Synthesis of SF5-substituted isoxazolidines using 1,3-dipolar cycloaddition reactions of nitrones with pentafluorosulfanyl acrylic esters and amides

Abstract

1,3-Dipolar cycloadditions of nitrones with pentafluorosulfanyl-substituted acrylic ester and amides afforded new trisubstituted pentafluorosulfanylated isoxazolidines in moderate yields as 4-SF5-regioisomers. Theoretical calculations were carried out and the regioselectivity could be explained by the fact that the 5-SF5-regioisomer probably undertook a spontaneous degradation in the reaction medium via the loss of pentafluorosulfanyl anion. Diastereoselectivity of the 1,3-dipolar cycloadditions was also assessed according to NMR and X-ray diffraction analysis.