A Practical Regioselective Synthesis of Alkylthio- or Arylthioindoles without the Use of Smelly Compounds Such as Thiols

A convenient method for the synthesis of 3-methylthioindoles has been established which does not use smelly compounds such as thiol derivatives. The method, which introduces an alkyl- or arylthio-group into the C3-position of the indole skeleton, was extended to the direct introduction of a methylthio or bromo group at the C2-position using 3-methylthioindoles. No dimerization occurred, and the reaction mechanism was confirmed. The products have the partial structure of potent anti-methicillin-resistant Staphylococcus aureus (anti-MRSA) bromomethylthioindoles (MC 5-8) isolated from marine algae. Furthermore, this reaction could be applied to the synthesis of 3,3-diindolyl thioether which is a core structure of Echinosulfone A.