Ligand-Controlled Regiodivergence in the Copper-Catalyzed [2,3]- and [1,2]-Rearrangements of Iodonium Ylides

Despite the importance
of allylic ylide rearrangements for the
synthesis of complex molecules, the catalyst control of [2,3]- and
[1,2]-rearrangements remains an unsolved problem. We developed the
first regio­divergent [2,3]- and [1,2]-rearrangements of iodonium
ylides that are controlled by copper catalysts bearing different ligands.
In the presence of a 2,2′-dipyridyl ligand, diazo­esters
and allylic iodides react via a [2,3]-rearrangement pathway. Alternatively,
a phosphine ligand favors the formation of the [1,2]-rearrangement
product. A series of α-iodoesters containing a broad range of
functional groups were obtained in high yields, regio­selectivities,
and diastereo­selectivities. Deuterium-labeling studies suggest
distinct mechanisms for the regio­selective rearrangements.