Abstract
The reaction of di-tert-butyl selenoketone with propiolic acid gave 2H,6H-1,3-oxaselenin-6-one in 78% yield, whereas the reaction of di-tert-butyl thioketone with propiolic acid recovered starting thioketone almost quantitatively. On the other hand, the reaction of selenofenchone with propiolic acid gave 2H,6H-1,3-oxaselenin-6-one and Wagner-Meerwein rearranged product in good yields.