Mingdi Yan Colloquium

Prof. Mingdi Yan from UMass Lowell will present a seminar as part of BU Chemistry's Colloquium series.

Title Electrophilic Azides: Unique Reactions for Materials Synthesis and Chemical Biology

Abstract: Organic azides are involved in rich transformations, including the nitrene chemistry through the release of nitrogen gas, reaction with nucleophiles and electrophiles, and cycloaddition with dipolarophiles. We have developed conjugation reactions using perfluoroaryl azides (PFAAs) as highly reactive nitrene precursors and electrophilic azides. Perfluorination significantly increases the stability of aryl azides than acyl, sulfonyl or alkyl azides, and facilitates the product characterizations by techniques such as 19F NMR and XPS. Fluorination increases the lifetime of the singlet nitrene, leading to the formation of C-H insertion and C=C addition products in high yields. Perfluorination also lowers the LUMO of the aryl azides, facilitating the reactions with electron-rich dipolarophiles such as enamines and enolates to give products that are impossible to obtain from non-fluorinated counterparts. Similarly, the PPAA-Staudinger reaction occurs at room temperature without the use of any catalysts at a rate of 10 (to the 4th) times faster than the classic Staudinger ligation and gives stable phosphoimines in high yields. This talk will highlight the applications of these reactions in materials synthesis, such as the synthesis of glyconanomaterials for targeted antibiotic delivery to bacteria and functionalization of graphene, including using substrates to modulate the reactivity of graphene. Examples will be given on using bacterium-specific sugars to construct chemical probes to image cells and bacteria by hijacking the carbohydrate transport pathways.