Transition-metal-catalyzed nitrene-transfer reactions are powerful methods for incorporating nitrogen atoms directly into organic molecules. [1,2] Organic azides [2a,b] and N-sulfonyliminoiodinanes [2c-e] are highly reactive nitrene precursors, and have been widely used for such reactions as olefin aziridination and C À H amination. However, they must be handled carefully or prepared immediately before use because of their high reactivity. Therefore, the development of catalytic nitrene-transfer reactions that use stable precursors under mild reaction conditions is an important topic. Our research interest has been focused on 4H-isoxazol-5-ones, five-membered cyclic oxime esters, as candidates for stable vinylnitrene equivalents (Scheme 1). They can be readily prepared from bketoesters [3] and are generally thermally stable. We envisioned that the reaction of a 4H-isoxazol-5-one with a palladium catalyst would give a nitrene complex, [4] which is formed by the activation of the N À O bond by a low-valent palladium species [5] followed by decarboxylation. Herein, we report a palladium-catalyzed decarboxylative intramolecular aziridination reaction of alkene-tethered 4H-isoxazol-5-ones to form N-fused bicyclic aziridines.During the course of our investigations of several nitrenetransfer reactions using 4H-isoxazol-5-ones, we found that the reaction of 4H-isoxazol-5-one 1 a, which possesses a methallyl group at the 4-position, in the presence of 2.5 mol % of [Pd 2 (dba) 3 ] (5 mol % Pd) and 10 mol % of PPh 3 in 1,4-dioxane at 80 8C for 12 h gave the expected 1-azabicyclo[3

Transition-metal-catalyzed nitrene-transfer reactions are powerful methods for incorporating nitrogen atoms directly into organic molecules. [1,2] Organic azides [2a,b] and N-sulfonyliminoiodinanes [2c-e] are highly reactive nitrene precursors, and have been widely used for such reactions as olefin aziridination and C À H amination. However, they must be handled carefully or prepared immediately before use because of their high reactivity. Therefore, the development of catalytic nitrene-transfer reactions that use stable precursors under mild reaction conditions is an important topic. Our research interest has been focused on 4H-isoxazol-5-ones, five-membered cyclic oxime esters, as candidates for stable vinylnitrene equivalents (Scheme 1). They can be readily prepared from bketoesters [3] and are generally thermally stable. We envisioned that the reaction of a 4H-isoxazol-5-one with a palladium catalyst would give a nitrene complex, [4] which is formed by the activation of the N À O bond by a low-valent palladium species [5] followed by decarboxylation. Herein, we report a palladium-catalyzed decarboxylative intramolecular aziridination reaction of alkene-tethered 4H-isoxazol-5-ones to form N-fused bicyclic aziridines.During the course of our investigations of several nitrenetransfer reactions using 4H-isoxazol-5-ones, we found that the reaction of 4H-isoxazol-5-one 1 a, which possesses a methallyl group at the 4-position, in the presence of 2.5 mol % of [Pd 2 (dba) 3 ] (5 mol % Pd) and 10 mol % of PPh 3 in 1,4-dioxane at 80 8C for 12 h gave the expected 1-azabicyclo[3

A decarboxylative intramolecular aziridination reaction of alkene‐tethered isoxazol‐5‐ones with a palladium/phosphine catalyst gives N‐fused bicyclic aziridines which readily react with various reagents to afford ring‐opened pyrroline derivatives.