Thomas Wirth

The impressive development of hypervalent iodine chemistry in recent years is reflected by the number of publications in this area. Although the synthesis of the first hypervalent iodine compound dates back more than 100 years, the investigation of the reactivities of these compounds and their efficient use as metal-free reagents in organic synthesis is still ongoing. This contribution summarizes recent achievements and highlights key findings and developments that will influence future research and lead to novel applications of hypervalent iodine reagents in synthesis.

A dash of iodine: Different reactions relying on the power of hypervalent iodine reagents can now be performed with catalytic amounts of these compounds and a stoichiometric oxidant. Oxidations of alcohols, α-functionalizations of ketones, and spirocyclizations of phenol derivatives are possible.

Selenium goes green! Recent advances in organoselenium chemistry clearly demonstrate that selenium-based catalysts can be used conveniently in a series of functional group transformations. Organoselenium compounds are promising “green catalysts” as they can transfer oxygen from environmentally friendly oxidants such as H2O2.

Hypervalent iodine chemistry is now a well-established area of organic chemistry. Novel hypervalent iodine reagents have been introduced in many different transformations owing to their mild reaction conditions and environmentally friendly nature. Recently, these reagents have received particular attention because of their applications in catalysis. Numerous hypervalent iodine-catalyzed oxidative functionalizations such as oxidations of various alcohols and phenols, α-functionalizations of carbonyl compounds, cyclizations, and rearrangements have been developed successfully. In these catalytic reactions stoichiometric oxidants such as mCPBA or oxone play a crucial role to generate the iodine(III) or iodine(V) species in situ. In this Focus Review, recent developments of hypervalent iodine-catalyzed reactions are described including some asymmetric variants. Catalytic reactions using recyclable hypervalent iodine catalysts are also covered.

Organic synthesis in microreactors is a novel way of performing reactions in a highly controlled way. The benefits of microreactors result from their physical properties, such as enhanced mass and heat transfer as well as regular flow profiles leading to improved yields with increased selectivities.