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Updated: Jun 6, 2025

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
4-Azaspiro[2.3]hexane, an Overlooked Piperidine Isostere: Multigram Synthesis and Physicochemical and Structural
Sergiy Galavskyy1,2, Anton Chernykh1,3, Oleksandr Liashuk1,2
1Enamine Ltd., Winston Churchill Street 78, Kyïv 02094, Ukraine.
Abstract:
An expedient approach to the synthesis of 4-azaspiro[2.3]hexane derivatives is described. The synthetic scheme consists of Tebbe olefination of N-Boc-protected 2-azetidinone (including the first use of the deuterated Petasis reagent Cp2Ti(CD3)2 in the building block preparation) and cyclopropanation of the resulting intermediate. The developed protocols allowed for the preparation of target building blocks on a multigram scale (up to 52 g). To illustrate the potential of the obtained 4-azaspiro[2.3]hexane derivatives for isosteric replacements in drug discovery, their physicochemical and structural characterization was performed, i.e., basicity (pKa) and lipophilicity (Log P) measurements, X-ray diffraction studies, and exit vector plot (EVP) analysis.
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