Eight cobalt catalysts

A [2 + 2 + 2]-cycloaddition reaction is also known, facilitated by Ni(cod)2 or a cobalt catalyst. " " [2 + 2 + 1]-Cycloaddition is known.A cobalt catalyst is used for a [4- -2- -2]-cycloaddition of 1,3-butadiene and bicyclo[2.2.2]octa-2,5-diene. " " " Eight-membered rings are products by a rhodium catalyzed [4- -2- -2]-cycloaddition. " " Chromium catalysts are available for [6-1-4]-cycloadditions... 

Later, Chung et al. successfully developed an intramolecular Pauson-Khand reaction in water without any cosolvent by using aqueous colloidal cobalt nanoparticles as catalysts. The catalyst was prepared by reducing an aqueous solution of cobalt acetate containing sodium dode-cyl sulfate (SDS) surfactant. The cobalt nanoparticle could be reused eight times without any loss of catalytic activity (Eq. 4.57).107... 

In the presence of nickel(0), tethered diene-VCPs react to produce eight- and five-membered ring products (Scheme 2). Palladium(O) and cobalt(m) were also tried but produced only decomposition products. However, in the presence of Wilkinson s catalyst (RhCl(PPh3)3), tethered diene-VCP 1 was cleanly converted to triene 4 in 91% yield. Although the desired cycloaddition reaction was not obtained, the cleavage of the cyclopropane ring was encouraging.22... 

Vicinal diols are also oxidized to carboxylic acids. 1,2-Dihydroxydec-ane in benzonitrile shaken with oxygen at atmospheric pressure at 100 °C in the presence of cobalt laurate as a catalyst furnishes, after 2 h, a 66% yield of pelargonic (nonanoic) acid [69]. Electrolysis at 20-30 °C in aqueous potassium carbonate with nickel electrodes in an undivided cell and a current of 0.3 A yields 74-84% of dicarboxylic acids from both cis and trans cyclic diols having six to eight carbons in the rings (equation 307) [122]. 

Cordierite monoliths were coated with an alumina washcoat and stabilised at 550°C. Some of the samples were then immersed in either an aqueous solution of cerous or cobalt nitrate, dried and calcined in air at 550°C at which the metal nitrates decomposed into their oxides [11]. The samples were weighed and the procedure was repeated until 40 mg of the metal oxide had been deposited onto the alumina washcoated monolith samples. Pt and Pd were applied by direct impregnation using aqueous solutions of HaPtCla and PdCb followed by diying and calcination in air at 550°C [8]. The Pt and Pd loadings (2.0 and 1.09 mg, respectively) of the catalysts were equal on molar basis. The nominal composition of the eight catalysts prepared are listed in Table 1. 

Takahashi et al. reported that acetylenes could be transformed into indan-l-ones under water gas shift condition with cobalt as the catalyst in 1990 [6]. Nevertheless, the reaction proceeded at harsh conditions (100 atm of CO and 220 °C), and eight examples were provided in moderate to good yields (Table 15.1). 

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