Conversion of Unprotected Aldose Sugars to Polyhydroxyalkyl and <i>C</i>-Glycosyl Furans via Zirconium Catalysis
作者:Nima Ronaghi、David M. Fialho、Christopher W. Jones、Stefan France
DOI:10.1021/acs.joc.0c02176
日期:2020.12.4
An efficient, zirconium-catalyzed conversion of unprotected aldose sugars with acetylacetone to polyhydroxyalkyl furans or C-glycosylfurans is reported. The furan products are formed in up to 93% yield using 5–10 mol % ZrCl4. Pentoses are readily converted at room temperature, while hexoses and their oligosaccharides require mild heating (i.e., 50 °C). Efficient conversions of glycolaldehyde, glyceraldehyde
Furylhydroperoxides are accessible by three different methodologies. In the enzymatic approach, lypoxygenase is employed on non lipid-like substrates. Transitionmetalcatalyzedepoxidation of allylic alcohols is strongly dependent on the structure of the involved hydroperoxide.
PhI(OCOCF3)(2) (PIFA) in the presence of trifluoroacetic acid (TFA) in CH2Cl2 efficiently promotes the oxidative cycloisomerization of 2-propargyl 1,3-dicarbonyl compounds to give 4,5-disubstituted furfuryl alcohols. PIFA in hexafluoroisopropanol (HFIP) or PIFA-BF3 center dot OEt\(2) in CH2Cl2 bring about the direct formation of furfurals from 2-propargyl 1,3-dicarbonyl compounds. In a few cases, PhI=O is suitable for the direct formation of furfurals. (C) 2011 Elsevier Ltd. All rights reserved.