Naphthacene, synthesis

The synthesis of a tetraphenyl derivative (rubrene, Expt 6.13) of the linearly fused tetracyclic aromatic hydrocarbon naphthacene involves an interesting intermolecular cyclisation process between two molecules of 1-chloro-1,3,3-triphenylpropa-1,2-diene. This substituted allene is formed in situ from 1,1,3-triphenylprop-2-yn-l-ol (Expt 5.41) when the latter is allowed to react with thionyl chloride and the resulting chlorosulphite ester heated with a little quinoline cyclisation occurs spontaneously under these reaction conditions to give rubrene which has an intense red colour. 

H. C. Synthesis of animated naphthacene-triones precursors to aminated anthracy-dines. Synth. Commun. 1993, 23, 3223—3229. 

The basic methods for the synthesis of 5,12-naphthacenequinone are reactions involving the oxidation of naphthacene and its derivatives as well as cyclization reactions, with reactions of intramolecular acylation and diene synthesis being of particular interest.7... 

One final interesting application of CAN which exemplifies one of the many possible reactions of qui-nones comes from Hassall and coworkers in their synthesis of 4-demethoxydaunomycinone (47). Thus, oxidation of the boronate (42) with CAN gave the crude quinone (43) which was reacted with trans-1,2-bis(acetoxy)-l,2-dihydrobenzocyclobutene (44) to give the tetracyclic quinone (45) in an impressive 79% overtdl yield. Deacetalization and reductive acetylation to the naphthacene (46), followed by oxidation with anhydrous chromium trioxide and deprotection with boron trichloride afforded the target compound (47 Scheme 10). 

In going from benzene to pentacene the largest sum of the free valence of a pair of atoms in a para position increases as does the ease of the diene synthesis in this series. It is well known that maleic anhydride hardly reacts with benzene or naphthalene. A reaction takes place with anthracene and even more readily with naphthacene and pentacene.12... 

Pentacene. Benzo[i>]naphthacene 2,3,6,7-diben-zoanthracene iin-naphthoanthracene, CnHM mot wt 278,35. C 94.93% H 5,07%. Synthesis from m-xylene or from 4-benzyl-1,3-dimethylbenzene and benzoyl chloride in presence of aluminum chloride or from terephthalyl chloride and o-tolylmagaesium bromide Oar, John, Ber, 62, 940 (1929) 63, 2967 (1930) 64, 981 (1931). Synthesis by reduction of 6,13-pentacenequinone Bruckner etal. Tetrahedron Letters 1960, no. 1,5 Bruckner, Tomas z. Acta Chim. Acad. Sci Hung. 28(4), 405 (196l). Structure Campbell et al, Acta Cryst. 14, 705 (1961). 

Synthesis. The ketones used in the syntheses were 1-phenalenone (Aldrich), 7H-benz[de]anthracen-7-one (Phaltz and Bauer), 6H-benzo[de]pyren-6-one (W. Schmidt, Biochemical Institute for Environmental Carcinogens, Ahrensburg, West Germany), and 6H-benzo[/g]naphthacen-6-one (W. Schmidt). The ketone structures are shown in Chart I. 

Scheme 9 Synthesis of enantiomerically pure naphthacene derivatives...

Synthesis gas (1 1 GO) added to a soln. of naphthacene and dicobalt octa-... 

Moreover, they are versatile building blocks for the synthesis of functionalized naphthalenes, anthracenes, and naphthacene natural products [8]. Recently, Rh-catalyzed C-H activation followed by nucleophilic addition to aldehydes emerged as a powerful alternative to access phthalides. In 2012, Li and coworkers developed a novel Rh(III)-catalyzed synthesis of three substituted phthalides from benzoic acids and aldehydes through carboxylate-directed ortho-C-H functionalization and subsequent intramolecular cyclization (Scheme 6.2a) [9]. In 2013, GooCen and coworkers described the straightforward synthesis of S-alkylidenephthalides from benzoic acids and aliphatic acids or anhydrides in the presence of [Rh(cod)Cl]2 and CsF (Scheme 6.2b) [10]. 

Dufraisse, C. and Horclois, R., Synthesis of naphthacenes with the characteristics of rubrenes. Bull. 

Benzyl- and allyltins present a much lower reactivity in Stille coupling than orga-notins containing a Sn-Csp bond. Allyltins have not been frequently used, due in part to the tendency of products to reconjugate after the cross-coupling when ole-finic or aromatic substrates are used as electrophilic partners [38], and the frequent loss of regioselectivity observed whith y-substituted allyltins [39]. A nice application is represented by the reaction of a /3,y-disubstituted allyltin with a naphthoquinone-bromide used in a biomimetic-type synthesis of benzo [a]naphthacene quinines related to Pradimicinone [40] (Scheme 6). 

---