Coronene synthesis

Therefore, photoreactions via pentahelicenic intermediates may lead to undesired products. In the synthesis of a 3,15-disubstituted heptahelicene (20) starting from a (3 + 1 + 1) derivative (19) the coronene derivative (21) was formed as a side product20). 

Corannulene, C2oH10, dibenzo y/ /, mno] fluoranthene, shown in Fig. 1(a), is a bowl-shaped PAH with 5-fold symmetry [6], and has a one-third skeleton of C60 (see Figs 1(c) and (d)). Recently, convenient synthesis for corannulene [7,8] has been developed. On the other hand, coronene, C24H12, hexabenzobenzene, shown in Fig. 1(b), has a flat structure with a 6-fold symmetry axis. 

Figure 4.6 Structure of oligothia-dendrimers used for the controlled formation of AuNPs,161 and of 1,2,3,4,5,6,7,8,9,10,11,12-dodecakis-p-tolylsulfanyl-coronene used for the synthesis of 1.0 nm AuNPs.162...

If such oxidative couplings occur vithin the same molecule, cycliza-tions, usually to six-membered rings, take place. Anhydrous aluminum chloride proves useful in such intramolecular dehydrogenations. At 120 °C, it cyclizes benzil to 9,10-phenanthrenequinone [407] and bridges benzene rings in the synthesis of coronene [408], At the same time, partial aromatization takes place (equations 46 and 47). 

Cyelodehydration. The first recorded use of the reagent provides a dramatic comparison in potency of PPA with three other reagents. In the synthesis of dibenz-coronene and coronene, Scholl and Meyer effected the first of four ring closures of the hexacarboxylic acid (I) with concentrated sulfuric acid at room temperature. The red-violet product (2) was obtained in analytically pure form by precipitation from a solution in ammonia. C ycli/.alion to (.1) was accomplished with 20% oleum at 100° the product was isolated us the violet-black sodium salt by adding sodium... 

Cyclodehydrogenation of heterohelicenes. Several syntheses of coronene and related polynuclear hydrocarbons involve cyclodehydrogenation with aluminum chloride or sodium aluminum chloride to form aryl—aryl bonds (Scholl reaction). In their studies on the synthesis of heterohelicenes, Wynberg and... 

Retention behavior was compared with a series of planar PAHs pyrene, benzo[ghi]perylene, coronene, benzo[pqr]naphtho[8,l,2-hcd]perylene, naph-tho[8,l,2-ahc]coronene, and ovalene (obtained from Aldrich or by synthesis). 

Scheme 13.26 Photoqfclization of [2.2.2]paraqfclophanes 96 in the synthesis of coronene derivatives 97.

Strategies in Organic Synthesis for Condensed Arenes, Coronene, and Graphene... 

The Diels-Alder reaction represents one of the most efficient methods for assembling six-membered carbon cycles. As this structural element is the characteristic of graphene-type structures, Diels-Alder reactions have been applied successfully for the synthesis of PAHs such as acene and coronene. 

Coronene 16 can be viewed as a superbenzene. The series was continued with the synthesis of supemaphthalene 53 and supertriphenylene 56, using different phenylacetylenes and tetraphenyl substituted cyclopentadienone. Two selected examples 53 and 56 are shown in Scheme 15 [39,40]. 

Additionally, a mechanism via a metal-carbene intermediate has been observed. In the example shown in Scheme 36 a Ru catalyst was used to form four C-C bonds in one step for the synthesis of coronene 16 (Scheme 36) [92]. 

Scheme 36 Synthesis of coronene via four-fold Ru-catalyzed cyclization [19]...

Shen H-C, Tang J-M, Chang H-K et al (2005) Short and efficient synthesis of coronene doivatives via ruthenium-catalyzed benzannulation protocol. J Org Chem 70 10113-10116. doi 10.1021/jo0512599... 

Kiibel C, Eckhardt K, Enkehnann V, Wegner G, Mullen K (2000) Synthesis and crystal packing of large polycyclic aromatic hydrocarbons hexabenzo[bc, ef, hi, kl, no, qr]coronene and dibenzo[fg, ij]phenanthro[9,10,l,2,3-pqrst]pentaphene. J Mater Chem 10 879-886... 

The heterohelicenes can be used for the synthesis of a new class of polycyclic aromatic compounds, similar to coronene or corannulene, for which Wynberg suggests the name heterocirculenes. Thus the hetero-hexahelicene (446) gives (453) in 95% yield upon heating for several minutes at 140 ° with an AlCls-NaCl melt, and upon reaction with maleic anhydride and chloranil (453) yields (454). Decarboxylation of the latter or the corresponding acid with copper powder in quinoline furnishes the hetero-circulene (455). ... 

A new type of a substituted thiophene represents bis(thienyl) coronene, leading to an alternating polymer with bis-thiophene and coronene units [76]. Synthesis and properties of processable poly(thiophene) are described in [77]. 

A radialene-type core also appears in the appropriate bond resonance structures of the so-called [ ]circulenes, where the central -sided ring is surrounded by n fused benzenoid rings (Figure 4.4) [107]. As the first members of the homologous series, the parent structures comprise the [3]circulene (probably too strained to be accessible by synthesis), the so far unknown [4]circulene (153), [5]circulene or corannulene (154) which is a substructure of buckminsterfullerene (Cgg), the long-known [6]circulene or coronene (155), and [7]circulene (156). 

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