Chiral iodanes for asymmetric oxygen-atom (and carbon-atom) transfer in biomimetic dearomative transformations of phenols
Institute of Molecular Sciences
University of Bordeaux
Wednesday, October 3, 2018
C2-361 (Reading Room)
Abstract: The chemistry of hypervalent organoiodine compounds, also referred to as iodanes, has unarguably experienced an impressive development since the early 1990s, as evidenced by both the diversity of iodane reagents that are available today and the number of chemical transformations that these metal-free reagents can promote. Major current research efforts focus on the design of chiral l3- and l5-iodane structures for asymmetric synthesis and organoiodine-catalyzed versions thereof.
The focal reaction of our own contributions to this field has been the dearomatization of phenols, which constitutes a powerful tactic for the rapid construction of highly functionalized molecular architectures, and often an ultimate key transformation in the biogenesis of numerous natural products. In particular, ortho-quinonoid cyclohexa-2,4-dienones can be efficiently generated by iodane-mediated oxygenative phenol dearomatization during which the iodane reagent regioselectively transfers an oxygen atom at a substituted ortho-carbon center of an appropriate starting phenol. Novel chiral l5-iodanes were developed to control the configuration of this carbon center upon its sp2 to sp3 hybridization change, and these reagents were successfully utilized in the asymmetric and biomimetic synthesis of, inter alia, bis(thymol), bacchopetiolone, and the polar head of scyphostatin.
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