Isoxazoline derivatives. Part VI. Regioselectivity in the 1,3-dipolar cycloaddition of nitrile oxides to αβ-unsaturated ketones

1,3-Cycloadditions of nitrile oxides to αβ-unsaturated ketones have been studied. In most cases a mixture of the two regioisomeric 3-substituted 4- and 5-acyl-Δ2-isoxazolines was obtained. The individual compounds were characterised by chemical and/or spectroscopic methods. Effects of steric and electronic factors on the cycloadditions are discussed.