The Nicholas reaction has been applied to the installation of alkyne ligation handles. Acid-promoted propargylation of hydroxyl, sulfhydryl, amino, and carboxyl groups using dicobalt hexacarbonyl-stabilized propargylium ions is reported. This method is useful for introduction of propargyl groups into base-sensitive molecules, thereby expanding the toolbox of methods for the incorporation of alkynes for bio-orthogonal reactions. High-value molecules are used as the limiting reagent, and various propargylium ion precursors are compared.
Bibliographical noteFunding Information:
We acknowledge the NIH (R21-CA194661 to D.A.H. and R01-GM054161 to K.M.B.) and the Department of Defense (PC141033 to D.A.H.) for funding. Mass spectrometry performed at the University of Minnesota was conducted at the Masonic Cancer Center Analytical Biochemistry Core Facility, which is supported by the National Institute of Health (P30-CA77598).