Unveiling the mechanism of the iodane-guided ortho C-H allylation

A metal-free C-H allylation strategy is described to access diverse functionalized ortho-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 resulting ortho-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 the trans-product formation.

This paper is the result of a joint collaboration with the groups of Prof. A. Shafir of the Institute for Advanced Chemistry of Catalonia, Prof. A. B. Cuenca of the Químics de Sarri , Prof. S. Lethu of the Institute of Chemical Research of Catalonia, and Prof. J. Zhu from Xiamen University; our group has performed the DFT mechanistic study with a great work by Dandan Chen. The paper was published recently in Angewandte Chemie:

W.W. Chen, A. Cunillera, D. Chen, S. Lethu, A. Lñpez de Moragas, J. Zhu, M. Sol , A.B. Cuenca, and A. Shafir
“Iodane-Guided ortho C-H Allylation”
Angew. Chem. Int. Ed. 2020, ASAP-
DOI: 10.1002/anie.202009369

Girona, September 3, 2020
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