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

• Published in: Russian chemical bulletin Vol. 73; no. 5; pp. 1460 - 1464
• Main Authors: Medved’ko, A. V., Ermakov, M. O., Vatsadze, S. Z.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.05.2024; Springer Nature B.V
• Subjects: Brief Communications; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Crystal structure; Free radicals; Inorganic Chemistry; Ketones; Mass spectrometry; Molecular structure; Organic Chemistry; Reagents; 2,2,6,6-tetramethylpiperidine-1-oxyl; the Mannich reaction; ESR spectroscopy; free radicals; bispidine; X-ray diffraction analysis
• ISSN: 1066-5285; 1573-9171
• DOI: 10.1007/s11172-024-4266-y

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.