Laccase-catalyzed C-S and C-C coupling for a one-pot synthesis of 1,4-naphthoquinone sulfides and 1,4-naphthoquinone sulfide dimers

Abstract

Oxidative C-S and C-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-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.