The Vilsmeier-Haack reaction on isoxazolin-5-ones gives 2-(dialkylamino)-l, 3-oxazin-6- ones, and a reaction path is proposed depending on substitution pattern of the isoxazolin-5- ones studied. A thermal equilibrium between the oxazinones, imino ketenes, and vinyl isocyanates is hypothesized to explain most of the chemical reactivity of the 2-(dialkylamino)- 1, 3-oxazin-6-ones.
