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.