Direct use of hydroxyl ions as an oxygen source for oxidation of isoquinolinium salts to isoquinolinones in water solution

Abstract

Environmentally friendly synthesis of isoquinolinones and quinolinones has been achieved in water solution by oxidation of isoquinolinium and quinolinium salts using oxygen under mild conditions. This reaction is compatible with numerous isoquinolinium and quinolinium salts. The results of the isotope labeling experiment (using ¹⁸O₂ and H₂¹⁸O) suggest that OH⁻ is the oxygen source of the forming products, and oxygen serves as the oxidant. Moreover, this method can be used to synthesize bioactive molecules such as a topoisomerase I inhibitor.