Polycyclic heteroarenes

Polycyclic Arenes and Heteroarenes Synthesis, Properties, and Applications, First Edition. Edited by Qian Miao. 2016 Wiley-VCH Verlag GmbH Co. KGaA. Published 2016 by Wiley-VCH Verlag GmbH Co. KGaA. 

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Under different conditions [PdfOAcj2, K2CO3, flu4NBr, NMP], the 1 3 coupling product 86 with 4-aryl-9,10-dihydrophenanthrene units was obtained. The product 86 was transformed into a variety of polycyclic aromatic compounds such as 87 and 88[83], The polycyclic heteroarene-annulated cyclopen-tadicnc 90 is prepared by the coupling of 3-iodopyridine and dicyclopentadiene (89), followed by retro-Diels Alder reaction on thermolysis[84]. 

S-Containing Polycyclic Heteroarenes Thiophene-Fused and Thiadiazole-Fused Arenes as Organic Semiconductors... 

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]. 

Under similar reaction conditions, a regioselective oxidative annulation of quinazolones with alkynes was reported by Peng and coworkers (Eq. (7.31)) [39]. A series of fused polycyclic heteroarenes were formed in moderate to high yields with a broad substrate scope. The substrates bearing electron-donating... 

On the way to further extension of the scope of Cp Co "-catalyzed C-H functionalization, Glorius and coworkers developed a condensation reaction of 2-arylpyridine derivatives and diazoesters to form unique polycyclic heteroaromatics having 6//-pyrido[2,l-a]isoquinolin-6-one skeletons (Scheme 10.15) [38]. The reaction is achieved by the combination of a bench-stable Co precatalyst [Cp Co(CO)l2] [39], a silver salt (AgSbFg), and an acetate source (KOAc) in trifluoroethanol. The in situ-formed Cp Co catalyst is proposed to play a dual role in this condensation reaction. First, it promotes formal carbene insertion into the ortho C-H bond through pyridine-directed C-H metalation, cobalt-carbene formation, carbene insertion into the aryl-Co bond, and protodemetalation. Second, it acts as a Lewis acid to facilitate nucleophilic attack of the pyridine moiety to the ester group, which eventually leads to the product through aromatization and elimination of methanol. The thus-synthesized polycyclic heteroarenes exhibit bright and color-tunable fluorescence in solution and in the solid state. 

Fig. 8.105 Examples of metal-catalyzed synthesis of phenanthrenes and polycyclic heteroarenes.

The intermolecular implementation of the above was reported by Tsuchimoto and Shirakawa et al [228]. In their work, 2-arylindoles were annulated with propargyl ethers with In(ONf)3 (ONf = nonaflate, C4F9SO3) as catalyst, resulting in a more convenient access to polycyclic heteroarenes (Figure 8.106). Bithiophenes and bifurans could also undergo the annulation reaction in an analogous fashion, albeit with lower yields. The structure of the major side product from the bithiophene... 

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