Dimerizations of 2-bromo-3-methyl-1,4-naphthoquinone and 2-methyl-1,4-naphthoquinone in tetra-n-butylammonium bromide

Mai Onuki, Motohiro Ota, Shoya Otokozawa, Shogo Kamo, Shusuke Tomoshige, Kazunori Tsubaki, Kouji Kuramochi

Research output: Contribution to journalArticle

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.

Original languageEnglish
Article number130899
JournalTetrahedron
DOIs
Publication statusAccepted/In press - 1 Jan 2019

Keywords

  • 1,4-Naphthoquinone
  • 1-MethylKuQuinone
  • 5,7,12,14-Pentacenetetrone
  • Dimerization
  • Ionic liquid

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