Heterocyclotetraaromaten waren bisher unbekannt. Es wurden 4 Vertreter (6a, 7,9,11) mit nucleophilen aromatischen Ringgliedern und 1 Vertreter (13b) mit elektrophilen aromatischen Ringgliedern dargestellt. Mit einer Ausnahme erfolgte die Cyclisierung der Vorstufen durch oxidative Kupplung. Heterocyclopolyarornatics, VI ' ) Heterocycfotetraarornatics Containing Similar Kinds of NucleiHeterocyclotetraaromatics have been unknown hitherto. Now were prepared 4 representatives (6a, 7,9, 11) with nucleophilic and 1 representative (13b) with electrophilic aromatic ring members. With one exception the cyclisation of the precursors occurred by oxidative coupling.1943 stellten Rapson, Shuttleworth und vaii Niekerk *) wie angegeben das Tetraphenylen 2a und damit den ersten Cyclotetraaromaten dar. Analoge Synthesen, die von der zu 1 analogen Dilithium-Verbindung ausgingen, beschrieben Wittig und Mitarbb. 3 , 4 ) . Als Intermediarprodukte wurden dabei at-Komplexe nachgewiesen. ___, 1 1. Synthesen 2n 2b Die bei der Darstellung von 2a und hoheren Homologen3) bewahrte Methode der oxidativen Kupplung mit Ubergangsmetallhalogeniden konnte, wie aus dem Formelschema l ) V. Mitteil.: T h . Kauffmann, D. Tigler und A . Wolterrnann, Tetrahedron Lett. 1977, 741. Bei den Formelbildern wurde wegen der besseren Obersichtlichkeit darauf verzichtet, die Mengen des eingesetzten Lithiierungsmittels und Obergangsmetallhalogenids (siehe experimenteller Teil) anzugeben. Die Ausbeuteangaben sind auf ganze Zahlen ab-oder aufgerundet. 9, L.
2,T-Bipyridyl konnte erstmals nucleophil alkyliert werden. Bei der Umsetzung mit Methyl-und n-Butyllithium entstand je nach den Bedingungen sehr selektiv die 6-Alkyl-oder 6,6-Dialkyl-Verbindung (41 -64 %). Die Anwendung relativ tiefer Temperaturen erlaubte in mittlerer Ausbeute auch die Darstellung von CAryl-Verbindungen (Aryl = Phenyl, 2-Pyridyl). Im Konkurrenzversuch zeigte 2,T-Bipyridyl gegeniiber n-Butyllithium deutlich hohere elektrophile Aktivitat als Pyridin. Protophanes and Polyaromatics, XXII"Nucleophilic Alkylation and Arylation of 2,2'-Bipyridyl 2,Z'-Bipyridyl was alkylated by nucleophilic substitution for the first time. The reaction with methylor n-butyllithium yielded very selectively either the 6-alkyl-or the 6,6'-dialkyl compound (41 -64 %) depending on the conditions. Applying relatively low temperatures it was possible to prepare 6-aryl-2,2-bipyridyIs (aryl = phenyl, 2-pyridyl) in medium yields. In a competition experiment with n-butyllithium 2,2'-bipyridyl was significantly more electrophilic than pyridine.Ziegler und Zeiser 1 ') XXI.
are well-known compounds141, the thiooxoketones (9) and dithiones (10) are new compounds. Their structures have been determined by high resolution NMR and mass spectrometry; an X-ray structure of (9a) confirmed the assignments.The first step of the synthesis-the formation of the cyclic diureas (4) or (5)-is supported by the hydrolysis of (4) to (11) in quantitative yields. The second step-the unsymmetric transannular ring closure (see Scheme 1)-might well beaccelerated by the concurrent regeneration of the isocyanate or isothiocyanate group and release of the imidazole moie-tY.The above mentioned successive application of two reagents permits the synthesis of the unsymmetric product (9) in two ways: from (1) with (2) and (7) via (4) or with (3) and (6) via (5). Moreover, this approach replaces composite reagents (carbonyl i~ocyanates~~] or isothiocyanatesI6]) by simple ones 1(4, (3), (6), ( 7~. ExperimentalA 0.5 M solution of (la) in benzene is gradually mixed at room temperature with a 0.5 M solution of (3) in benzene (using a Sage syringe pump; Orion, Research Inc.). The resulting crystalline precipitate is dissolved in DMF and treated with 1.5 equivalents of (6) and heated for 30 min under reflux. The reaction mixture is then allowed to cool to room temperature and the product hydrolyzed by addition of 10 ml of 5% isopropanol and heating for 15 min under reflux. Evaporation of the solvent yields a syrup-like oil from which the azepine (9a) is isolated by chromatography in 70% yield.-@) and (10) were prepared under analogous reaction conditions in comparable yields.
Of particular interest are the syntheses of the o-bis(trimethy1silyl) derivatives ( 3 r ) and ( 4 e ) . Although quite strained, these compounds form in relatively high yield because bistrimethylsilylacetylene does not trimerize under the reaction conditions[ld. 91. Thus, slow addition of the diyne (1) to the alkyne ( 2 ) in this case leads to more efficient cocyclization, although side reactions are not entirely suppressed.
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