Synthesis, Characterization and Reactions of (Azidoethynyl)trimethylsilane

Abstract

Synthesis of azido(trimethylsilyl)acetylene (6) was performed by treating the iodonium salt 5 with highly soluble hexadecyltributylphosphonium azide (QN 3 ) at´40˝C. Although this product is very unstable, it can nevertheless be trapped by the click reaction with cyclooctyne to give the corresponding 1,2,3-triazole, and also directly characterized by 1 H-and 13 C-NMR data as well as IR-spectra, which were measured in solution at low temperature and in the gas phase. The thermal or photochemical decay of azide 6 leads to cyano(trimethylsilyl)carbene. This is demonstrated not only by quantum chemical calculations, but also by the trapping reactions with the help of isobutene.

The Chemistry of Unusually Functionalized Azides

“…When the analogous reaction of the iodonium salt 13c with QN 3 in deuterated chloroform at -40 °C was monitored by 1 H NMR spectroscopy, nearly quantitative formation of the azide 4c was observed. 24 Thus, it was not surprising that the trapping product 9c was isolated in high yield (89%) after treating the reaction mixture with cyclooctyne. After recondensation of the reaction mixture with 4c, however, 1 H NMR analysis showed a reduced yield of only 10-54%, even when the recondensation was performed at -40 °C with the help of an oil diffusion pump (10 -6 Torr).…”

“…26 Ethynyl azide (4a) decomposed with a half-life period of approximately 17 hours in deuterated dichloromethane at -30 °C, whereas the half-life periods of 4c in deuterated chloroform turned out to be 230 min at -30 °C and 35 min at -20 °C. 19,24 The decay of 4a in chlorinated solvents such as chloroform or dichloromethane and in the absence of reactive partners led to C-Cl insertion products via the carbene intermediate 10a. 26 In spite of their properties as short-lived compounds, ethynyl azides 4 can be reacted intermolecularly, for instance, with cyclooctyne to afford 18a (35% yield based on precursor 13a) or 18c (95% yield based on 4c).…”

“…Treatment of 13a or 13c with QN 3 in the high-boilingpoint polar solvent propylene carbonate at -35 °C or -30 °C, respectively, enabled the transport of the volatile products 4a or 4c into the gas phase by using a vacuum line and cold traps. 24,26,27 Thus, gas phase IR spectra of 4a and 4c were measured to study the decay of the ethynyl azides. These investigations confirmed that 4a is more stable than 4c, not only in solution, but also in the gas phase, which is in agreement with previous quantum chemical calculations.…”

“…In situ formation of substituted azidoacetylenes has recently been utilized to prepare a variety of products via decomposition to the corresponding cyanocarbenes and the inter-or intramolecular trapping reactions of these carbenes. 11,19,24,26,29…”

Differentiation between Enamines and Tautomerizable Imines Oxidation Reaction Mechanism using Electron-Vibration-Vibration Two Dimensional Infrared Spectroscopy

“…Since the intermediates are highly reactive and have short lifetimes, it is difficult, in general, to isolate and investigate them. The techniques commonly employed for this purpose include UV/Vis [ 1 , 2 ], infrared (IR) [ 3 , 4 , 5 , 6 , 7 ], electron paramagnetic resonance (EPR) [ 8 , 9 , 10 , 11 ] as well as nuclear magnetic resonance (NMR) spectroscopy [ 12 , 13 ]. Among these techniques, infrared (IR) spectroscopy is one of the most convenient tools.…”