PhI(OAc)<sub>2</sub>-Promoted Rearrangement of the Hydroxyl Group: Ring Expansion of 4-Hydroxy-2-cyclobutenone to 2(5<i>H</i>)-Furanone in Comparison with Ring Cleavage of the α-Hydroxycycloalkanone to the ω-Formyl Ester
作者:Masatomi Ohno、Isamu Oguri、Shoji Eguchi
DOI:10.1021/jo990704v
日期:1999.12.1
Reaction of 4-hydroxy-2-cyclobutenones with PhI(OAc)(2) in 1,2-dichloroethane at reflux temperature gave rise to 5-acetoxy-2(5H)-furanones as a rearranged product, formation of which is explained by ring cleavage of the once formed hypervalent iodine intermediate and following recyclization of the resulting acyl cation with a carbonyl oxygen. Likewise, 5-methoxy-2(5H)-furanones were obtained in better yields by using methanol as both a solvent and a nucleophile. Extension of this reaction to simple 2-hydroxycycloalkanones resulted in ring cleavage to methyl omega-formylalkanoates under milder conditions. In this case, the mechanism is explained by known glycol cleavage with PhI(OAc)(2).