THE RELEASE OF SINGLET OXYGEN IN THE REACTION OF DIOXIRANES WITH AMINE N-OXIDES

The reactivity of dimethyldioxirane and methyl(trifluoromethyl)dioxira ne towards the amine N-oxides 1a-13a and ammonium derivatives 13b-d ha s been investigated. In the dioxirane oxidation of the tertiary amines and nitrogen heteroarenes, the expected N-oxides are not always forme d. Instead, the in situ generated N-oxides are deoxygenated by the dio xirane with the release of singlet oxygen (O-1(2)) at comparable or ev en higher rates than the amine oxidation. The amount of O-1(2) has bee n quantified by IR chemiluminescence and by chemical trapping with 9,1 0-dimethyl-anthracene. The nucleophilicity of the N-oxide determines t he efficacy of the O-1(2) release in the deoxygenation. Thus, for the less nucleophilic heteroaromatic N-oxides, the deoxygenation of the am ine oxide competes ineffectively with the oxidation of the amine. The ammonium derivatives 13b-d do not promote the decomposition of the dio xiranes; as expected, they are epoxidized.