Introducing N-X Anomeric Amides: Powerful Electrophilic Halogenation Reagents

Electrophilic halogenation is a widely-used tool employed by medicinal chemists to either pre-functionalize molecules for further diversity or incorporate a halogen atom in drugs or drug-like compounds to solve metabolic problems or modulate off-target effects. Current methods to increase the power of halogenation rely either on the invention of new reagents or activating commercially available reagents with various additives such as Lewis/Brønsted acids, Lewis bases and hydrogen bonding activators. There is a high demand for new reagents that can halogenate otherwise unreactive compounds under mild conditions. Herein we report the invention a new class of powerful halogenating reagents based on anomeric amides, taking advantage of the energy stored in the pyramidalized nitrogen of N-X anomeric amides as a driving force. These robust halogenating methods are compatible with a variety of functional groups and heterocycles, as exemplified on over 50 compounds (including 13 gram-scale examples and 1 flow chemistry scale-up). Their high halogenating prowess is also demonstrated in other reactivity contexts. A DFT computational study supports the defining role of the anomeric amide motif.