Monocycle arenes

The degradation of BTEX both individually or in admixture has been shown in a lignindegrading white-rot fungus under nonlignolytic conditions, and was confirmed with ring-labeled toluene (Yadav and Reddy 1993). Interest in fungal transformation of PAHs is noted in the next part of this chapter, and illustrative examples of the hydroxylation of monocyclic arenes include the following (Smith and Rosazza 1983) ... 

The total hydrogenation of benzene derivatives represents an important industrial catalytic transformation, in particular with the conversion of benzene into cyclohexane, a key intermediate in adipic acid synthesis, which is used in the production of Nylon-6,6 (Scheme 1). This reaction is still the most important industrial hydrogenation reaction of monocyclic arenes [1]. 

In the past five years, the use of nanoparticles in this active research area has received increased attention since some homogeneous catalysts have been shown to be nanoheterogeneous [24-26]. Today, soluble noble metal nanoparticles are considered as reference in monocyclic arene catalytic hydrogenation under mild conditions and several stabilized systems have been reported [27,28]. 

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. 

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. 

Scheme 9.9 Total hydrogenation of monocyclic arene compounds by various zerovalent noble-metal nanoparticles.

This section also includes nitrated monocyclic arenes with halogen atoms directly attached to the benzene ring. 

Monochromatic organic light-emitting diodes light-emitting electrochemical cells, 12, 175 with organometallic emitters, 12, 158 Monocyclic arenes, in Ru and Os compounds, 6, 466 Mono(cyclooctatetraenyl) actinide(IV) compounds, preparation, 4, 227... 

Two comprehensive reviews of arene oxides-oxepins have been produced to date. The first review in 1967 dealt mainly with the concept of valence tautomerism in the monocyclic arene oxide-oxepin series, while the second article in 1973 also included the arene oxides of polycyclic aromatic hydrocarbons (PAH) and placed more emphasis upon their chemistry and biochemistry. In addition, a number of more speciahzed reviews dealing with aspects of arene oxide-oxepin chemistry including oxepins and hydrooxepins, solution chemistry, and roles in metabolism have appeared. The profusion of papers associated with the title arene oxides-oxepins that have appeared since 1973 (> 300 papers) allied to the significance of advances contained therein has prompted the present chapter. Particular stress is placed upon the material appearing during the period 1973-1982, with appropriate cross-references to the earlier literature. ... 

Structural information in the crystalline state can be obtained directly by x-ray diffraction studies, but this method has not been used extensively in the arene oxide-oxepin series since the majority of the monocyclic arene oxide-oxepins synthesized to date have been liquids and since chemical instability at ambient temperature is a common feature of many mono- and polycyclic arene oxides. X-ray crystal structure analysis has been carried out on the relatively stable K-region arene oxides 2-4. ° Similarly, an x-ray analysis of 5, a crystalline annelated benzene oxide (which, however, exists in both arene oxide and oxepin form in solution), has been reported and indicates that the six-membered ring is almost planar. The oxepin ring in compound 6 has been shown to exist in the boat conformation both in solution and in the crystalline state. The structural information thus obtained in the crystalline state is totally consistent with the spectroscopic data and the chemical reactivity of the arene oxides in solution and has been used in theoretical studies of the arene oxide-oxepin system. ... 

Boyd, D.R., M.R.J. Dorrity, M.V. Hand, J.F. Malone, N.D. Sharma, H. Dalton, D.J. Gray, and G.N. Sheldrake. 1991. Enantiomeric excess and absolute configuration of ds-dihydrodiols from bacterial metabolism of monocyclic arenes.. Am. Chem. Soc. 113 666-667. 

Ushakova et al. (1979) examined the hydrocarbon content of egg yolk, finding 15 to 30 mg alkanes and cycloalkanes per kilogram egg yolk, 1 to 3 mg/kg n-alkanes, 15 to 17 mg/kg squalenes, and about 1 mg monocyclic arenes/kg egg yolk. Table 14.2 shows the FA composition of whole lipids and several fractions. 

Shindo K, Nakamura R, Osawa A, Kagami O, Kanoh K, Furukawa K, Misawa N (2005) Biocatalytic synthesis of monocyclic arene-dihydrodiols and -diols by Escherichia coli cells expressing hybrid toluene/biphenyl dioxygenase and dihydrodiol dehydrogenase genes. J Mol Catal B Enzym 35 134-141... 

A particularly active catalyst for the hydrogenation of polycylic arenes has been generated from the anionic hydridoruthenium precatalyst in Figure 15.18, discovered by Grey and Fez. This system catalyzes the hydrogenation of antliracene to 1,2,3,4-tetrahydroanthracene under relatively mild conditions with a turnover frequency of > 50 h" and a turnover number of > 100 (Equation 15.96). Both anthracene and naphthalene are partially hydrogenated in the presence of tlais catalyst, but monocyclic arenes do not react. 

Polycyclic aromatic compounds, such as naphthalene and anthracene, are weU known to participate in Diels-Alder and related transformations as these reactions typically result in loss of aromaticity in only one of several arene rings [38]. Such cycloadditions are rarely observed in simpler monocyclic arenes. Several examples of intramolecular [3+2] cycloaddition between an arene and an attached nitrile oxide moiety have been reported [39]. Additionally, 4+2 cycloadditions (also intramolecular) between phenyl groups and attached aUenes have been examined [40]. Allene substrates can be conveniently genwated by base-induced isomerization of alkynyl amides under conditions also suitable for cycloaddition, thweby affording a one-pot method to convert substrates such as 42 to tricyclic products 43 (Schane 15.16) [41]. Elaboration of 43 and structurally related... 

Rate constants for the acid-catalysed dehydration of different types of monocyclic arene hydrates have been determined by UV spectrophotometry. General acid catalysis was not observed, and linear plots of pseudo-first-order rate constants for dehydration against hydronium concentration were obtained. A Hammett plot of the second-order rate constants for acid-catalysed dehydration shows an excellent correlation with <7+ values and yields a large negative p-value of -6.5. The results are consistent with ratedetermining formation of a benzenium ion in which direct mesomeric interaction with the substituent occurs, presumably permitted by the coplanar arrangement of the diene and carbocation centre in the intermediate. 

The use of bisnaphthalene chromium and (naphthalene)Cr(CO complexes as reagents for further arene complexes has been examined. The (naphthalene)Cr(CO) substitutes 10 /10 times faster than monocyclic arenes. 

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