Stereo- and regio-selectivity in acetonitrile oxide cycloaddition to norethisterone acetate

Acetonitrile oxide underwent a 1,3-dipolar cycloaddition with 17-acetate norethisterone affording the expected isoxazoline and isoxazoles derivatives in good yields. Mono- and bis-cycloadducts were obtained and the structures of the new compounds were elucidated based on the corresponding analytical and spectroscopic data, which were presented and discussed in detail. The stereo- and regio-chemical outcome of the cycloadditions was also accounted on the basis of 1,3-dipolar cycloaddition theory. Frontier Orbital theory (FO) and steric effects are assessed in orienting the selectivity in the cycloaddition to steroids.