Metal-Free Atom-Economical Synthesis of Tetra-Substituted Imidazoles via Flavin-Iodine Catalyzed Aerobic Cross-Dehydrogenative Coupling of Amidines and Chalcones

Herein, we demonstrated the oxidative cross-dehydrogenative coupling between amidines and chalcones catalyzed by flavin and iodine. The riboflavin-iodine catalytic system played multiple roles in substrate-and O-2-activation, enabling the facile and atom-economical synthesis of tetra substituted imidazoles in good yields (60-87%). This metal-free reaction consumed only 1 equiv of molecular oxygen and generated 2 equiv of environmentally benign H2O as the only byproduct.

Automated summary

In this study, the oxidative cross-dehydrogenative coupling reaction between amidines and chalcones catalyzed by flavin and iodine was demonstrated. The riboflavin-iodine catalytic system played multiple roles in substrate and O-2 activation, enabling the facile and atom-economical synthesis of tetra substituted imidazoles in good yields (60-87%). This metal-free reaction consumed only 1 equiv of molecular oxygen and generated 2 equiv of environmentally benign H2O as the only byproduct.