New Chiral Iodine(III) reagents for stereoselective synthesis

With increasing demands for developing environmentally friendly synthetic approaches, hypervalent iodine compounds have attracted great attention in the synthetic community due to their low toxicity, environmental sustainability and unique reactivity. This work outlines the synthesis and use of rarely investigated hypervalent iodine reagents of the type IL3 (L = heteroatom-containing ligand) for an improved awareness of its reactivity. Iodine tricarboxylates enable fast and efficient access to (dicarboxyiodo)arenes including previously inaccessible compounds. This novel procedure provides a significant advantage over current methodologies, since the (dicarboxyiodo)arenes were conveniently prepared in one-pot operations and employed in subsequent reactions without further purification. The chemistry of iodine tricarboxylates was extended to ligand exchanges with heteroatom-containing ligands, which furnished novel hypervalent iodine compounds of the type IL3.[1] The synthesis of iodine tricarboxylates requires the use of nitric acid for the oxidation of iodine to iodine(III). Therefore, Oxone® was employed for the development of a more environmentally conscious alternative synthetic approach towards iodine triacetate. However, Oxone® furnished iodine monoacetate instead, which in turn was applied in a highly efficient regio- and diastereoselective 1,2-iodoacetoxylation of various alkenes and selected alkynes in a one-pot procedure.[2] viii Moreover, iodine triacetate was an extremely beneficial iodinating reagent in the synthesis of a novel class of hypervalent iodine(III) reagents containing a rigid chiral α-tetralol scaffold. However, the utilisation of these enantiomerically pure reagents in stereoselective transformations revealed only moderate enantioselectivities.[3] Finally, the synthesis of lactamide/resorcinol-based hypervalent iodine(III) reagents and their applications as organocatalysts in the asymmetric catalytic α-acetoxylation of ketones was investigated. The prior transformation of the ketones to easily accessible acetyl enol ethers was advantageous and enantiomeric excesses up to 88% were obtained by I(I)/I(III) catalysis using chiral iodoarene Ar*I in combination with mCPBA and acetic acid.[4