers have reported a rhodium-catalyzed multiple alkylation of phenylboronic acid [34]. The reaction of a large excess of 2-norbomene (49) with phenylboronic acid (2m) in the presence of the [RhCl(cod) 2/dppp catalyst in toluene gave a mbcture of 1,2,3,4-tetra- (50m), 1,2,3-tri- (51m), and l,2-di(2-norbomyl)ben-zenes (52m) (Scheme 4.21). 

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