Regioselectivity in the 1,3-dipolar cycloaddition of nitrile oxides to N-(3,5-dichlorophenyl)itaconimide

Summary The regioselectivity of the nitrile oxide cycloaddition with 3,3-methylene-1-(3,5-dichlorophenyl)-2,5-pyrrolidindione (1) is discussed. Arylnitrile oxides add regioselectively to the carboncarbon double bond of1, giving exclusively spiro-isoxazolines3a–k, whereas acetonitrile oxide gives both adducts3l and4l. AM1 calculations of the reactants and cycloadducts were performed, the regiochemistry of the cycloaddition seems to be controlled by steric effects. Reduction of3a with NaBH₄ in the presence of magnesium perchlorate at –20 °C was regio-and stereoselective to yield the hydroxylactams9a and10a, whereas hydroxymethylisoxazoline14a was obtained in the absence of Mg(ClO₄)₂.Part XXX in the series 1,3-Dipolar Cycloaddition on Heterocycles. Part XXIX 27]