Metal-Free Cross-Dehydrogenative Coupling (CDC): Molecular Iodine as a Versatile Catalyst/Reagent for CDC Reactions

The development of ecofriendly methods for carbon-carbon (C-C) and carbon-heteroatom (C-Het) bond formation is of great significance in modern-day research. Metal-free cross-dehydrogenative coupling (CDC) has emerged as an important tool for organic and medicinal chemists as a means to form C-C and C-Het bonds, as it is atom economical and more efficient and greener than transition-metal catalyzed CDC reactions. Molecular iodine (I-2) is recognized as an inexpensive, environmentally benign, and easy-to-handle catalyst or reagent to pursue CDCs under mild reaction conditions, with good regioselectivities and broad substrate compatibility. This review presents the recent developments of I-2-catalyzed C-C, C-N, C-O, and C-S/C-Se bond-forming reactions for the synthesis of various important organic molecules by cross-dehydrogenative coupling.