Sciencemadness Discussion Board

Furfurylidene acetone

Boffis - 16-3-2025 at 12:01

Has anyone any experience of the reaction of acetone and furfuraldehyde? I tried to produce furfurylideneacetone today by mixing a little freshly distilled crude furfural with a 3 molar excess of acetone and adding dilute sodium hydroxide in methanol-water mixture (to improve miscibility) to the room temperature mixture. Before I had even added a tenth of the caustic solution the mixture became so hot that the acetone began to boil off and the mixture became very hot and dark brown. On cooling no solid product formed only a brown, water immiscible liquid.

Clearly furfural is much more reactive than benzaldehyde but the sudden heating seams to destroy the furfural.

Does anyone have a ref to a preparation? or have any proctical experience?

DraconicAcid - 16-3-2025 at 12:13

I haven't tried that exact reaction, but keeping the reaction mixture cold is recommended for all the aldol condensations I've tried. It works nicely with benzaldehyde, p-anisaldehyde, and cuminaldehyde.

bnull - 16-3-2025 at 13:22

Try solid Ca(OH)2 or Mg(OH)2, or even MgO, in place of sodium hydroxide.

Dr.Bob - 16-3-2025 at 18:33

Try adding the furfural slower or dropwise. As well as cooling the reaction.

clearly_not_atara - 17-3-2025 at 19:18

Quote:
Has anyone any experience of the reaction of acetone and furfuraldehyde? I tried to produce furfurylideneacetone today by mixing a little freshly distilled crude furfural with a 3 molar excess of acetone and adding dilute sodium hydroxide in methanol-water mixture (to improve miscibility) to the room temperature mixture. Before I had even added a tenth of the caustic solution the mixture became so hot that the acetone began to boil off and the mixture became very hot and dark brown. On cooling no solid product formed only a brown, water immiscible liquid.

IIRC furfural forms more stable imines than benzaldehyde. I think this means that the furan ring is more electron-withdrawing than a benzene ring. That would account for a higher rxn temperature.

I think the usual trick here would be to add more of an inert solvent, like acetonitrile, THF, dioxolane, DMF, EtOAc (may react with NaOH unfortunately) to keep the reaction cool. Unfortunately it probably has to be aprotic and not acetone, and it's better if it's polar.

DraconicAcid - 17-3-2025 at 20:00

Quote: Originally posted by clearly_not_atara  
Quote:
Has anyone any experience of the reaction of acetone and furfuraldehyde? I tried to produce furfurylideneacetone today by mixing a little freshly distilled crude furfural with a 3 molar excess of acetone and adding dilute sodium hydroxide in methanol-water mixture (to improve miscibility) to the room temperature mixture. Before I had even added a tenth of the caustic solution the mixture became so hot that the acetone began to boil off and the mixture became very hot and dark brown. On cooling no solid product formed only a brown, water immiscible liquid.

IIRC furfural forms more stable imines than benzaldehyde. I think this means that the furan ring is more electron-withdrawing than a benzene ring. That would account for a higher rxn temperature.

I think the usual trick here would be to add more of an inert solvent, like acetonitrile, THF, dioxolane, DMF, EtOAc (may react with NaOH unfortunately) to keep the reaction cool. Unfortunately it probably has to be aprotic and not acetone, and it's better if it's polar.


Ethanol is a suitable solvent for this reaction, surely.

clearly_not_atara - 18-3-2025 at 13:11

^I was concerned about conjugate addition of the alkoxide to the alkene. But come to think of it isopropanol will not be deprotonated by NaOH.

Boffis - 23-3-2025 at 15:13

Two more "failed" attempts to produce furfurylidene acetone with different conditions /alkalis also resulted in a deep brownish yellow oil so I went back to the original paper Claisen & Ponder, J.L. Annalen d. Chem., 1884, pp137-148.

Funny isn't how a little time in the library can save hours of frustration! Apparently the desired compound melts at 37-38 C even after vacuum distillation and separates initially as a liquid. So it would appear that the reaction did infact work but I was expecting a solid product. Bugger!