Brønsted Acid-Catalyzed Nitroso-Diels–Alder Reaction of 2-Trifluoroacetamido-1,3-dienes

Abstract The nitroso-Diels–Alder (NDA) reaction represents a powerful strategy for the assembly of 3,6-dihydro-1,2-oxazines for nearly a century, owing to its efficiency and broad utility in synthesizing natural products and bioactive molecules. Despite these advancements, traditional NDA reactions are largely limited to neutral 1,3-dienes, while electron-rich 1,3-dienes bearing heteroatom substitutions remain underdeveloped. Herein, we report a Brønsted acid-catalyzed NDA reaction of electron-rich 2-trifluoroacetamido-1,3-dienes with nitrosobenzenes, delivering diverse dihydro-2H-1,2-oxazines in excellent yields. This protocol represents the first NDA reaction of 2-trifluoroacetamido-1,3-dienes.