Arenes hydrogenation, partial

Finally, the development of modified nanoparticles with a better hfetime and activities for various applications in catalysis remains an important challenge. Several recent investigations have made possible interesting results in various research areas around soluble nanoparticles synthesis, characterizations and their applications. In this context, total, partial or selective arene hydrogenations have received considerable attention and could still be... 

In summary, partial hydrogenation of anisole to 1-methylcyclohexene by polyoxoanion-stabilized Rh(0) nanoclusters is very modest but could in the future be an interesting additive study in the monocyclic arene hydrogenation research area. 

The partial arene derivative hydrogenation into cyclohexene or cyclohexa-diene as intermediates is also investigated. The process developed by Asahi Chemical Industry in Japan is an example of the selective formation of cyclohexene [6]. In the future, this reaction could be an active area of research due to the potential of the intermediate in organic synthesis. 

As judiciously reported by the authors, the yields are too low for technical appUcations but this reaction represents the second example of partial hydrogenation of monocyclic arene by soluble transition metal nanoparticles. 

Accordingly, hydrogenation of p-xylene yields a 1 3 mixture of cis- and trans-1,4-dimethylcyclohexane. Both observations suggest that dissociation and readsorption of the partially reduced arene take place. 

Steric arguments suggest that the addition of dihydrogen to [Os]-arenes should occur on the arene face opposite that of metal coordination. This theory is supported by the generation of l-d4 upon the partial deuteration of 1. Furthermore, the hydrogenation of complexed anisole (5) under anhydrous conditions yields complexed 3-methoxycyclohexene (6), in which the methoxy group is syn to the metal. It was found, however, a trace of water in the reaction mixture results in the formation of complexed cydohexenone (7), presumably from the attack of water on the dihydroanisole intermediate [13]. 

The possible number of inherently chiral structures and conformers further increases if the calixarene contains both different phenolic units and different bridges in the macrocyclic skeleton. For example, two chiral monoethers 88a,b are available from dihomooxacalix[4]arenes (one -CH2-0-CH2- bridge instead of -CH2-).17188b is the preferred product of the mono-O-alkylation, since the negative charge of the respective phenoxide anion is better stabilized by intramolecular hydrogen bonds due to the smaller distance between the phenoxide anion and the hydroxy groups. Tetraketone derivatives (Y = CH,-C(0)-R) in the two possible partial cone conformations, have been prepared in moderate yields. 

On the other hand, no indication of a directionality of hydrogen bonds234 could be observed for the C4-symmetrical calix[4]arenes 97 with m-methyl groups (or their partial ether derivatives) where such a directionality should lead to two diastereomeric species.235... 

With nickel(II) 2-ethylhexanoate and triethylaluminum, tetralin (59) is obtained by hydrogenation of naphthalene (55). Polycyclic aromatics, such as anthracene (57 equation 8), 9-methylanthracene and 9-trifluoroacetylanthracene, are partially hydrogenated to 1,2,3,4-tetrahydroanthracene derivatives by use of [Rh(DPPE)(arene)]+ in methanol and by ruthenium hydride complexes having triphenylphosphine ligands... 

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