Generation of Alkoxyl Radicals from N-Alkoxy-2-pyridones

Abstract

Alkoxyl radicals have unique characteristic properties such as a facile β-fragmentation and a hydrogen abstraction due to their high reactivity. Various alkoxyl radical precursors are normally prepared from alcohols and include nitrites, nitrates, hypohalites, sulfenyl ethers, and Nalkoxyphthalimides. Especially, N-alkoxypyridine-2thiones 3 have attracted a great deal of attention as synthetically useful alkoxyl radical precursors. However, preparations of N-alkoxypyridine-2-thiones 3 are problematic due to competing Oand S-alkylation (eq. 1). Even under carefully controlled conditions, the desired product 3 is normally obtained in poor yields with a significant amount of undesired S-alkylated side product 4. In addition, the radical precursor is also unstable in light. Thus, some improved procedures have been reported, but the chemical yields were not very high. Since radical precursors are needed to be stable for safe handling and better chemical yields, we have been interested in N-alkoxy-2-pyridones 5 as new alkoxyl radical precursors.