Metal-free synthesis of carboxamides via the Lossen rearrangement

A novel and efficient method for synthesizing carboxamides has been developed, utilizing a base-promoted Lossen rearrangement of hydroxylamine derivatives. In these reactions, the hydroxylamine derivatives are bench-top stable and easy to handle, allowing them to smoothly replace highly toxic isocyanate reagents by generating isocyanates in situ. This approach facilitates the straightforward formation of C-P, C-C, or C-N bonds. Furthermore, the mild reaction conditions, straightforward operational procedure, and broad substrate scope render this protocol highly practical and attractive.