Utilizing o-quinone methide chemistry: synthesis of sterically hindered acridin-4-ols

Three new sterically hindered acridin-4-ols have been prepared by alkylation of anilines with 3,5-di-tert-butyl-6-methoxymethylcatechol followed by oxidation of the reaction mixture. Formation of the acridine moiety was found to occur in the course of oxidation of the intermediate (anilinomethyl)catechol on contact with air in the Et₂O/H₂O–KOH system. The molecular structure of two acridin-4-ols was determined by single-crystal X-ray diffraction.