Hydrogenated fused polycycles

As already apparent from its name, this nomenclature type is based on the addition of atoms or groups of atoms to a parent structure and is restricted to very few special cases. The most important and at any rate indispensable application of this method is found in the naming of hydrogenated fused polycycles where hydrogenation is indicated by appropriate prefixes. 

Catalytic hydrogenation of polycyclic fused nitroso acetals is a more complex reaction sequence. This process was successfully used in the synthesis of natural and biologically active compounds (see, e g., Refs. 148, 367 and the review 99). 

The names of ortho-fused or ortho- and peri-fused polycyclic hydrocarbons with less than maximum number of non-cumulative double bonds are formed from a prefix dihydro- , tetrahydro- , etc., followed by the name of the corresponding unreduced hydrocarbon. The prefix perhydro- signifies full hydrogenation. When there is a choice... 

Univalent radicals derived from ortho-fused or ortho- and peri-fused polycyclic hydrocarbons with names ending in -ene by removal of a hydrogen atom from an aromatic or alicyclic ring are named in principle by changing the ending -ene of the names of the hydrocarbons to -enyl . 

Bivalent radicals derived from o/7/io-fused or ortho- and pen-fused polycyclic hydrocarbons by removal of a hydrogen atom from each of two different carbon atoms of the ring are named by changing the ending -yl of the univalent radical name to -ylene or -diyl . Multivalent radicals, similarly derived, are named by adding -triyl , -tetrayl , etc., to the name of the ring system. 

The initial rate of hydrogenation of fused polycyclic aromatics increases with the number of rings present phenanthrene > naphthalene > benzene. Only one ring is generally saturated at a time. This partial hydrogenation is accomplished because... 

Much research effort has been devoted to the study of tandem hetero-IMDA-cycloelimination reactions for the synthesis of fused polycyclic aromatic heterocycles. Nitrobenzene was found to be the best solvent for the tandem IMDA reaction/cycloelimination of hydrogen cyanide from 2- 2-[(trimethylsilyl)ethynyl]phenoxy -l,3-diazine (X = O)71,72. 

The initial rate of hydrogenation of fused polycyclic aromatics increases with the number of rings present ... 

Raney nickel and platinum, palladium, and rhodium catalysts have been used to accomplish the hydrogenation of polycyclic aromatics. Hydrogenation of fused polycyclic arenes leads to the cis- or fran -substituted cyclohexane derivatives. The cis product is usually obtained again this can be understood in terms of the mechanism proposed for aromatic hydrogenation (vide supra). 

A final example of induced mesogenicity in a multicomponent system is the well studied, but less well understood, carbonaceous mesophases which are comprised of a myriad of unidentified molecules which are created in situ as petroleum pitches are heated to temperatures where chemical transformations occur [163]. The processes leading to a mesophase involve decreases in both the elemental weight fraction of hydrogen and the group fraction of aliphatic carbon atoms [164]. Model studies have demonstrated that the component molecules of these phases are fused, polycyclic aromatic molecules with disk-like shapes the exact structures of the components depend upon the natures of the precursor molecules which are heated [164-167]. All of the carbonaceous mesophases somewhat resemble discotic nematic phases [168]. At least some of them probably represent another example of liquid crystallinity induced by mixing molecular components which, when separated, are not mesogenic. 

Robin D et al (1990) The electrocatalytic hydrogenation of fused polycyclic aromatic compounds at Raney nickel electrodes the influence of catalyst activation and electrolysis conditions. Can J Chem 68 1218-1227 (and refertaices in the Introduction)... 

Mann and coworkers have developed a four-component reaction using molecular hydrogen, carbon monoxide, an unsaturated carboxylic acid analogue 180, and a bisnucleophile 181 to create A-fused polycycles 182 in good to excellent... 

Oxidative annulations reaction of alkynes is one of the important methods to synthesize fused polycyclic heteroarenes [169-173]. Whereas the above examples show easy ruthenium catalysed insertions of alkynes into aromatic sp C-H bonds efforts have been made with related catalysts to perform the double insertion of alkynes into C-H and heteroatom-hydrogen bonds as a route to a variety of heterocycles. Chae S. Yi, has first shown, using ruthenium(ll) catalyst precursors [RuH(CO)(PCy3)2(NCMe)2]BF4 and preferably Ru3(CO)i2/NH4PF6, the alkenylation and double insertions of alkynes into C-H and N-H bonds for the transformation of indolines with terminal alkynes into quinoline derivatives [(Eq. 86)] [174, 175]. 

Nitro-polycyclic aromatic hydrocarbons, referred to as nitro-aromatic compounds hereafter, constitute one of the most troubling classes of environmental pollutants. They are derivatives of polycyclic aromatic hydrocarbons (PAHs) that contain two or more fused aromatic rings made of carbon and hydrogen atoms and at least one nitro group (Fig. 10.1). Concern about these compounds arises partly from their ubiquity nitro-aromatic compounds are released to the environment directly from a variety of incomplete combustion processes [1] and are also formed in situ by atmospheric reactions of PAHs [2]. Nitro-aromatic compounds have been found in grilled food in diesel, gasoline, and wood-smoke emissions and are commonly found in atmospheric particulate matter, natural waters, and sediment [3-8],... 

Apart from the construction of phenanthrenes, carbene complexes have also been used for the synthesis of more extended polycyclic arenes. An unusual dimerization of chromium coordinated ortbo-ethynyl aryl carbenes results in the formation of chrysenes (Scheme 37) [81]. This unusual reaction course is presumably due to the rigid C2 bridge that links the carbene and alkyne moieties, and thus prevents a subsequent intramolecular alkyne insertion into the metal-carbene bond. Instead, a double intermolecular alkyne insertion favored by the weak chromium-alkyne bond is believed to occur forming a central ten-membered ring that may then rearrange to the fused arene system. For example, under typical benzannulation conditions, carbene complex 97 affords an equimolar mixture of chrysene 98a and its monochromium complex 98b. The peri-interactions between the former alkyne substituent (in the 5- and 11-positions) and the aryl hydrogen induce helicity in the chrysene skeleton. 

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