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

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journal contribution
posted on 02.04.2010, 00:00 by Jesus M. Aizpurua, Itxaso Azcune, Raluca M. Fratila, Eva Balentova, Maialen Sagartzazu-Aizpurua, Jose I. Miranda
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-butadiyne 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.