Reactions of sulfoxonium allylides with nitrile oxides and ring transformations of their reaction products

Reactions of allylides ($\text{1}$) with nitrile oxides ($\text{2}$) afforded furanylglyoxylate oxime ($\text{3}$) and 6H-l,2-oxazine ($\text{4}$). Ring transformations of $\text{3}$ and $\text{4}$ gave $\text{4}$ and pyrrolinone ($\text{6}$), respectively.