- 1,3-Dipolar cycloadditions of MeOPEG-bounded azides
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1,3-Dipolar cycloadditions of MeOPEG-supported azide 2 with a variety of dipolarophiles have been studied. 1-MeOPEG-supported 1,2,3-triazoles 4 and 5, 1,2,3,4-tetrazoles 12 and aziridine 14 were obtained in nearly quantitative yields. The removal of the MeOPEG moiety from the 1,2,3-triazole nucleus was achieved by acidic cleavage of the cycloadduct mixtures 4 and 5 giving 4- and 5-substituted-1,2,3-triazoles 6 and 7.
- Molteni, Giorgio,Del Buttero, Paola
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- Synthesis of N-unsubstituted 1,2,3-triazoles via a cascade including propargyl azides, allenyl azides, and triazafulvenes
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About thirty NH-1,2,3-triazoles with at least one additional functional group in a side chain at C-4 were prepared from propargyl substrates. These reactions included propargyl azides and their [3,3]-sigmatropic rearrangement to generate short-lived allenyl azides, which cyclized to form triazafulvenes that could be trapped by addition of N- or O-nucleophiles. In most cases, simple substrates and cheap sodium azide were utilized as starting compounds, and the syntheses were performed by using a one-pot procedure without isolation of any dangerous azides. This method to prepare NH-1,2,3-triazoles turned out to be compatible with quite different substitution patterns of the propargyl substrate.
- Banert, Klaus,Hagedorn, Manfred,Hemeltjen, Claudia,Ihle, Andreas,Weigand, Kevin,Priebe, Hanno
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p. 338 - 361
(2016/11/21)
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- Reactions of Unsaturated Azides, 6 Synthesis of 1,2,3-Triazoles from Propargyl Azides by Rearrangement of the Azido Group. - Indication of Short-Lived Allenyl Azides and Triazafulvenes
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Treatment of 3-bromo-3-methyl-1-butyne (1) or 1-iodo-3-methyl-1,2-butadiene (3) with solutions of sodium azide affords 3-azido-3-methyl-1-butyne (5) which reacts already at room temperature to 1,2,3-triazoles 8-11.Structures of 5 and 8-11 are verified by independent syntheses and spectroscopic data although in part other assignments of structures have been published.The preparation of 1H-1,2,3-triazoles via propargyl azides is carried out in the presence of various nucleophiles and investigated by means of 15N-labelled starting material as well as optically active 3-azido-1-butyne (R-21).The only mechanism compatible with all results includes short-lived allenyl azides and triazafulvenes.Thus, propargyl azide 14 rearranges to allenyl azide 16 leading to triazafulvene 18 by rapid ring closure.Finally, 18 is trapped by nucleophiles to give triazole 17.The conversion of various propargyl compounds into N-unsubstituted 1H-1,2,3-triazoles 23, 41, 44, 46, 50, and 51 is effected by a one-pot procedure without isolation of 14 and turns out to be a convenient method to prepare these heterocycles. - Key Words: Allenyl azides, ring closure of / Propargyl azides, rearrangement of / Triazafulvenes, nucleophilic addition to / Triazoles, preparation of
- Banert, Klaus
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p. 911 - 918
(2007/10/02)
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