Scientific Article
previous document  unige:7852  next document
add to browser collection
Title

Hypervalent Iodine Chemistry: New Oxidation Reactions Using the Iodosylbenzene-Trimethylsilyl Azide Reagent Combination. Direct α- and ß-Azido Functionalization of Triisopropylsilyl Enol Ethers

Authors
Magnus, Philip
Evans, P. Andrew
Roe, Michael B.
Hulme, Christopher
Published in Journal of the American Chemical Society. 1996, vol. 118, no. 14, p. 3406-3418
Abstract Treatment of triisopropylsilyl (TIPS) enol ethers with PhIO/TMSN3/at -18 to -15 °C rapidly (5 min) gave ß-azido TIPS enol ethers in high yields, with only traces of the a-azido adduct. The reaction is very sensitive to temperature changes, with the a-pathway being favored at -78 °C and the ß-pathway at -15 to -20 °C. Addition of catalytic amounts of the stable radical TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl) significantly reduced the ß-azidonation and increased the a-azidonation reaction. A mechanistic hypothesis is presented that offers a clear distinction between the a- and ß-functionalization pathways. The key difference between the two reactions is that the a-pathway is an azide radical addition process and the ß-pathway involves ionic dehydrogenation. Efforts to extend the unusual ß-functionalization reaction to other trimethylsilyl derivatives (TMSX) were unsuccessful. The reagent combination PhIO/TMSN3 is the only system we have found that results in clean, high-yield ß-functionalization. Attempts to substitute iodine with S, Se, P, As, or Te did not result in an active oxidant, although in the case of diphenyltelluroxide we were able to isolate the stable crystalline adduct bis[azidodiphenyltellurium(IV)] oxide.
Identifiers
Full text
Article - document accessible for UNIGE members only Limited access to UNIGE
Citation
(ISO format)
MAGNUS, Philip et al. Hypervalent Iodine Chemistry: New Oxidation Reactions Using the Iodosylbenzene-Trimethylsilyl Azide Reagent Combination. Direct α- and ß-Azido Functionalization of Triisopropylsilyl Enol Ethers. In: Journal of the American Chemical Society, 1996, vol. 118, n° 14, p. 3406-3418. https://archive-ouverte.unige.ch/unige:7852

462 hits

3 downloads

Update

Deposited on : 2010-06-21

Export document
Format :
Citation style :