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Updated: Mar 1, 2026

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
Enantioselective Synthesis of Tetrahydropyridines/Piperidines via Stepwise [4 + 2]/[2 + 2] Cyclizations
Zhen Wang1, Huacheng Xu1, Qin Su1
1School of Pharmaceutical Sciences and Innovative Drug Research Centre, Chongqing University , Chongqing 401331, P.R. China.
Abstract:
A phosphine-catalyzed novel enantioselective [4 + 2]-annulation reaction between allene ketones and 1-azadienes has been developed, and tetrahydropyridines were obtained in good yields and with excellent enantioselectivities. Subsequent exposure of tetrahydropyridines to benzyne leads to a [2 + 2]-cyclization, creating optically enriched polycyclic piperidines with a quaternary stereogenic center and a cyclobutene moiety. The reported stepwise [4 + 2]/[2 + 2]-cycloadditions represent a new approach to access enantiomerically enriched nitrogen-containing six-membered ring systems.
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