jodering

Jodering, or iodination, is the chemical process of introducing iodine into an organic molecule. It is used to form organoiodine compounds that can serve as versatile intermediates in further transformations, or as labels in biological and medical contexts.

In organic synthesis, jodering occurs mainly by electrophilic iodination of electron-rich substrates or by radical iodination of less activated substrates. Electrophilic iodination relies on an activated iodine species (I+) generated from molecular iodine in the presence of an oxidant or catalyst, often favoring positions directed by electron-donating substituents. In aromatic systems, activated rings such as those bearing methoxy or hydroxy groups show enhanced reactivity and characteristic regioselectivity, typically yielding iodinated products at the ortho and/or para positions relative to activating groups. Radical iodination uses radical sources and iodine to add across multiple bonds in alkanes or alkenes, producing iodinated derivatives under milder conditions.

Jodering has broad applications. It is a common step in the synthesis of pharmaceutical intermediates, natural products, and materials where C–I bonds enable subsequent cross-coupling reactions. Radiolabeled iodination uses isotopes such as I-123, I-125, or I-131 to tag biomolecules for diagnostic imaging or therapy in medicine.

Considerations in jodering include selectivity, functional-group tolerance, and the lability of C–I bonds under subsequent conditions. Iodinated products can be more reactive in cross-coupling than their brominated or chlorinated analogs, yet the reactions can require careful handling due to the oxidizing reagents and the potential toxicity of iodine reagents.