Oxidative coupling of benzenes

Rhodium complexes catalyze the oxidative coupling of benzene with ethene to produce styrene directly.45,45a,45b Using Rh(ppy)2(OAc) (ppyH = 2-phenylpyridine), the reaction of benzene with ethene in the presence of 02 and Cu(OAc)2 in benzene and acetic acid at 180 °C gives styrene and vinyl acetate in 77% and 23% selectivities, respectively. 

Oxidative coupling of benzenes with , p- unsaturated aldehydes by... 

OXIDATIVE COUPLING OF BENZENES WITH a, fi- UNSATURATED ALDEHYDES BY Pd(OAc)2/HPMoV /O2 SYSTEM... 

The alkene arylation reaction has been extensively studied by Moritani and coworkers462 and by Heck.463 An interesting application of this chemistry is the synthesis of styrene from the oxidative coupling of benzene and ethylene (equation 189).464... 

Oxidative homocoupling of aromatic and heteroaromatic rings proceeds with Pd(OAc)2 in AcOH. Biphenyl (165) is prepared by the oxidative coupling of benzene [104,105], The reaction is accelerated by the addition of perchloric acid. Biphenyl-tetracarboxylic acid (169), used for polyimide synthesis, is produced from dimethyl phthalate (168) commercially [106], Intramolecular coupling of the indole rings 170 is useful for the synthesis of staurosporine aglycone 171 [107]. 

The oxidation of substituted aromatic amines with silver(l) carbonate on Celite has been shown to yield symmetrically substituted phenazines, albeit in poor yields. 2,7-Dimethoxy-hexafluorophenazine has been obtained upon electrolysis of solutions of 4-methoxytetrafluoro-aniline, and oxidative coupling of benzene-1,4-diamine with aniline or substituted anilines also gives phenazine derivatives. ... 

Recently, Yamaji and coworkers reported that the Pd(OAc)2-catalyzed oxidative coupling of benzene in the presence of 02 and acetic acid gave high selectivity of biphenyl (88%) when Mo02(acac)2 was used as a cocatalyst, but the turnover number remained low (up to 10) (Eq. 1, Scheme 6) [46]. 

Sasson and coworkers reported that the oxidative coupling of benzene in the presence of catalytic amount of PdCl2 (7 mol%) together with Zr(IV), Mn(II), and Co(II) acetates led to biphenyl in 89% yield in HOAc/NaOAc under air (10 atm). The combination of several oxygen-binding catalysts such as Zr(IV), Mn(II), and Co(II) acetates increased the concentration of oxygen in solution and therefore... 

Since the intermolecular oxidative coupling of benzene to biphenyl using stoichiometric amounts of PdCl2 was first described by van Helden and Verberg in 1965 [41], the intramolecular oxidative coupling of two arenes mediated by a palladium catalyst to synthesize cyclic compounds has also attracted great attention. 

The kinetics of the oxidative coupling of benzene under the action of the system PdCl2-NaOAc in acetic acid follows the equation ... 

Pd(II) can be expressed by the following general schemes. As a whole, two hydrogens are abstracted from two substrates A-H and B-H, generating Pd(0) and the product A-B. This reaction is stoichiometric with Pd(II), but the reaction becomes catalytic when Pd(0) is oxidized in situ to Pd(II) with appropriate oxidants (OX), and the whole reaction can be summarized by a third equation. For example, formation of vinyl acetate from ethylene and oxidative coupling of benzene can be understood formally as dehydrogenation reactions. These oxidative reactions using Pd(ll) are considered in Chapter 2. 

Recently, a major advance in the development of the reoxidation step was achieved through the use of heteropoly acids. Ishii and coworkers [12] found that the oxidative coupling of benzenes with electron-deficient alkenes can be performed at ambient pressure under oxygen and even under an air atmosphere when using molybdovanadophosphoric... 

Oxidative coupling of benzene proceeds using a Lewis-acid catalyst and an oxidant (the Kovacic method).For example, benzene is converted into PPP by treatment with CUCI2 and AICI3, as shown in Scheme 4.2. 

The oxidative coupling of benzene with styrene and some paraderivatives catalyzed by palladium (II) acetate was also investigated in the presence of MIP-CD [41]. Under this condition, the approach of the reacting molecules was also required for a sufficient reaction rate, and the product itself could be a model of the transition state. Trans-stilbene was used as a template for molecular imprinting. Pd-complexes with the synthesized macroligands turned out to be effective catalysts for the oxidative coupling process (Fig. 2.13). 

A new catalyst system composed of Pd(OAc)2 and dialkyl sulfide was reported recently as an effective system for the oxidative coupling of benzene. Also, the... 

The direct preparation of styrene from the oxidative arylation of ethylene constitutes a highly desirable reaction, notably from an industrial point of view. In 2000, Matsumoto and Yoshida reported a rhodium-catalyzed oxidative coupling of benzene and ethylene under ojgrgen. Rhodium(i) complexes such as Rh(acac)(CO)2, Rh(acac)(C2H4)2, [Rh(cod)Cl]2, and Wilkinson s catalyst [RhCl(PPh3)3] afforded similar catalytic activities in the presence of acetylacetone (acacH) and 0)g gen pressure, while a decreased rate was observed with Rh(iii) pre-catalysts and no reaction in the absence of acacH (Scheme 9.2). Additionally, the C-H bond activation was demonstrated to be the rate-limiting step. ... 

---