Mechanistic Insights on Azide-Nitrile Cycloadditions: On the Dialkyltin Oxide-Trimethylsilyl Azide Route and a New Vilsmeier-Haack-Type Organocatalyst
David Cantillo, Bernhard Gutmann and C. Oliver Kappe*
*Christian Doppler Laboratory for Microwave Chemistry (CDLMC) and Institute of Chemistry, Karl-Franzens-University Graz, Heinrichstrasse 28, A-8010 Graz, Austria, Email: oliver.kappeuni-graz.at
D. Cantillo, B. Gutmann, C. O. Kappe, J. Am. Chem. Soc., 2011, 133, 4465-4475.
DOI: 10.1021/ja109700b (free Supporting Information)
An organocatalyst, 5-azido-1-methyl-3,4-dihydro-2H-pyrrolium azide, generated in situ from N-methyl-2-pyrrolidone (NMP), sodium azide, and trimethylsilyl chloride, enables the formation of tetrazoles by cycloaddition of sodium azide with organic nitriles under neutral conditions and microwave heating. The organocatalyst accelerates the azide-nitrile coupling by activating the nitrile substrate.
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Formation of organocatalyst followed by catalytic cycle