Catalyzed oxidative coupling

Palladium-catalyzed oxidative couplings of aromatic compounds with alkenes in air lead to cinnamate products with TONs attaining 280 (Equations (66) and (67)).67,67a,67b... 

A molybdenum-mediated oxidative coupling of aniline 1 with cyclohexene 2a provides carbazole 3. Alternatively, the same overall transformation of aniline 1 to carbazole 3 is achieved by iron-mediated oxidative coupling with cyclo-hexa-1,3-diene 2b or by palladium-catalyzed oxidative coupling with arenes 2c. The use of appropriately substituted anilines and unsaturated six-membered hydrocarbons opens up the way to highly convergent organometallic syntheses of carbazole alkaloids. 

In recent years, numerous applications of such peroxidase-catalyzed oxidative coupling of phenols and aromatic amines have been reported (Table 7). These peroxidase-catalyzed biotransformations lead to modified natural products with high biological activities [110-118]. Several examples have also been described for the oxidative coupling of phenols with peroxidases and other oxidative enzymes from a variety of fungal and plant sources as whole cell systems... 

Our second approach for the total synthesis of carbazoquinocin C (274) uses the palladium(II)-catalyzed oxidative coupling of aniline (839) and 2-methoxy-3-methyl-... 

In addition to the aforementioned total syntheses. Shannon et al. observed the formation of an N-C3-linked dimer during the transformation of a 3-bromocarbazole to a 3-cyanocarbazole by reaction with copper(I) cyanide in DMF under reflux (668). Harrity et al. reported the synthesis of non-natural (+ )-N,N -dimethylbismurrayafoline A via a chromium-mediated benzannulation, followed by a palladium-catalyzed oxidative coupling reaction (669). 

Propylene oxide is one of the raw materials used to manufacture rubbery and crystalline polyepoxides. R. J. Herold and R. A. Livigni describe propylene oxide polymerization with hexacyanometalate salt complexes as catalyst. Polyphenylene oxide is made by copper catalyzed oxidative coupling of 2,6-dimethylphenol. G. D. Cooper, J. G. Bennett, and A. Factor discuss the preparation of copolymers of PPO by oxidative coupling of dimethylphenol with methylphenylphenol and with diphenylphenol. 

Piccolo, A., Cozzolino, A., Conte, P., and Spaccini, R. (2000). Polymerization of humic substances by an enzyme catalyzed oxidative coupling. Naturwissenschaften 87, 391-394. 

Tsuji, J. Nagashima, H. Palladium-catalyzed oxidative coupling of aromatic compounds with olefins using tert-butyl perbenzoate as hydrogen acceptor. Tetrahedron 1984, 40, 2699-2702. 

C-H activation can be used to generate carbazoles from N-aryl anilines by palladium catalyzed oxidative coupling (Scheme 3) [12]. Although this is a powerful method, it is ultimately limited by the fact that more heavily substituted N-aryl anilines may not couple selectively, leading to the formation of more than one product. 

Scheme 3. Formation of carbazoles via palladium catalyzed oxidative coupling.

Wacker reactions, which is why we refer to them here [12, 15-17]. Finally, the general concept of a Wacker reaction could be regarded as the palladium-catalyzed oxidative coupling of heteronucleophiles and olefins, and this can obviously be extended to nitrogen nucleophiles and others [18] conversely, the principle of the Cu(I)/Cu(II)/02 reoxidation system for Pd(0) can be applied to other oxidation reactions (for example that of CO to C02), but the present overview is limited to sp2-C-H activation in olefins. 

The industrial synthesis of vinyl acetate [14] via palladium-catalyzed oxidative coupling of acetic acid and ethene using direct 02 reoxidation has already been mentioned (Scheme 3, d). Some NaOAc is required in the reaction medium, and catalysis by Pd clusters, as alternative to Pd(II) salts, was proposed to proceed with altered reaction characteristics [14]. Similarly, the alkenyl ester 37 (Table 5) containing an isolated vinyl group yields the expected enol acetate 38 [55] whereas allylphenol 39 cyclizes to benzofuran 40 with double bond isomerization [56]. 

In the presence of bulky groups, such as in 3,5-di-ferf-butylquinone, the quinone is stable and can be isolated, but in most cases, it easily undergoes other reactions, such as Michael addition by nucleophiles present in solution, including the catechol itself. On the other hand, in some cases, the substrate oxidation can be driven to selected products [44], as in the synthesis of neurotrophic americanol A and isoamericanol by HRP-catalyzed oxidative coupling of caffeic acid [45] (Fig. 6.3b). 

Matsumoto K, Takahashi H, Miyake Y, Fukuyama Y (1999) Convenient syntheses of neurotrophic americanol A and isoamericanol A by HRP catalyzed oxidative coupling of caffeic acid. Tetrahedron Lett 40 3185-3186... 

Bodtke A, Pfeiffer WD, Ahrens N et al (2005) Horseradish peroxidase (HRP) catalyzed oxidative coupling reactions using aqueous hydrogen peroxide an environmentally benign procedure for the synthesis of azine pigments. Tetrahedron 61 10926-10929... 

Bollag JM (1992) Enzymes catalyzing oxidative coupling reactions of pollutants. In Sigel H, Sigel A (eds) Metal ions in biological systems, vol 28. Taylor and Francis, UK... 

Huang Q, Weber WJ Jr (2004) Interactions of soil-derived dissolved organic matter with phenol in peroxidase-catalyzed oxidative coupling reactions. Environ Sci Technol 38 338-344... 

Touring the last decade, catalyzed oxidative coupling has gained wide-spread interest as a novel and general polymerization method. Various polymer systems of scientific and commercial interest have been prepared by this novel technique. Such polymer systems include polyphenylene oxides) (9, 13, 25), of which poly(2,6-dimethylphenylene oxide) (PPO) is produced commercially polyphenylenes (21) poly-... 

In the last few years, the catalyzed oxidative coupling of primary aromatic diamines has been investigated extensively in our laboratories (1, 2, 3) and also by Kotlyarevskii (19, 20, 30). Results of these investigations are reviewed in this chapter as well as the properties of the class of aromatic azopolymers. 

Oxidative Coupling Reaction. Catalyzed oxidative coupling of primary aromatic diamines with oxygen as the oxidant yields linear polymers according to the following scheme ... 

Catalyzed oxidative coupling is generally applicable to simple primary aromatic diamines as well as to diamines of a complex structure. The scope of the reaction is exemplified by some of the polymers prepared ... 

Aromatic Azopolymers. Through the described catalyzed oxidative coupling of primary aromatic diamines a great variety of aromatic azopolymers has become easily accessible. Therefore, an investigation of their properties in bulk as well as fabricated form seemed warranted. 

As shown in recent investigations, catalyzed oxidative coupling of organic molecules provides a new and general route to a variety of hitherto only difficulty accessible polymer systems. While the literature on oxidative coupling reactions in polymer synthesis is already rather extensive, by further investigations of this reaction concept, particularly studies of the catalysis involved, oxidative coupling promises to rival conventional condensation and addition polymerization in importance. 

A successful ruthenium-catalyzed oxidative coupling and subsequent cyclization between 2-aminobenzyl alcohol and secondary alcohols in the presence of KOH and 1-dodecene leading to quinolines has been reported <03T7997>. After optimization of conditions, yields were fair to good. The reaction is widely applicable to a large series of 2-substituted quinolines. 

Ito and his coworkers have reported that palladium-catalyzed oxidative coupling reactions of Grignard reagents in the presence of V-substituted isocyanide dichloride afford diynes (equation 17). Isocyanide dichloride may serve as a reoxidant of the palladium catalyst in this sequence via a catalytic cycie. In addition Kiji and his coworkers have described the oxidative coupling of phenylacetylene by a Pd-Cu catalyst in the presence of 4-iodo-(3//) phenothiazin-3-one. ... 

Peroxidase-catalyzed oxidative coupling of phenols proceeds rapidly in aqueous solutions, furnishing oligomeric compounds. However, mixtures of organic solvents and water are used to better control the quality of the polymer. 

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