Synthesis of 4‐Oxo‐3a,4,5,6‐tetrahydroimidazo[1,5‐b]isoxazole‐3‐carboxylic Acid Esters

3‐Imidazoline 3‐oxides react regioselectively with 3‐phenylpropanoic acid alkyl esters to give the corresponding 2‐phenyl‐3a,4,5,6‐tetrahydroimidazo[1,5‐b]isoxazole‐3‐carboxylic acid alkyl esters. This adducts convert to imidazole and the corresponding alkyl 3‐oxo‐3‐phenylpropanoic acid esters when treated with alkoxides or heated under vacuum. Attempts to oxidise the carbon–carbon double bond using KMnO4–FeSO4 led to the formation of heretofore unknown 4‐oxo‐3a,4,5,6‐tetrahydroimidazo[1,5‐b]isoxazoles.