Reaktion #3008

Reaktionsgleichung

toluene ethyl formate methanol

HCl

4-hydroxy-6-[2-(3,4-dihydroxyphenyl)-2-hydroxyethyl]-2H-pyran-2-one

4-Hydroxy-6-[2-(3,4-dihydroxyphenyl)-2-hydroxyethyl]-2H-pyran-2-one

tetrahydrofuran

→

6-[2-(3,4-Dihydroxyphenyl)vinyl]-4-hydroxy-2H-pyran-2-one

Lösungsmittel

formic acid

Reaktionsbedingungen

Aufarbeitung

1. 1
   TemperaturThe resulting clear solution was heated for 2-3 hours
2. 2
   Temperaturunder reflux until it
3. 3
   TrocknenAfter drying over sodium sulphate the solution
4. 4
   Sonstigewas strongly evaporated (residual volume ca. 50 ml) and it
5. 5
   Sonstigewas crystallized

Vorschrift

2 ml 3N HCl was added to a suspension of 8.0 g (30 mmol) 4-hydroxy-6-[2-(3,4-dihydroxyphenyl)-2-hydroxyethyl]-2H-pyran-2-one VII and 300 ml tetrahydrofuran. The resulting clear solution was heated for 2-3 hours under reflux until it was no longer possible to detect starting material. (TLC control, mobile solvent: toluene/ethyl formate/methanol 5:4:1, 0.5% formic acid). After drying over sodium sulphate the solution was strongly evaporated (residual volume ca. 50 ml) and it was crystallized by admixing with ether. Yield 4.7 g (63%) hispidine II, melting point 232°-234° C. (decomp.) or melting point 253° C. (decomp; bunch of needles from toluene/ethyl formate).

Quelle