Synthesis of Polysubstituted Iodoarenes Enabled by Iterative Iodine-Directed para and ortho C-H Functionalization.

Among halogenated aromatics, iodoarenes are unique in their ability to produce the bench-stable halogen(III) form. Earlier, such iodine(III) centers were shown to enable C-H functionalization ortho to iodine via halogen-centered rearrangement. The broader implications of this phenomenon are explored by testing the extent of an unusual iodane-directed para C-H benzylation, as well as by developing an efficient C-H coupling with sulfonyl-substituted allylic silanes. Through the combination of the one-shot nature of the coupling event and the iodine retention, multisubstituted arenes can be prepared by sequentially engaging up to three aromatic C-H sites. This type of iodine-based iterative synthesis will serve as a tool for the formation of value-added aromatic cores.