Cobalt(III)-catalyzed synthesis of isoquinolines from oximes and alkynes in deep eutectic solvents

A cobalt-catalyzed redox-neutral [4 + 2] annulation of oximes and alkynes in deep eutectic solvents comprising quaternary ammonium compounds and hydrogen bond donors has been developed, the best system being Me₃N+CH₂CO₂- / HOCH(CF₃)₂. No external oxidizing reagent was required, and only water was generated as the secondary product. The catalytic system can be reused in three consecutive cycles.