An Efficient Preparation and Characteristic Properties of Tetramethyl 3,3',3'',3'''-
(p-Quinodimethane-7,7,8,8-tetrayl)tetraazulene- 1,1',1'',1'''-tetracarboxylate

Shin-ichi TAKEKUMA*, Masato SASAKI, Hideko TAKEKUMA and Hiroshi YAMAMOTO

Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University; 3-4-1, Kowakae, Higashi-Osaka-shi 577-8502 Japan
Department of Chemistry, Okayama University; 3-1-1 Tsushima-naka, Okayama-shi 700-8530 Japan

Reaction of methyl 1-azulenecarboxylate (1) with a 0.25 molar amount of terephthalaldehyde in acetic acid in the presence of hydrochloric acid at room temperature (25 C) for 2 h under aerobic conditions gives tetramethyl 3,3',3'',3'''-[1,4-phenylenebis(methylidyne)]tetraazulene-1,1',1'',1'''-tetracarboxylate (2) in a good yield (92%), which upon oxidation with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) in chloroform quantitatively affords the title compound 3 as the first example of 7,7,8,8-tetra(1-azulenyl)-p-quinodimethane derivatives. Structures of these products were established on the basis of their spectroscopic data (UV/VIS, IR, MS, 1H- and 13C-NMR). A plausible reaction pathway for the formation of those compounds is discussed. The characteristic properties (i.e., TGA/DTA and CV/DPV) are also described for compound 3, which upon reaction with electron acceptors [i.e., tetracyanoethylene (TCNE), 7,7,8,8-tetra(1-azulenyl)-p-quinodimethane (TCNQ), and DDQ] in dichloromethane rapidly gives the corresponding charge transfer (CT) complexes. Along with these data, a result of the semiempirical molecular orbital calculation (WinMOPAC V2.0, the semiempirical Hamiltonian: AM1) for compound 3 is shown.
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