Reactions of 5-Aminoisoxazoles with α-Diazocarbonyl Compounds: Wolff Rearrangement vs N–H Insertion

A highly chemoselective reaction between 5-aminoisoxazoles and α-diazocarbonyl compounds has been described. Both Wolff rearrangement and N–H insertion products can be obtained selectively by the judicious choice of reaction conditions. In the case of the Wolff rearrangement reactions, the N-isoxazole amides are accessed as the sole products under thermal conditions. On the other hand, α-amino acid derivatives of N-isoxazolescan be obtained through N–H insertion reactions in the presence of catalytic Rh2(Oct)4. Both reactions proceed under mild reaction conditions and feature a broad substrate scope.