Abstract 2-Bromo-3-methyl-1,4-naphthoquinone and 2-methyl-1,4-naphthoquinone are highly reactive species known to dimerize in various ways. The product obtained in the dimerization of each compound is primarily dependent upon the solvent used.… Click to show full abstract
Abstract 2-Bromo-3-methyl-1,4-naphthoquinone and 2-methyl-1,4-naphthoquinone are highly reactive species known to dimerize in various ways. The product obtained in the dimerization of each compound is primarily dependent upon the solvent used. Ionic liquids represent a new class of solvents having non-molecular (ionic) character. Replacement of a conventional organic solvent with an ionic solvent frequently changes the mechanism of a reaction. In this study, reactions of 2-bromo-3-methyl-1,4-naphthoquinone and 2-methyl-1,4-naphthoquinone in ionic liquids were examined. Dimerization of 2-bromo-3-methyl-1,4-naphthoquinone or 2-methyl-1,4-naphthoquinone with N-methylcyclohexylamine in tetra-n-butylammonium bromide (TBAB), an ionic liquid, under an aerobic atmosphere afforded 5,7,12,14-pentacenetetrone and 1-methylKuQuinone, respectively. The use of TBAB as a solvent improved the yields of the products as compared with previously reported methods. The mechanism of each dimerization was also investigated.
               
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