The diverse biological activities of tocopherols and their analogs have inspired considerable interest in the development of routes for their efficient asymmetric synthesis. Here, we report that chiral ammonium hypoiodite salts catalyze highly chemo- and enantioselective oxidative cyclization of γ-(2-hydroxyphenyl)ketones to 2-acyl chromans bearing a quaternary stereocenter, which serve as productive synthetic intermediates for tocopherols. Raman spectroscopic analysis of a solution of tetrabutylammonium iodide and tert-butyl hydroperoxide revealed the in situ generation of the hypoiodite salt as an unstable catalytic active species and triiodide salt as a stable inert species. A high-performance catalytic oxidation system (turnover number of ~200) has been achieved through reversible equilibration between hypoiodite and triiodide in the presence of potassium carbonate base. We anticipate that these findings will open further prospects for the development of high-turnover redox organocatalysis.

https://science.sciencemag.org/content/sci/345/6194/291.full.pdf

High-turnover hypoiodite catalysis for asymmetric synthesis of tocopherols

Molecular Iodine Catalyzed Cross-Dehydrogenative Coupling Reaction between Two sp3 C–H Bonds Using Hydrogen Peroxide

The effects of dimethyl sulfide (DMS) and methyl iodide (MI) emissions are analyzed using a two-dimensional photochemical model of a marine tropical tropospheric synoptic system. The model traces the atmospheric transformation cycles of the emissions to aerosols. The study is focused on remote tropical ocean regions and includes simulations of the spatial and diurnal variations of various iodine and sulfur species, and the species OH, HO2, and H2O2. One line of analysis leads to the conclusion that the reaction IO + DMS yields DMSO + I may play a significant role in destroying DMS if it proceeds at the published fast rate. Alternative lines of analyses are presented.

Are there interactions of iodine and sulfur species in marine air photochemistry

Molecular iodine has been used for more than 100 years as a remarkable catalyst for many organic transformations such as cycloadditions, Michael and aldol reactions, or esterifications. Different explanations for the origin of its catalytic effect have been proposed in the last decades including a "hidden" Bronsted acid catalysis by HI, a Lewis-acid (or halogen-bond) activation, or catalysis by an iodonium(I) species. Recently, iodine catalysis again gained more interest due to the latest developments in halogen-bond catalysis. In this Minireview, we first summarize the experimental basis for the proposed modes of activation. Subsequently, we analyze typical iodine-catalyzed reactions to gain more insights into the underlying reaction mechanisms.

Mechanisms in Iodine Catalysis.

Hypoiodous acid: kinetics of the buffer-catalyzed disproportionation

Electronic spectra are reported for the hypoiodite ion (OI−), hypoiodous acid (HOI), and its conjugate acid (H2OI+) in aqueous media. Iodine in the +1 oxidation state was produced by either of the ...

Jean Paquette

Papers

Iodine chemistry in the +1 oxidation state. I. The electronic spectra of OI−, HOI, and H2OI+

The radiolysis of iodine in aqueous solutions containing methane