Mild Oxidative One-Pot Allyl Group Cleavage
Pavel I. Kitov and David R. Bundle*
*Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
T6G 2G2, Email: dave.bundle
ualberta.ca
P. I. Kitov, D. R. Bundle, Org. Lett., 2001, 3, 2835-2838.
DOI: 10.1021/ol016278t
Abstract
A new one-pot method is described for the removal of O- and N-allyl protecting groups under oxidative conditions at near neutral pH. The allyl group undergoes hydroxylation and subsequent periodate scission of the vicinal diol. Repetition of this reaction sequence on the enol tautomer of the aldehyde intermediate releases the deprotected functional group.
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proposed mechanism
Details
The document describes a new one-pot method for the removal of O- and N-allyl protecting groups under oxidative conditions at near-neutral pH. The process involves hydroxylation of the allyl group, followed by periodate scission of the resulting vicinal diol, and further oxidation of the enolic form of the aldehyde intermediate. This method is advantageous over traditional two-step procedures, which often require isomerization and subsequent acid hydrolysis or oxidation. The optimized reaction conditions involve using osmium tetroxide with 4-methylmorpholine N-oxide and sodium periodate in a dioxane-water mixture. The reaction yields a high purity product, with the best results obtained at room temperature over 4-5 days. The method is compatible with a wide range of common O- and N-protective groups and does not affect benzyl ethers. The presence of water is crucial for the catalytic cycle and regeneration of OsO4. The addition of a secondary amine, such as piperidine, can significantly accelerate the reaction. This new method is particularly useful for selective deprotection in complex synthetic schemes and can be applied to both solution and solid-phase supports. The research was supported by the Canadian Bacterial Disease Network (CBDN).
Key Words
Allyl Ethers, Deprotection (Amines, Alcohols), Osmium tetroxide, NMO, Sodium periodate
ID: J54-Y2004-720
