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Keywords:

  • 1,4-naphthoquinone sulfides;
  • C[BOND]C coupling;
  • C[BOND]S coupling;
  • green chemistry;
  • laccase

Abstract

Oxidative C[BOND]S and C[BOND]C bond formation with aryl and alkyl thiols was catalyzed under mild conditions in a reaction vessel open to air at pH 4.5 in the presence of a commercial laccase (Novozym 51003 or Suberase) and a cosolvent (DMF) to afford 1,4-naphthoquinone sulfides. Although both monothiolation and dithiolation of the 1,4-naphthohydroquinone were accomplished, the latter was favored. In addition, unprecedented dimerization of monothiolated intermediates occurred through C[BOND]C coupling. These commercial laccases provide a facile and a more environmentally friendly synthetic approach to both 1,4-naphthoquinone sulfides and 1,4-naphthoquinone sulfide dimers.