[Neel]

Hi, I tried the following reaction, but I only see starting material even after 6 hours. When I leave it overnight, compound degraded.

I would highly appreciate if you have any suggestions to make the product.

[sjb]

Hi, I tried the following reaction, but I only see starting material even after 6 hours. When I leave it overnight, compound degraded.

I would highly appreciate if you have any suggestions to make the product.

Could you not make it from serine? Protect the nitrogen, esterify, oxidize the alcohol, methylenate, reduce?

What happens when you reduce the temperature? No reaction at all?

[Honclbrif]

There could easily be a mass transport issue. How much CaCO₃ are you using, and how finely powdered is it? Since the carbonate isn't soluble in your solvent, you're really only reacting on the surface of the particles, so you've got to stack the deck in your favor as much as you can. With that in mind, why not use use a phase transfer catalyst like TBAB, or K₂CO3 and 18-crown-6?

You may also be able to do it with a selenoxide elimination instead.

[Neel]

Hi, I tried the following reaction, but I only see starting material even after 6 hours. When I leave it overnight, compound degraded.

I would highly appreciate if you have any suggestions to make the product.

Could you not make it from serine? Protect the nitrogen, esterify, oxidize the alcohol, methylenate, reduce?

What happens when you reduce the temperature? No reaction at all?

I tried the rxn at 150 C - still no rxn.

I have already done 3 steps, So would like to get this rxn going before thinking of alternate routes.

Thanks.

[Neel]

There could easily be a mass transport issue. How much CaCO₃ are you using, and how finely powdered is it? Since the carbonate isn't soluble in your solvent, you're really only reacting on the surface of the particles, so you've got to stack the deck in your favor as much as you can. With that in mind, why not use use a phase transfer catalyst like TBAB, or K₂CO3 and 18-crown-6?

You may also be able to do it with a selenoxide elimination instead.

I am using 2 molar eq. of a finely powdered CaCO3.

I will try TBAB.

Thanks.

[Honclbrif]

If you're sticking with the calcium carbonate, I'd up it to more like 10 equivalents. Its cheap and should be relatively easy to separate by filtration there shouldn't be a big issue with using a large excess.

[Dan]

I can't see your scheme, but if you need a more soluble carbonate, try Cs₂CO₃ - it has slight solubility in organic solvents, dramatically reduces reaction times in comparison to, say, K₂CO₃ and without a massive molar excess.

I'm doing a lot of sulfinate eliminations at the moment, and 10 eq K₂CO₃ in THF at reflux takes 8-16 hours, whereas 2.5 eq  Cs₂CO₃ in refluxing THF takes 30-60 min.

[Neel]

If you're sticking with the calcium carbonate, I'd up it to more like 10 equivalents. Its cheap and should be relatively easy to separate by filtration there shouldn't be a big issue with using a large excess.

Thanks. I'll try.

[Neel]

I can't see your scheme, but if you need a more soluble carbonate, try Cs₂CO₃ - it has slight solubility in organic solvents, dramatically reduces reaction times in comparison to, say, K₂CO₃ and without a massive molar excess.

I'm doing a lot of sulfinate eliminations at the moment, and 10 eq K₂CO₃ in THF at reflux takes 8-16 hours, whereas 2.5 eq  Cs₂CO₃ in refluxing THF takes 30-60 min.

I'd try this option, too.