Treatment of 3-bromo-3-methyl-I-butyne (1) or 1 4odo-3-methyl-13-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-tn'azoles 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 1 H-1,2,3-triazoles via propargyl azides is carried out in the presence of various nucleophiles and investigated by means of "N-labelled starting material as well as optically active 3-azido-I-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 lH-1,2,3-triazoles 23,41,44,46, 50, and 51 is &&ed by a one-pot procedure without isolation of 14 and turns out to be a convenient method to prepare these heterocycles.Vinyl azides which are known for their manifold reactions can be synthesized by various methods". But all attempts to isolate allenyl azides -possible precursors for yet unknown alkylideneazirines -were unsu~cessful~~~). In a publication by Shiner and Humphrey, the authors claimed to have obtained the allenyl azide 4 together with the propargyl azide 5 from the reaction of bromides 1 or 2 with sodium azide in deuterated aqueous ethanol'). However, 4 and 5 were only characterized in the reaction mixture by their 'H-NMR data, because they decomposed already at room temperature to unknown products. Since the observation of 4 represents the only direct reference to an allenyl azide, detailed reinvestigations of the reaction of 1 with sodium azide in aqueous alcohols are now presented.
1,2,3-Triazoles from 3-Azido-3-methyl-1-butyne (5)Treatment of 1 6.7) with sodium azide in aqueous ethanol at first gives only the propargyl azide 5, which subsequently produces the triazoles 8 -los, along with the other solvolysis products, 2-methyl-l-buten-3-yne, 2-methyl-3-butyn-2-01, and 12. NMR data indicate that 9 was taken for 3 in the literature, that 5 was correctly recognized, and that 8 and 10 are the succeeding products not identified by Shiner and Humphrey'). If the reaction is carried out using deuterated solvents the allenyl azide 4 cannot be detected by 'H-NMR spectroscopy. With sodium azide in aqueous methanol, 1 or the less reactive 37.'0' similarly furnish 5 and subsequently 8, 9, and 11. Due to the formation of several solvolysis products'the triazoles are isolated in low yields (16% of 9 and 16% of 11 based on 1). Using sodium azide in aqueous acetone affords only 8 and 9 as final triazoles (43% yield based on 1). Although the azide 5 is very unstable at room temperature it can be isolated from 3 and hexadecyltributylphosphonium azide (QN3) * I ) in 44% yield. With sodium azide in aqueous alcohols, 5 produces 8 and 9 as well as 10 or 1...
