Facile synthesis of isoquinolines and isoquinoline N-oxides via a copper-catalyzed intramolecular cyclization in water

A highly efficient method for the facile access of isoquinolines and isoquinoline N-oxides via a Cu(i)-catalyzed intramolecular cyclization of (E)-2-alkynylaryl oxime derivatives in water has been developed. This protocol was performed under simple and mild conditions without organic solvent, additives or ligands. By switching on/off a hydroxyl protecting group of oximes, the selective N-O/O-H cleavage could be triggered, delivering a series of isoquinolines and isoquinoline N-oxides, respectively, in moderate to high yields with good functional group tolerance and high atom economy. Moreover, the practicality of this method was further demonstrated by the total synthesis of moxaverine in five steps.

Automated summary

In this study, a Cu(i)-catalyzed intramolecular cyclization reaction in water was developed for the synthesis of isoquinolines and isoquinoline N-oxides. The reaction conditions were simple and mild, without the need for organic solvents, additives, or ligands. By modifying the protecting group of oximes, selective N-O/O-H cleavage could be achieved, producing the desired products in moderate to high yields with good functional group tolerance and high atom economy. The practicality of this method was further demonstrated by the total synthesis of moxaverine.