Hypervalent Iodine and Sulfur‐Mediated CH Functionalization

Abstract

Abstract Hypervalent main group nonmetallic elements, such as iodine and sulfur, have attracted increasing attention owing to their unique reactivities. The facilely interconvertible valencies sometimes render these nonmetallic elements chemical behaviors analogs to transition metals, allowing diverse CH functionalizations to proceed in a green manner. Since their discovery, hypervalent iodine reagents have played a pivotal role in synthetic organic chemistry. Besides their usage as selective oxidants, hypervalent iodine reagents readily participate in single‐electron transfer processes to produce radical cation intermediates, enabling a variety of oxidative carbon–carbon and carbon–heteroatom bond formations. Direct CH functionalization of arenes, alkenes, and alkynes gives rapid access to aryl iodonium salts, which are easily transformed into other functionalities. Similarly, site‐selective CH thianthrenation proceeds smoothly upon suitable activation of sulfoxide reagents. The superior leaving ability and redox properties make the thianthrene moiety an ideal synthetic handle for structural diversifications via transition‐metal and photoredox catalysis. In this article, we focus on the hypervalent iodine and sulfur‐mediated CH functionalizations and describe their applications in carbon–carbon and carbon–heteroatom bond‐forming reactions. The rearrangement‐based CH functionalization will be briefly introduced where possible.