Reaction #1153144

Reaction equation

hydrochloric acid

H2SO4

NaCl

3,4-dihydroxyacetophenone

2,4-dihydroxybenzaldehyde

→

3′,4′,7-trihydroxyflavylium chloride

Yield 75.0%

Solvents

ethyl acetate

Conditions

Workup

1. 1
   Otherwas bubbled in a two-necked flask
2. 2
   Otherto precipitate after 30 minutes
3. 3
   workup.WAITThe solution was kept at −18° C. for 3 days
4. 4
   Filtrationit was filtered
5. 5
   OtherThe filtrate was evaporated
6. 6
   Otherthe product precipitated
7. 7
   OtherIt was separated from the ether
8. 8
   workup.DISSOLUTIONdissolved in hot methanol
9. 9
   workup.ADDITIONit was added slowly to an equivalent volume of acetone
10. 10
    Otherto precipitate
11. 11
    FiltrationAfter filtration
12. 12
    Otherthe filtrate was evaporated
13. 13
    workup.DISSOLUTIONdissolved in a minimum of methanol
14. 14
    workup.ADDITIONether was added until a precipitate

Procedure

At 0° C., hydrochloric acid (generated by dropwise addition of H2SO4 to NaCl) was bubbled in a two-necked flask containing 12 g (0.079 mol) of 3,4-dihydroxyacetophenone, 10.88 g (0.079 mol) of 2,4-dihydroxybenzaldehyde and 100 ml of ethyl acetate distilled beforehand. The product started to precipitate after 30 minutes. The bubbling was continued for another 1 hour and then the reaction was stopped. The solution was kept at −18° C. for 3 days and then it was filtered. The filtrate was evaporated and it was taken up in ether; the product precipitated. It was separated from the ether, dissolved in hot methanol and then it was added slowly to an equivalent volume of acetone. The solution was placed in a refrigerator and the product started to precipitate. After filtration, the filtrate was evaporated, dissolved in a minimum of methanol and then ether was added until a precipitate appeared. The procedure was thus repeated several times until precipitate no longer appeared. The purity of the 3′,4′,7-trihydroxyflavylium chloride precipitate thus obtained with a yield of 75% was checked by HPLC (high-performance liquid chromatography).

Source