A new method for the formation of conjugated polyynes has been developed based on both the rearrangement of vinylidenes to alkynes and the [2+1] cheletropic fragmentation of dialkynylmethylenebicyclo[4.3.1]deca-1,3,5-triene derivatives. A model study of the photolysis of simple dialkynylmethylenebicyclo[4.3.1]deca-1,3,5-trienes resulted in cheletropic fragmentation followed by 1,2-migration to give the corresponding linear polyynes, although undesired isomerization to methylenebicyclo[5.3.0]triene derivatives took place concurrently. Expanded [3]-, [4]-, [5]-, and [6]radialene derivatives with exocyclic bicyclo[4.3.1]decatriene units were prepared by oxidative coupling of the monomeric units as precursors to the corresponding cyclo[n]carbons, monocyclic forms of carbon clusters. The spectroscopic properties of the expanded radialenes were investigated in connection with cross conjugation of the core pi system and with its perturbation by the extraannular bicyclic pi system. In negative-mode laser-desorption time-of-flight (LD-TOF) mass spectra, the expanded radialenes exhibited peaks due to the corresponding cyclo[n]carbon anions (n = 18, 24, 30, and 36) formed by the stepwise loss of the aromatic indane fragments.

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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.