“…Leuco-quinizarin, characterized by its highly active diketone skeleton, serves as a versatile reactant capable of functioning as both an electrophile and a nucleophile. Its efficient conversion into a wide range of compounds has been recognized since Marschalk’s discovery in 1936. ,,,,,,,, Several methodologies for the synthesis of leuco-quinizarin from quinizarin, a readily available and cost-effective substrate, involve the use of stoichiometric amounts of inorganic reductants and bases or acids, such as sodium hydrosulfite (dithionite) bases, ,,,,,,,,,,,, Al(0) or Zn(0) acids, CuCl 2 acids, Fe 2+ acids, and SnCl 2 acids in most cases (Figure a). Although these synthetic methods have been widely used, large amounts of waste or toxic gas from stoichiometric reductants are generated; moreover, neutralization is required during the workup process.…”