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Exit Seminar: "1,2-Diamination of alkenes via reduction of 1,2,3-triazolinium ions"

Speaker(s) / Presenter(s):
Setareh Saryazdi

Graduate Student Profile

Abstract: 1,2-diamine substructures are prevalent functional motifs found in natural products, pharmaceutical compounds, and ligands. The interesting utilities of 1,2-diamines have inspired many synthetic chemists to design various methodologies for the preparation of these structures from simple precursors such as alkenes. Despite the well-established analogous dihydroxylation or aminohydroxylation of alkenes, the introduction of two amino groups across the double bond has been more challenging to accomplish. In this work, we described two different, but related methods using simple and easily accessible reagents for 1,2-diamination of alkenes. In the first method, an alkene undergoes 1,3-dipolar cycloaddition with an organic azide to form a 1,2,3-triazoline. Subsequent N-alkylation of the generated 1,2,3-triazoline gives the 1,2,3-triazolinium ion, which was then hydrogenated over Raney Ni with a balloon of H2 to produce 1,2-dimine. Traditionally, it has been believed that a 1,2,3-triazoline is an unstable species in the presence of heat or light and will readily extrude N2 to form an imine or an aziridine.  However, most of the 1,2,3-triazolines prepared in this work were stable to the extrusion of N2 at the temperature required for their formation. In the second method, the alkene undergoes 1,3-dipolar cycloaddition with a 1,3-diaza-2-azoniaallene (azidium ion) to afford a 1,2,3-triazolinium ion directly. The 1,2,3-triazolinium ions are reduced to the corresponding 1,2-diamines using the same conditions described above. X-ray crystallographic analysis and 1D/2D NMR spectra confirmed the stereochemistry of the synthesized 1,2,3-triazolinium ions and 1,2-diamines.

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