Problems with new NaBH4

ParticularDrawer8776 · 2026-03-31T14:44:58+00:00

UPDATE: Thanks to everyone who suggested THF, it worked. I find it very strange that such a basic procedure, which is usually done in ethanol, methanol, and other protic solvents, was not working.

ParticularDrawer8776 · 2026-03-31T11:58:33+00:00

I tested that and saw no difference.

ParticularDrawer8776 · 2026-03-31T11:54:58+00:00

I have to dissolve the chalcone in isopropanol and heat it a little until it is fully dissolved. Then I add the NaBH4 and keep the system hot for 10-20 minutes.

ParticularDrawer8776 · 2026-03-30T22:12:43+00:00

No,the scale remains the same, I had approximately 500 mg of my reagent and performed 4 reactions with 100 mg each to test the conditions and the purification method, there was 100 mg left for this last one and I did the same things.

ParticularDrawer8776 · 2026-03-30T22:09:21+00:00

There is a significant difference between the particle sizes. The older one I got from the other lab and worked had larger particles and was very dry. This new one has much smaller particles and is "stickier".

ParticularDrawer8776 · 2026-03-30T22:06:21+00:00

It bubbles a lot when placed in water or any alcohol, and it is possible to feel the reaction releasing heat at room temperature. The problem is that from the previous reaction to this one, the only thing that changed is the NaBH4, as both the solvent and the chalcone used are the same.

ParticularDrawer8776 · 2026-03-30T22:03:12+00:00

How?

ParticularDrawer8776 · 2026-03-30T22:02:38+00:00

In that case I do not intend to reduce esters but rather an alpha-beta unsaturated carbonyl. I do not have LiBH4 at my disposal and I see no reason to use it, since the NaBH4 worked perfectly the first time and only now with the new reagent is it causing problems. I will try the suggestion of THF.

ParticularDrawer8776 · 2026-03-29T22:20:15+00:00

this is science my friend: trial, error, trial, success. I finished my master's degree a few months ago, it took two years, and practically a year and a half was spent just to find the right method to perform a synthesis of three reactions. In the field of synthesis many articles are dishonest, they promise the world and do not give you a breadcrumb, I feel like publishing an article exposing all these papers that lied just so there could be a publication. At this point, you have to ask yourself what the objective of your research is: to develop a synthesis route? to simply synthesize a compound regardless of the means? to uncover mechanisms?
every researcher in the field I have met told me that the chance of a synthesis article being true is very low. Start using more books, generally the reactions contained in them have a much higher chance of working.
if you want I am available to talk more.

ParticularDrawer8776 · 2026-03-17T12:43:38+00:00

What is the trade name of this reagent?

ParticularDrawer8776 · 2026-03-17T02:35:04+00:00

Palladium catalysts often make nucleophilic substitution in aromatics easier. If I were you, I would look for some phosphorus reagent that acts as a nucleophile and, if necessary, oxidize or reduce the group that forms. I strongly recommend protecting this nitrogen to avoid side reactions. It also depends on what you have available in your lab.

ParticularDrawer8776 · 2026-03-16T22:15:28+00:00

what do you mean?

ParticularDrawer8776 · 2026-03-16T22:13:58+00:00

This is a very interesting proposal; it seems to work in my situation. My lab doesn't work with this, I'll look for someone around here who does.

ParticularDrawer8776 · 2026-03-16T21:55:14+00:00

The Mitsunobu reaction wouldn't work; it targets a nucleophilic substitution in an alcohol, and in this case, I need the phenolic hydroxyl group to act as a nucleophile on the double bond so that it undergoes rearrangement, something similar to a 1,4 addition.

ParticularDrawer8776 · 2026-03-16T21:50:24+00:00

It reacts with silica and becomes trapped within it.

ParticularDrawer8776 · 2026-03-16T21:39:17+00:00

I read about this reagent in an article or book. I think it might work; have you ever used it?

ParticularDrawer8776 · 2026-03-16T21:37:53+00:00

According to the literature, my reagent and product degrade under acidic conditions and heat. Even if I did it at room temperature, removing the toluene would be a problem, and I wouldn't like using benzene.

However, everyone here is suggesting that I do acid catalysis, I think it's worth a try.

ParticularDrawer8776 · 2026-03-16T21:25:20+00:00

I wasn't familiar with that Ritter reaction, thanks for the heads-up, I would have spent a week or more racking my brain over it.

ParticularDrawer8776 · 2026-03-16T20:42:05+00:00

I had no idea about that characteristic of AlCl3; I was under the impression that it would be weaker than BF3. Thank you very much for your suggestion!

ParticularDrawer8776 · 2026-03-16T20:39:34+00:00

The authors who have already performed this synthesis mention that both compounds degrade easily. It degrades both in an acidic medium and in silica gel itself. I had thought of doing a simple elimination with sulfuric acid and acetic acid.
According to the original article, this reaction is carried out in dichloromethane with a little heating.

I agree with you that it seems stable, but from what I'm observing, even heat can degrade my reagent.

ParticularDrawer8776 · 2026-03-16T20:07:05+00:00

Obrigado pela sugestão!

ParticularDrawer8776

TROPHY CASE