[332-77-4] · C6H10O3 · 2,5-Dihydro-2,5-dimethoxyfuran · (MW 130.14)
(masked 1,4-dialdehyde; convenient for the synthesis of substituted furans and tetrahydrofurans)
Physical Data: colorless liquid; bp 160-162 °C; d 1.0730 g cm-3.
Solubility: practically insol H2O; sol MeOH, Et2O, THF.
Form Supplied in: commercially available as a mixture of cis and trans isomers.
Preparative Method: electrolytic methoxylation of Furan.1
Handling, Storage, and Precautions: flammable liquid; must be stored in a cool, ventilated place. Noxious by inhalation, ingestion, or contact with skin. Use in a fume hood.
2,5-Dihydro-2,5-dimethoxyfuran (1) reacts with 1,3-dicarbonyl compounds in the presence of Lewis acids to give 2-substituted furans after elimination of MeOH (eq 1).2
In the same manner, Chlorodiphenylphosphine affords furan-2-phosphine oxide,3 in contrast to Cyanotrimethylsilane which leads to 2-cyano-5-methoxydihydrofuran.4
Photocycloadditions of (1) to anisole,5 triazolo[4,3-b]pyridazine,6 or Maleic Anhydride7 give 2,3,4,5-tetrasubstituted furans. 1,3-Dipolar cycloaddition can be performed with nitrones8 and nitrile oxides.9 The thermal [4 + 2] reaction between (1) and Cyclopentadiene proceeds in good yield.10 Permanganate oxidation of the isomer mixture of (1) affords exclusively the diol from the cis isomer (eq 2).11
Ozonolysis of (1) followed by reduction leads to a monoprotected glyoxal useful for reactions with stabilized phosphoranes (eq 3).12
g-Aldehydo esters are obtained from (1) by double bond migration mediated by a ruthenium hydride complex (eq 4),13 or by treatment with Iodotrimethylsilane (in lower yield).14
Université René Descartes, Paris, France
CNRS, Gif-sur-Yvette, France