Synthesis and Plane Selective Spin Trapping of a Novel Trap 5,5-Dimethyl-3-(2-ethoxycarbonylethyl)-1-pyrroline N-oxide

Abstract

A novel cyclic nitrone spin trap 5,5-dimethyl-3-(2-ethoxycarbonylethyl)-1-pyrroline N-oxide has been prepared and its ability to trap a series of transient free radicals has been investigated. This nitrone scavenges free radicals to give persistent nitroxides, e.g., the half life-times of hydroxyl radical adducts and tert-butoxy radical adducts in benzene >30 min, and the life-time of acetyl adducts >60 min. The EPR spectrum of 2,2-dimethyl-4-(3-hydroxypropyl)pyrrolidinyl-1-oxyl aminoxyl shows that the hyperfine splitting constants of two β-hydrogens are equal to 14.58 G and 23.29 G respectively, i.e., the two β-hydrogens are not magnetically equivalent. Radical addition to the nitrone is probably plane selective affording only one of the two possible geometric isomer pairs of the spin adduct nitroxides. The trans approach mechanism is proposed through configuration and conformation analysis.