Fused Polycyclic Compounds

Fused-ring compounds have a pair or pairs of adjacent carbon atoms common to two rings. Over 35 carbocyclic examples have trivial names, some of which need to be memorized as building blocks for names of more complex examples. The names end with ene, indicating a maximum 

TABLE 1.1 Trivial Names of Some Fused Polycyclic Hydrocarbons 

Fusing more rings onto one of these basic systems may give another one with a trivial name. If not, a name including the two rings or ring systems with bracketed locants is used, as in the following example. 

Since a side of the anthracene is shared, the sides are labeled a, b, c, and so on, where carbons numbered 1 and 2 constitute side a and 2 and 3 constitute side b, continuing in order for all sides. The earliest letter of the anthracene is used to indicate the side fused, and the ring fused to it appears first. The o ending of benzo is deleted here because it would be followed by a vowel. 

First letter the sides of azulene. The benzo ring is fused to both the c and d faces as indicated in the brackets. Now reorient the system for numbering. The choice of which two rings go on the horizontal axis and 

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The application of this procedure to the fused polycyclic compound E, which already has a linear dual and only the last two steps (iii-iv) apply to it, leads to a linear acyclic structure F which may be traced back to the biogenetic cyclisation of squalene to lanosterol via cationic intermediates, as well as to the stereospecific cationic cyclisation of polyolefins studied by Johnson [18]. 

Caryophyllenes, as an example of two naturally occurring isomeric sesquiterpenes containing a medium-sized ring, in which the success of the total syntheses lies in the stereoselective control of a chiral centre, in a common synthetic key intermediate, which governs the configuration (JE or Z) of the double bonds present in each one of the two isomers. In this context, a brief reference to Cecropia Juvenile Hormone synthesis by the Syntex group, as well as to Johnson s cationic cyclisation of unsaturated polyolefins to fused polycyclic compounds, is made. 

Fused polycyclic compound 1151, that may serve as an intermediate in the synthesis of Ergot alkaloids, was obtained by submitting indole 1150 to the PKR under the usual conditions (Equation 264) <2004JOC5413>. The results showed the formation of compound 1151 in good yield (60%) using method B and in moderate yield (37%) using catalytic conditions E. 

Hiickel s rule has been expanded to cover fused polycyclic compounds because when these compounds have the requisite number of electrons, they also show unusual stability. 

Terzidis MA, Tsoleridis CA et al (2008) Synthesis of chromeno[2,3-b]carbazole and chro-meno[3,2-f]indazole derivatives. A new class of indole- and pyrazole-fused polycyclic compounds using o-quinodimethane chemistry. A reactivity and regioselectivity computational study. ARKIVOC 132-157... 

Rapid Access to 3-(Aminomethyl)isoquinoline-Fused Polycyclic Compounds by Copper-Catalyzed Four-Component Coupling, Cascade Cyclization, and Oxidation Yusuke Ohta, Yushi Kubota, Tsuyoshi Watabe, Hiroaki Chiba, Shinya Oishi, Nobutaka Fujii and Hiroaki Ohno J. Org. Chem. 2009, 74, 6299-6302. Reproduced with permission... 

Rapid Access to 3-(Aminomethyl)isoquinoline-Fused Polycyclic Compounds by Copper-Catalyzed Four Component Coupling, Cascade Cyclization, and Oxidation... 

In conclusion, the author has developed a novel route to isoquinoline-fused polycyclic compounds by a four-component coupling and cascade cyclization strategy. In this reaction, the cyclization/oxidation step can be accelerated by use of an oxygen atmosphere, giving rise to improved yields of the cyclized products in many cases. Because this four-component reaction catalytically forms one carbon-carbon and four carbon-nitrogen bonds producing only H2O and H2 as the... 

Table 4 Synthesis of (Aminomethyl)isoquinoline-fused polycyclic compounds...

General Procedure for Synthesis of (Aminomethyl)isoquino-line-Fused Polycyclic Compounds by Domino Mannich-Type Reaction and Cascade Cyclization Synthesis o/6-/(N,N-Diisopropylamino)methyl]-3,4-dihydro-2H-pyrimido[2,l-SL] isoquinoline (12a) (Table 1, Entry 10)... 

In relation to the three-component indole formation, a novel four-component synthesis of 3-(aminomethyl)isoquinoline was developed. The reaction of 2-ethynylbenzaldehyde with (HCHO) , secondary amine, and t-BuNH2 proceeds through Mannich-type reaction, cycUzation, and elimination of t-butyl group. By the use of alkane diamine instead of r-BuNH2, 3-(aminomethyl)isoquino-line-fused polycyclic compounds were also synthesized by cascade cycUzation and oxidation. Changing the carbon tether of the diamine component led to the synthesis of isoquinoUnes fused with various heterocycles. 

Nishibayashi, Y, Yoshikawa, M., Inada, Y., Hidai, M., Uemura, S. (2004). Ruthenium-and platinum-catalyzed sequential reactions selective synthesis of fused polycyclic compounds frompropargylic alcohols and alkenes. Journal of the American Chemical Society, 126,16066-16072. 

Photocycloadditions are also exploited in the synthesis of fused polycyclic compounds. Tetracyclic (4-hetera)cyclopent[, c]acenaphthylenes can be synthesized by light-induced cycloaddition of 4-alk-l-ynylcoumarins to 2,3-dimethylbut-2-enes (Scheme 6.33). Addition of triplet-excited 4-alk-l-ynylcoumarin to the alkene affords the triplet biradical, which undergoes 1,5-cyclization to cyclopentenylcar-bene. The latter undergoes electrocyclic ring closure and [1,9]-H shift to yield the product [37]. 

Helicenes Helicenes are fascinating molecules displaying a broad range of properties. The cobalt-catalyzed [2 + 2 - - 2] cycloaddition allows the construction of such angularly fused polycyclic compounds [68]. Stara et al. reported various applications, using CpCo(CO)2 or CpCo(C2H4)2 as a catalyst, like the one depicted in Scheme 1.35 [68b]. This topic is covered in detail in Chapter 10. 

Cataiytic transformation has also been accomplished. Kawaguchi et al. reported the palladium-catalyzed intramolecular 0-arylation of 2-[2-(pseudo)haloaryl]phenols [14]. 2-(2-Chlorophenyl)phenol (68) was converted to dibenzofuran (69) successfully in the presence of palladium(II) acetate/phosphine ligand, but the authors did not explore the scope of this reaction (Scheme 23.26). In addition, they accomplished the synthesis of fused polycyclic compounds such as dibenzo[(i,fi ]benzo[l,2-fe 4,5-fc jdifurans 70 [14] and oxa[7]helicene 71 [17] using this methodology (Scheme... 

In 2001, Mauleon et al. reported an unusual palladium-cascade arylation of a,P-unsaturated phenyl sulfones 23 under Heck reaction conditions [12]. Contrary to the work of Fuchs and others [13], Mauledn et al. described the intermolecular reaction of a,P-unsaturated sulfones with a large excess of iodobenzene (or / -substituted iodoarenes) in the presence of Ag COj as base, which occurred mainly through a complex cascade reaction in which three molecules of iodobenzene and one molecule of vinyl sulfone were involved, forming fused polycyclic compounds 25 rather than the Heck trisubstituted olefin expected. The authors propose a mechanism involving Heck reaction and C-H activation pathways (Scheme 6.5). 

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