Preparation and nitrosation of 3,4‐dimethyl‐3‐penten‐2‐one ( e )‐ and ( z )‐oximes. Formation of 3,3,4,5‐tetramethyl‐3 H ‐pyrazole 1,2‐dioxide and of 2‐isoxazoline derivatives

The stereoisomeric ( E )‐ and ( Z )‐oximes of 3,4‐dimethyl‐3‐penten‐2‐one were prepared and nitrosated with butyl nitrite in methanol. The ( E )‐oxime gave 3,3,4,5‐tetramethyl‐3 H ‐pyrazole 1,2‐dioxide in nearly quantitative yield, while the ( Z )‐oxime reacted less readily, giving a lower yield of the same product, with five other products identified as isoxazoline derivatives. Three of these were 4‐hydroxy‐, 4‐methoxy‐, and 4‐nitro‐3,4,5,5‐tetramethyl‐2‐isoxazoline. The fourth was the O ‐(3,4,5,5‐tetramethyl‐2‐isoxazolin‐4‐yl) derivative of the starting ( Z )‐oxime, and the fifth was 4‐methylene‐3,5,5‐trimethyl‐2‐isoxazoline.