"Click" Synthesis of Nonsymmetrical Bis(1,2,3-triazoles)

Unsymmetrically 1,1'-disubstituted 4,4'-bis-1H-1,2,3-triazoles 4 have been prepared from 4-ethynyl-1,2,3-triazoles 5 and azides. Following a "double-click" strategy, two complementary approaches were implemented for the preparation of the key 4-ethynyltriazole intermediates 5: (a) the stepwise Swern oxidation/Ohira-Bestman alkynylation of readily available 4-hydroxymethyl-1,2,3-triazoles 8 and (b) the stepwise cycloaddition of TMS-1,4-butadlyne 9. The method is highlighted by its compatibility with orthogonally protected and functionalized saccharide-peptide hybrids and its ability to be extended to the trisubstituted counterparts 12.