The first example of the use of 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl in the Mannich reaction to obtain radical-labeled bispidines

Bispidine containing a paramagnetic group was obtained for the first time by the Mannich reaction using the 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO) free radical as a reagent. The structure of the target compound, tert-butyl 9-oxo-7-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-3,7-diazabicyclo[3.3.1]nonane-3-carboxylate, was confirmed by mass spectrometry and ESR spectroscopy, the molecular and crystal structure was established by X-ray diffraction analysis. In the synthesis of the starting 4-amino-TEMPO by the reductive amination reaction, the by-product of the further reaction of 4-amino-TEMPO with the starting ketone, the free biradical N-(2,2,6,6-tetramethyl-1-oxylpiperidin-4-yl)-2,2,6,6-tetramethyl-4-aminopiperidine-1-oxyl, was isolated and structurally characterized.