Synthesis Of 1,3-Diazaheterocyclic Skeletons Via Oxidative C–N Bond Construction

1,3-Diazaheterocyclic skeletons, such as, quinazolinones, benzimidazoles, and imidazopyridines, widely exist in many natural products and bioactive synthetic compounds. The general strategy for the synthesis of quinazolinones and benzimidazoles is condensation of diamino compounds with aldehydes, followed by transition-metal-catalyzed or oxidant-mediated oxidative cyclization. The available synthetic methods are associated with disadvantages, such as harsh reaction conditions, expensive or toxic reagents, and/or limited reaction scopes. Therefore, development of facile and efficient methodologies to construct these nitrogen-containing heterocyclic copounds is of important value.In this dissertation, we have developed two molecular iodine-mediated oxidative C–N bond construction reactions to synthesize quinazolinone, benzimidazole, and imidazopyridine derivatives. Starting with diamino compounds and aldehydes, 39 quinazolinones and benzimidazoles were efficiently synthesized in 59–99% yields via I2-mediated one-pot annulation. Addition intermediates of 2-aminopyridines to nitriles were directly subject to the I2/KI-mediated oxidative cyclization reaction conditions to afford 22 imidazo[1,2-a]pyridin-2-amines in 47–99% yields.All the products have been characterized by 1H, 13 C NMR, and HRMS. Some of them were further comfirmed by X-ray single-crystal diffraction. The features of these two new oxidative cyclization reactions include simple operation procedures, mild reaction conditions, high yields, broad substrate scopes, which provides facile access to a variety of 1,3-diazaheterocyclic derivatives.