抄録
As a new method to generate highly reactive polyynes, we synthesized dialkynylmethylenebicyclo[4.3.1]deca-1,3,5-triene derivatives which would form linear polyynes via dialkynylvinylidenes by [2+1] cycloreversion. Herein, we report the synthesis and cheletropic fragmentation of the macrocyclic oligomers of the bicyclotriene derivatives to the corresponding cyclo[n]carbons, monocyclic forms of carbon clusters. The macrocyclic oligomers, which have expanded radialene structures, were prepared by copper(II)-mediated oxdative coupling of the diethynylbicyclotrienes under dilute conditions. In the electronic spectra of the radialenes, the absorption dose not exhibit bathochromic shift with increasing ring size of the macrocycles, indicating cross conjugative interactions of the ene-yne-yne-ene chromophores. Laser-desorption mass spectra of the expanded radialenes exhibit, in the negative mode, peaks due to the corresponding cyclo[n]carbon anions (n=18, 24, 30 and 36) formed by the loss of aromatic indan fragments.
