Synthesis of Arylthiobenzothiazoles via a Copper(I)-Catalyzed S-Arylation

Significance

Reported are the first one-pot, intra- and intermolecular S-arylations via copper(I) catalysis leading to the direct synthesis of aryl­thiobenzothiazoles. In this single catalytic one-pot double arylation strategy, intramolecular S-arylation of dithiocarbamate salt 1 afforded benzothi­azol-2-thiol (MBT) as intermediate 3 (confirmed by isolation), which undergoes an intermolecular C-S coupling giving 2-arylthiobenzothiazoles 4 directly. After screening of ligands, L1 was found to be ­optimal in terms of yield and short reaction time under an air atmosphere (no disulfide formation). This catalytic system for double S-alkylation is ­effective for aryl iodides bearing EWG and EDG substituents. However, the presence of EWGs ­accelerates the rate of reaction (intermolecular) giving products in shorter times, whereas EDGs retard the reaction. Moreover, bromo- and chloro-arenes were not effective as intermolecular coupling partners.

Review: T. Kondo, T.-a. Mitsudo Chem. Rev. 2000, 100, 3205-3220.