Synthetic Method for the Preparation of Quinazolines by the Oxidation of Amines Using Singlet Oxygen

Abstract An economical method for the preparation of quinazolines by using singlet oxygen as the sole oxidant has been developed. The oxidation of primary amines, such as benzylamine, by singlet oxygen has previously been shown to give products that arise from the rapid nucleophilic addition of amines to imines. To suppress this undesired oxidative coupling reaction, we employed aldehydes as the coupling partners in the preparation of quinazolines. Because of their pharmacological properties such as their sedative, anticonvulsant, and antitussive effects, many different methods have been developed for the efficient synthesis of quinazoline. These include the use of a stoichiometric or excess amount of the oxidant or the use of a transition‐metal catalyst under severe reaction conditions. In contrast, our approach employs visible light, molecular oxygen, and a commercially available photocatalyst, all of which are environmentally friendly.