Synthesis of the cis diastereoisomer of 5-diethoxyphosphoryl-5-methyl-3-phenyl-1-pyrroline N-oxide (DEPMPPOc) and ESR study of its superoxide spin adduct

The cis and trans diastereoisomers of 5-diethoxyphosphoryl-5-methyl-3-phenyl-1-pyrroline N-oxide (DEPMPPO), the C(3)-phenyl analogue of DEPMPO, were prepared in three steps from phenylacetaldehyde and used in ESR-spin trapping of various carbon-, oxygen- and sulfur-centred radicals. In the case of the cis-isomer, the presence of the phenyl group cancels the alternating line width phenomenon observed for the DEPMPO–OOR (R = H, But) spin adducts. The ESR spectra of the DEPMPPOc–OOR spin adducts exhibit more straightforward patterns and are more easily assignable.