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Updated: Dec 25, 2025

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
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Synthesis of Bridged Azacycles and Propellanes via Nitrene/Alkyne Cascades
1Department of Chemistry, University of Houston, 3585 Cullen Boulevard, Fleming Building Room 112, Houston, Texas 77204-5003, United States.
Abstract:
A nitrene/alkyne cascade reaction terminating in C-H bond insertion to form functionalized bridged azacycles from carbonazidates is presented. Due to an initial Huisgen cyclization, all carbonazidates reacted with the alkyne in an exo mode in contrast to the use of sulfamate esters, which react predominately in an endo mode. Substrates with different ring sizes as well as different aryl and heteroaryl groups were also explored. Variation of the nitrene tether showed that 7-membered rings were the maximum ring size to be formed by nitrene attack on the alkyne. Examples incorporating stereocenters on the carbonazidate's tether induced diasteroselectivity in the formation of the bridged ring and two new stereocenters. Additionally, propellanes containing aminals, hemiaminals, and thioaminals formed from the bridged azacycles in the same reaction via an acid-promoted rearrangement.
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