The Direct Introduction of Carbonates α to Carbonyl Groups
Adrian Hall, Kerri L. Jones, Teyrnon C. Jones, Niall M. Killeen, Robert Pörzig, Paul H. Taylor, Sze Chak Yau, Nicholas C. O. Tomkinson*
*School of Chemistry, Main Building, Cardiff University, Park Place,
Cardiff, CF10 3AT, UK, Email: tomkinsonnc
cardiff.ac.uk
A. Hall, K. L. Jones, T. C. Jones, N. M. Killeen, R. Pörzig, P. H. Taylor, S. C. Yau, N. C. O. Tomkinson, Synlett, 2006, 3435-3438.
DOI: 10.1055/s-2006-956473
Abstract
Bench stable N-Methyl-O-alkoxyformate hydroxylamine hydrochloride reagents can be prepared in two high-yielding steps from N-Boc-N-methyl hydroxylamine. Subsequent reaction with various carbonyl compounds give the corresponding α-functionalised products in good yield via a proposed [3,3]-sigmatropic rearrangement.
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Details
The document describes a novel method for the direct formation of a-oxycarbonates from aldehydes and ketones. The process utilizes N-methyl-O-alkoxyformate hydroxylamine hydrochloride reagents, which are prepared in two high-yielding steps from N-Boc-N-methyl hydroxylamine. These reagents are bench-stable and react with various carbonyl compounds to produce α-functionalized products in 48-98% yields via a [3,3] sigmatropic rearrangement. The method is advantageous as it avoids the use of metals and sensitive intermediates, and it proceeds under mild conditions in the presence of moisture and air. The reagents are easily prepared and stable, making the process practical and efficient. The reaction is ineffective for primary centers, allowing for complete regiospecificity in non-symmetrical substrates. Additionally, the phenyl carbonate reagent can lead to either a 4,5-disubstituted-4-oxazolin-2-one framework or an a-functionalized carbonyl compound depending on the reaction conditions. This method provides a significant extension to the chemistry accessible from N,O-disubstituted hydroxylamine reagents and is currently being developed for asymmetric processes.
Key Words
metal-free synthesis, hydroxylamines, carbonates, α-hydroxylation
ID: J60-Y2006-4830
