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Carbon Mizoroki-Heck reaction

Carbon-carbon bond formation reactions and the CH activation of methane are another example where NHC complexes have been used successfully in catalytic applications. Palladium-catalysed reactions include Heck-type reactions, especially the Mizoroki-Heck reaction itself [171-175], and various cross-coupling reactions [176-182]. They have also been found useful for related reactions like the Sonogashira coupling [183-185] or the Buchwald-Hartwig amination [186-189]. The reactions are similar concerning the first step of the catalytic cycle, the oxidative addition of aryl halides to palladium(O) species. This is facilitated by electron-donating substituents and therefore the development of highly active catalysts has focussed on NHC complexes. [Pg.14]

Other successful examples of catalysts containing NHC ligands are found in palladium- and nickel-catalyzed carbon-carbon bond formations. The catalyst development with these metals has focused in particular on Heck-type reactions, especially the Mizoroki-Heck reaction itself [Eq. (42)] and various cross coupling reactions [Eq. (43)], e.g., the Suzuki-Miyaura reaction ([M] = and the Kumada-Corriu reaction ([M] = MgBr). " Related reactions like the Sonogashira coupling [Eq. (44)]326-329 Buchwald-... [Pg.42]

Bulky ligands as above have also proved to be effective in other palladium-catalyzed reactions of aryl halides, e.g., amination [16-19], Suzuki-Miyaura reaction [20-22], Mizoroki-Heck reaction [23, 24], Migita-Kosugi-Stille reaction [25], and aryloxylation and alkoxylation [26-28] as well as the reaction with various carbon nucleophiles as described below. The ligands are considered to enhance both the initial oxidative addition of aryl halides and the reductive elimination of products [29, 30]. The effectiveness of the commercially available simple ligand, P(f-Bu)3, was first described for the amination by Nishiyama et al. [16]. [Pg.214]

Pd-doped organic and carbon aerogels containing between 20 and 40 wt% Pd were demonstrated to be good catalysts in the Mizoroki-Heck reaction of iodobenzene with styrene and 3-butene-2-one in liquid phase to yield franv-l,2-diphenylethylene and frani-4-phenyl-3-butene-2-one, respectively [52], Finally, Eu-doped organic and carbon aerogels were active as catalysts in two Michael addition reactions the reaction of ethyl 2-oxocyclopentanecarboxylate with 2-butenone and with cyclopentenone. Moreover, these catalysts could be recovered and reused [53],... [Pg.393]

Table 5.4 Supported Pd catalysts on carbon tested in Mizoroki-Heck reactions. Table 5.4 Supported Pd catalysts on carbon tested in Mizoroki-Heck reactions.
The Mizoroki-Heck reaction, a palladium-catalyzed coupling of olefins with aryl or vinyl halides/triflates, is a powerful method for carbon-carbon bond formation. " " High efficiency is usually obtained only by starting from expensive aryl iodide (or bromide) or by using a fairly large amount of catalyst. Improvement of the catalytic activity as well as recovery and recycling of the catalyst is needed. [Pg.39]

The Suzuki-Miyaura cross-coupling reaction is a standard method for carbon-carbon bond formation between an aryl halide or triflate and a boronic acid derivative, catalyzed by a palladium-metal complex. As with the Mizoroki-Heck reaction, this cross-coupling reaction has been developed in ionic liquids in order to recycle and reuse the catalyst. In 2000, the first cross-coupling of a halide derivative with phenylboronic acid in [bmim] [BF4] was described. As expected, the reaction proceeded much faster with bromobenzene and iodobenzene, whereas almost no biphenyl 91 was obtained using the chloride derivative (Scheme 36). The ionic liquid allowed the reactivity to be increased, with a turnover number between 72 and 78. Furthermore, the catalyst could be reused repeatedly without loss of activity, even when the reaction was performed under air. Cross-coupling with chlorobenzene was later achieved - although with only a moderate yield (42%) - using ultrasound activation. [Pg.43]

Supported catalysts involving palladium on carbon and dendrimer-encapsulated palladium and a polymer-supported phosphine palladium catalyst have facilitated C-C coupling reactions in SCCO2. Polymer-tethered substrates or amine bases have also been successfully used for the Mizoroki-Heck and Suzuki-Miyaura reactions in SCCO2. For example, REM resin underwent a Mizoroki-Heck reaction with iodobenzene to yield, after cleavage, ( )-methyl cinnamate 48 (74%) (Scheme 88). It is assumed that SCCO2 acts as a good solvent that swells the polymers and exposes reactive sites. [Pg.166]

This hitherto unknown reaction has attracted attention as a potentially important method for carbon-carbon bond formation. Now all reactions which proceed via insertion of alkenes and also alkynes to the arylpalladium intermediates 1 (Scheme 3.1) and the alkenylpalladimn 14 (Scheme 3.5) are called Mizoroki-Heck reactions or Heck reactions (abbreviated to HR in this chapter). A number of reviews have already been published [6]. The reaction is certainly the most useful and versatile method of carbon-carbon bond formation involving sp carbons. [Pg.111]

In the last decade, a lot of attention has been paid to environmental aspects. As to the Mizoroki-Heck reaction, environmentally benign media currently involved in the design of catalytic systems encompass supercritical carbon dioxide (scCOa), fluorous systems, water and aqueous systems, solvent-free systems [66]. In this context, it should be noted that the so-called solvent-free reactions are actually not literally such, but are performed in media composed of substrates and often liquid amine. This was described as early as in 1972 by Heck himself [2, 8] (microwave heated version [53]). Amines are good coordinating solvents during the reaction, the amine is transformed into amine salt, which, being a major constituent or reaction mixture in the absence of a true solvent, adds to the net media polarity. [Pg.64]

Haneda, S., Okui, A., Ueba, C. and Hayashi, M. (2007) An efficient synthesis of 2-arylimidazoles by oxidation of 2-arylimidazolines using activated carbon-02 system and its application to paUadium-catalyzed Mizoroki-Heck reaction. Tetrahedron, 63, 2414—7. [Pg.128]

It is vital to control the itt-complex formation and insertion steps in order to direct the regioselectivity of the Mizoroki-Heck reaction, in which the organic R group will be either added to the internal carbon of the monosubstituted alkene, yielding an a-product, or the terminal, providing trans- or cw-/6-products (Figure 3.1, steps 2-4 and Figure 3.2) [16,41]. [Pg.135]

Mizoroki-Heck cyclization of 198 was part of the studies towards the total synthesis of taxol (224) (see Scheme 5.38) by Danishefsky and coworkers [84] (198 199, Scheme 5.35). The strained seven-membered ring is formed in the presence of the hydroxyketone moiety in 52% yield and unconsumed 198 was re-isolated quantitatively. Danishefsky and coworkers [85] employed the high-yielding Mizoroki-Heck reaction of200 to assemble the bridged carbon skeleton in 201, an intermediate en route to the synthesis of CP-225,917 (202) and related CP-263,114 (not shown), which are squalene synthetase and famesyl transferase inhibitors (200 201). [Pg.204]

Since the early reports by Mizoroki, Heck and others, allylic alcohols 1 have been elusive substrates in the Mizoroki-Heck reaction (Figure 7.4) [5], When an insertion of ArPdX to C=C results in an organopalladium intermediate with palladium on the j8-carbon of allylic alcohol, which is often the case, there are hydrogen atoms available at the a- (Ha) and y-carbon (H ) in the subsequent 8-elimination step (Figure 7.4). It has been known from the early days that the treatment of allylic alcohol (1) with iodobenzene under typical... [Pg.262]

There are only a few examples so far where a Mizoroki-Heck reaction has been combined with a palladium(0)-catalysed nucleophilic substitution. Most of them make use of an amine as the nucleophile in the substitution of the 7r-allylpalladium(II) complex formed after the initial Mizoroki-Heck reaction however, there are also examples for the use of carbon nucleophiles. In an example, Weinreb and coworkers [64] described a three-component process consisting of a vinylbromide, an alkene and malonate ester as the nucleophile forming two new C—C bonds consecutively. Earlier, Larock et al. [65] had described a similar transformation. [Pg.300]

For recent reviews on the Mizoroki-Heck reaction, see (a) Alonso, F., Beletskaya, I.P. and Yus, M. (2005) Non-conventional methodologies for transition-metal catalysed carbon-carbon coupling a critical overview. Parti theHeckie ction.Tetrahedron,61,11771-835 (b) Erase, S. and de Meijere, A. (2004) Cross-couphng of organyl halides with alkenes the Heck reaction, in... [Pg.378]

The standard Mizoroki-Heck reaction is the substitution of a vinylic hydrogen by an alkenyl or aryl group catalysed by palladium(O) complexes (Scheme 11.1). Since its discovery in 1968 by Heck [1-3], this elaboration of substituted alkenes by direct C-C bond formation at the vinylic carbon centre has evolved into a synthetic transformation whose potential has only recently been exploited in the key steps of many total syntheses (Chapter 16) [4]. This recent exploitation has been due to a better understanding of the proper choice of reactants, solvent, base, additives, catalyst precursor and ligands necessary for optimal reaction conditions. [Pg.405]

Gedanken and coworkers [194] exploited power ultrasound to generate in situ amorphous-carbon-activated palladium metallic clusters that proved to be a catalyst for Mizoroki-Heck reactions (without phosphine ligands) of bromobenzene and styrene (yield to an appreciable extent of 30%). The catalyst is stable in most organic solvents, without showing any palladium powder segregation, even after heating them to 400 °C. [Pg.518]

Kayaki, Y., Noguchi, Y. and Ikariya, T. (2000) Enhanced product selectivity in the Mizoroki-Heck reaction using a supercritical carbon dioxide-liquid biphasic system. Chem. Commun., 2245-6. [Pg.527]

The lack of efficient methods for enantiocontrolled construction of tertiary and quaternary carbon stereocentres largely inspired the discovery and development of the asymmetric Mizoroki-Heck reaction [3], Shibasaki and coworkers [4] and Overman and coworkers [5] described the first catalytic asymmetric intramolecular Mizoroki-Heck reactions in 1989. Following these initial reports, research efforts worldwide led to enormous improvements... [Pg.533]


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See also in sourсe #XX -- [ Pg.140 ]




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