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. 2007 Oct 17;104(43):16793–16797. doi: 10.1073/pnas.0707090104

Fig. 1.

Fig. 1.

Design and synthesis of Cu-free click chemistry reagents. (A) The copper-catalyzed azide–alkyne cycloaddition. (B) The Cu-free click reaction of azides and DIFOs. (C) (i) Sodium hydride, allyl bromide, 52%. (ii) Pyridinium chlorochromate, 91%. (iii) Lithium hexamethyldisilazide (LHMDS), chlorotriethylsilane (TESCl), 91%. (iv) Selectfluor, 95%. (v–vii). Cat. LHMDS, 95%. (viii) Potassium hexamethyldisilazide (KHMDS), TESCl, 97%. (ix) Selectfluor, 74%. (x) Cat. RuCl3, NaIO4, 96%. (xi) KHMDS, N-phenylbis(trifluoromethanesulfonamide), 46%. (xii) Lithium diisopropylamide, 11%. (D) Derivatives of DIFO and a linear alkyne (alk) containing Alexa Fluor 488, Alexa Fluor 568, or biotin.