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—

Abstract

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.