Reactions of Nitroxides. Part XII [1]. – 2,2,6,6-Tetramethyl-1-oxyl- 4-piperidyl Chloroformate – A New Reactive Nitroxyl Radical. A One-pot Synthesis of 2,2,6,6-Tetramethyl-1-oxyl-4-piperidyl N,N-Dialkyl-carbamates

The reactive nitroxides 2,2,6,6-tetramethyl-1-oxyl-4-piperidyl chloroformate and 2,2,6,6-tetramethyl-1-oxyl-4-piperidyl chlorothionoformate were synthesized from 2,2,6,6-tetramethyl-4-hydroxypiperidin-1-oxyl and diphosgene (68%) or thiophosgene (61%), respectively. The reactions of the chloroformate and chlorothionoformate with lower secondary amines lead to 2,2,6,6-tetramethyl-1-oxyl-4-piperidyl N,N-dialkylcarbamates (59 – 94%) and thionocarbamates (35 – 65%), respectively. Unexpectedly, the same 2,2,6,6-tetramethyl-1-oxyl-4-piperidyl N,N-dialkylcarbamates were obtained directly in a one-pot reaction of 2,2,6,6-tetramethyl-4-hydroxypiperidin-1-oxyl with diphosgene and lower tertiary alkylamines by dealkylation in 32 – 86% yield. The antifungal activity of the synthesized carbamates and thionocarbamates has been demonstrated.