Iodane-GuidedorthoC-H Allylation

A metal-free C-H allylation strategy is described to access diverse functionalizedortho-allyl-iodoarenes. The method employs hypervalent (diacetoxy)iodoarenes and proceeds through the iodane-guided iodonio-Claisen allyl transfer. The use of allylsilanes bearing electron-withdrawing functional groups unlocks the functionalization of a broad range of substrates, including electron-neutral and electron-poor rings. The resultingortho-allylated iodoarenes are versatile building blocks, with examples of downstream transformation including a concise synthesis of the experimental antimitotic core of Dosabulin. DFT calculations shed additional light on the reaction mechanism, with notable aspects including the aromatic character of the transition-state structure for the [3,3] sigmatropic rearrangement, as well as the highly stereoconvergent nature of thetrans-product formation.