An efficient method for the construction of 1,2‐oxazine N‐oxides has been developed via Pd‐catalyzed chemoselective bis‐allylic substitution of 2‐methylenepropane‐1,3‐diol dicarbonates with arylated nitroalkanes through sequential C‐ and O‐nucleophilic allylic substitution in one‐pot manipulation. By using Pd(PPh3)4 as a catalyst under mild reaction conditions, the process allows rapid access to 3‐aryl‐5,6‐dihydro‐4H‐1,2‐oxazine N‐oxides in high yields with excellent chemoselectivities.