In Situ Generation of the Ohira-Bestmann Reagent from Stable Sulfonyl Azide: Scalable Synthesis of Alkynes from Aldehydes
Tue Heesgaard Jepsen and Jesper Langgaard Kristensen*
*Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark, Email: jesper.kristensensund.ku.dk
T. H. Jepsen, J. L. Kristensen, J. Org. Chem., 2014, 79, 9423-9426.
The use of the recently reported bench-stable imidazole-1-sulfonyl azide as diazotransfer reagent enables an improved method for the in situ generation of the Ohira-Bestmann reagent. This method represents a scalable and convenient approach for the transformation of aldehydes into terminal alkynes and offers an easier workup compared to the existing in situ protocol due to increased aqueous solubility of waste products.
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Safety concerns have been raised about the synthesis and storage of imidazole-1-sulfonyl azide hydrochloride following an explosion during the preparation of this salt. [Org. Lett. 2011, 13, 2514, DOI: 10.1021/ol2007555] Further work has revealed that the hydrogensulfate and tetrafluoroborate salts are safe to synthesise, store and handle. [J. Org. Chem. 2012, 77, 1760-1764, doi: 10.1021/jo202264r].
E. D. Goddard-Borger, April 27, 2016