No abstract

The synthesis and structural characterization of a hitherto unknown tetradehydrodinaphtho[10]annulene, which had eluded isolation since attempts initiated during the late 1960s, was achieved. Moreover, the dehydroannulene was transformed into stable derivatives of zethrene, which was first reported in 1955, but forgotten for a long time. These molecules are substituted at the 7,14-positions and open the door to the zethrene family for potential application as optoelectronic materials.

The synthesis and structural characterization of hitherto unknown tetradehydrodinaphtho[10]annulene, a hydrocarbon whose synthesis had been attempted four decades ago, was achieved for the first time. Moreover, the dinaphtho[10]annulene was transformed smoothly into stable zethrene derivatives substituted at its 7,14-positions, showing that it serves as a good reservoir of zethrene derivatives. Optical and electrochemical properties of a disubstituted zethrene derivative are also presented.

Diindenopyrene 4b and its diastereomer, which are extended homologues of 1,6- and 1,8-pyrenoquinodimethanes fused by indene units, respectively, were synthesized by reaction of 1,4,5,8-tetrakis(mesitylethynyl)naphthalene (7) with bis(2,4,6-trimethylpyridine)iodine(I) hexafluorophosphate via cationic cyclization mechanisms at both centers of reaction. Unexpectedly, reaction of 7 with iodine, a reagent that typically gives products of cationic cyclization, gave cycloheptapentalenoindenophenalene derivative 9b and its diastereomer incorporating an azulene unit at one end of the π framework, via two different modes (radical and cationic) of cyclization at each reaction site. The physical properties of the products are presented, and the dual modes of cyclization of 7 and its model compound with only one reaction center are discussed.

Zethrene wurden durch Pd‐katalysierte Cyclodimerisierung von 1‐Ethinyl‐8‐iodnaphthalenen synthetisiert (siehe Schema). Die Strukturen dieser Cycloaddukte wurden durch Röntgenstrukturanalyse bestätigt, wobei die Bindungslängen offenbaren, dass die zwei zentralen sechsgliedrigen Ringe der Titelverbindung nicht aromatisch sind.