Bronsted Acids Enable Three Molecular Rearrangements of One 3-Alkylidene-2&ITH&IT-1,2-oxazine Molecule into Distinct Heterocyles

This work describes three different strategies to structurally rearrange one 3-alkylidene-2H-1,2-oxazine molecule into three distinct heterocycles using HOTf, propiolic acid, and silica gel, respectively. The mechanisms of these rearrangement reactions involve three independent routes, including (i) Bronsted acid catalysis, (ii) a synergetic action of Bronsted acids and anions, (iii) a surface-directed chemoselectivity.