Sciencemadness Discussion Board

(safer) fluorination of benzaldehyde?

thors.lab - 1-8-2020 at 20:16

Does anybody have any procedures on the fluorination of benzaldehyde that would be suitable for a home-lab setup, not requiring specialized equipment? I am particularly interested in 2-fluorobenzaldehyde, although it would be interesting to investigate other positions as well.

karlos³ - 1-8-2020 at 22:22

You can't directly fluorinate benzaldehyde.
You can oly brominate and then exchange that with fluorine.

2-FA is boring by the way, the 3- position is much more interesting :o

DraconicAcid - 1-8-2020 at 22:44

Diazotization of anthranilic acid, then reaction with fluoboric acid is the only route that comes to mind.

ETA: Oh, wait- you wanted the aldehyde, not the acid. That's not going to work.

[Edited on 2-8-2020 by DraconicAcid]

Sigmatropic - 2-8-2020 at 08:59

Quote: Originally posted by karlos³  

2-FA is boring by the way, the 3- position is much more interesting :o


My guess is that this is going into 2c-x nbf.

DraconicAcid - 2-8-2020 at 09:04

I'm following this thread only in the distant hope that I'll eventually get a benchtop NMR at the college, and would like to show my students coupling to 19F.

clearly_not_atara - 2-8-2020 at 09:17

If diphenylimidazol-2-ylidene carbenes are available, salicylaldehyde can be deoxyfluorinated directly to the target compound:

https://pubs.acs.org/doi/full/10.1021/ja2048072

The fluorination reagent is prepared by the oxidation of an NHC with Cl2 followed by halogen exchange.

symboom - 2-8-2020 at 14:15

Electrochemical fluorination
Where Flourine is made in situ and used up as soon as it's made its a process that os employed to avoid dealing with fluorine gas directly. That's the only kind of fluorination technique I think that may be possible and safest in an amature setting

Syn the Sizer - 2-8-2020 at 18:03

Quote: Originally posted by Sigmatropic  
Quote: Originally posted by karlos³  

2-FA is boring by the way, the 3- position is much more interesting :o


My guess is that this is going into 2c-x nbf.


My guess was 2-FMA. For 2c-x he would want to fluoronate the 4 position, which is easy when the 2 and 5 position are filled with a methoxy group.

[Edited on 3-8-2020 by Syn the Sizer]

draculic acid69 - 2-8-2020 at 18:56

I'd just buy some.

Syn the Sizer - 2-8-2020 at 19:20

Quote: Originally posted by draculic acid69  
I'd just buy some.


You know where to buy 2-FA/2-FMA? Or do mean the 2-fluorobenzaldehyde?

thors.lab - 2-8-2020 at 21:43

Thanks for the help guys. What I'm getting here is that half of you are saying no, there's no simple and cost-effective way to fluorinate benzaldehyde selectively. I figured.

The other half seems to be obsessed with what nearly illegal compound I wanted to make. The answer is that I'm only here to make absolutely, unequivocally legal compounds.

2-FMA

thors.lab - 2-8-2020 at 21:46

Quote: Originally posted by karlos³  
You can't directly fluorinate benzaldehyde.
You can oly brominate and then exchange that with fluorine.

2-FA is boring by the way, the 3- position is much more interesting :o


This makes me wonder if anybody has researched 2-BrMA?

Syn the Sizer - 3-8-2020 at 07:09

I am sure it has all been researched, but maybe not fully documented publically.

The reason we think you are making an illegal compound is, what else are you going to use 2-fluorobenzaldehyde for? Before assuming I googled as I always do, to see what the compound could be used for and 2-FA/2-FMA were the only things I could find aside from sites selling 2-fluorobenzaldehyde.

Do you mind me asking what your legal use is, I am very curious.

deep_dreamer - 3-8-2020 at 08:29

If you pay attention to the steganography in his post, you'd see that he has just that in mind.

I'd doubt that there is a cost-effective route for the synthesis, and all the reagents needed are probably more suspicious/expensive than buying your starting aldehyde in the first place. Unless your goal is actually making 2-fluorobenzaldehyde, and the subsequent reaction steps are just part of a strange side project.

[Edited on 3-8-2020 by deep_dreamer]

Pumukli - 3-8-2020 at 11:56

Symboom, do you know anything particular about the electrochemical route(s) of fluorination?

This is entirely new to me I admit.
Is it really amateur friendly?

I thought that a Balz-Schieman reaction may be the most amateur "friendly" way but if you know a thing or two about an alternative route, please, speak up! :-)

Dr.Bob - 3-8-2020 at 15:45

Quote: Originally posted by symboom  
Electrochemical fluorination - Where Flourine is made in situ and used up as soon as it's made its a process that os employed to avoid dealing with fluorine gas directly. That's the only kind of fluorination technique I think that may be possible and safest in an amature setting


Having worked in a fluorine chemistry company (many years ago, with my friend Ed), as well as trying to make some more recent fluorochemicals, I can safely say that using direct fluoronations, even with electrochemistry, is not well within the scope of most home chemists. Frankly, making almost any flurochemical is really tough, other than maybe the mentioned "Diazotization..., then reaction with fluoboric acid, which does work pretty well.

Just trying to figure out what you have made is tough, even with 19F NMR, which I have had to do before. At least fluorine 19 is abundant, unlike 13C. But 19F NMR is not easy, at least to me.

thors.lab - 4-8-2020 at 00:11

Quote: Originally posted by Syn the Sizer  
I am sure it has all been researched, but maybe not fully documented publically.

The reason we think you are making an illegal compound is, what else are you going to use 2-fluorobenzaldehyde for? Before assuming I googled as I always do, to see what the compound could be used for and 2-FA/2-FMA were the only things I could find aside from sites selling 2-fluorobenzaldehyde.

Do you mind me asking what your legal use is, I am very curious.


1. Synthesis of 2-FMA is not explicitly illegal. It could be argued that it would be illegal but it could also be argued otherwise.

2. I don't have to do anything with the 2-fluorobenzaldehyde, perhaps that's my end product.

3. I could also perhaps be researching derivatives too far removed from amphetamine to constitute as an analog

4. I'm not even planning to do such a synthesis anyway, mostly just curious.

[Edited on 4-8-2020 by thors.lab]

thors.lab - 4-8-2020 at 00:17

Quote: Originally posted by Dr.Bob  
Quote: Originally posted by symboom  
Electrochemical fluorination - Where Flourine is made in situ and used up as soon as it's made its a process that os employed to avoid dealing with fluorine gas directly. That's the only kind of fluorination technique I think that may be possible and safest in an amature setting


Having worked in a fluorine chemistry company (many years ago, with my friend Ed), as well as trying to make some more recent fluorochemicals, I can safely say that using direct fluoronations, even with electrochemistry, is not well within the scope of most home chemists. Frankly, making almost any flurochemical is really tough, other than maybe the mentioned "Diazotization..., then reaction with fluoboric acid, which does work pretty well.

Just trying to figure out what you have made is tough, even with 19F NMR, which I have had to do before. At least fluorine 19 is abundant, unlike 13C. But 19F NMR is not easy, at least to me.


That's a shame! It would be some interesting chemistry to explore.

draculic acid69 - 4-8-2020 at 02:45

Quote: Originally posted by Syn the Sizer  
Quote: Originally posted by draculic acid69  
I'd just buy some.


You know where to buy 2-FA/2-FMA? Or do mean the 2-fluorobenzaldehyde?


I was talking about the aldehyde.i don't really care for the other compounds

Syn the Sizer - 4-8-2020 at 10:00

@draculic acid69 Yes me too, I am interested in the science of it all though.

@thors.lab In some jurisdiction it is illegal as an analogue, in others not at all. Wikipedia lists 3 countries where it is a scheduled substance, Canada, Germany and The UK, obviously in the US under the Federal Analogues Act.

I was genuinely interested in what your plan was. If it is literally just to explore the theoretical reaction awesome, it you are planning to attempt the synthesis even cooler. If you really are exploring a distant cousin I am interested in the outcome of it.

Though you did state it was purely curiosity, that is what fuels science. Don't loose the curiosity.

Tellurium - 4-8-2020 at 12:05

Well I would diazotize 2-Aminobenzyl alcohol with Fluoroboric acid(Just HF + Boric acid). The Diazonium salt can easily be isolated. The dry salt is carefully heated to drive out BF3 and you end up with 2-Fluorobenzyl alcohol. This can then be turned to the aldehyde via the classic methods(Most easy method by far is NaOCl and TEMPO-Catalyst, I also used the more easy produced or cheaper bought 4-Hydroxy-TEMPO).
I guess that is one of the most safe methods of fluorination of aromatics. The BF3 still isn't harmless, but its way better safer than other methods, especially those involving elemental fluorine.

thors.lab - 5-8-2020 at 08:27

Quote: Originally posted by Syn the Sizer  
@draculic acid69 Yes me too, I am interested in the science of it all though.

@thors.lab In some jurisdiction it is illegal as an analogue, in others not at all. Wikipedia lists 3 countries where it is a scheduled substance, Canada, Germany and The UK, obviously in the US under the Federal Analogues Act.

I was genuinely interested in what your plan was. If it is literally just to explore the theoretical reaction awesome, it you are planning to attempt the synthesis even cooler. If you really are exploring a distant cousin I am interested in the outcome of it.

Though you did state it was purely curiosity, that is what fuels science. Don't loose the curiosity.


I am in the US. The federal analogue act "allowed any chemical 'substantially similar' to a controlled substance listed in Schedule I or II to be treated as if it were listed in Schedule I, but only if intended for human consumption." That last clause there is key. It's highly debated, but it is there, and so it could be argued that synthesizing this compound would not be illegal.

Either way, if I just wanted to get high this wouldn't be the way of going about it. "The real deal" is easier to make anyway and substantially cheaper.

But I'm glad you're not against exploring this compound for its chemistry — many would be. I guess we're all mad scientists here!

thors.lab - 5-8-2020 at 08:33

Quote: Originally posted by Tellurium  
Well I would diazotize 2-Aminobenzyl alcohol with Fluoroboric acid(Just HF + Boric acid). The Diazonium salt can easily be isolated. The dry salt is carefully heated to drive out BF3 and you end up with 2-Fluorobenzyl alcohol. This can then be turned to the aldehyde via the classic methods(Most easy method by far is NaOCl and TEMPO-Catalyst, I also used the more easy produced or cheaper bought 4-Hydroxy-TEMPO).
I guess that is one of the most safe methods of fluorination of aromatics. The BF3 still isn't harmless, but its way better safer than other methods, especially those involving elemental fluorine.


This is interesting. Can anybody chip in on whether this could work?

Now the question is synthesizing 2-aminobenzyl alcohol. haha.

Syn the Sizer - 5-8-2020 at 08:48

Quote: Originally posted by thors.lab  
Quote: Originally posted by Syn the Sizer  
@draculic acid69 Yes me too, I am interested in the science of it all though.

@thors.lab In some jurisdiction it is illegal as an analogue, in others not at all. Wikipedia lists 3 countries where it is a scheduled substance, Canada, Germany and The UK, obviously in the US under the Federal Analogues Act.

I was genuinely interested in what your plan was. If it is literally just to explore the theoretical reaction awesome, it you are planning to attempt the synthesis even cooler. If you really are exploring a distant cousin I am interested in the outcome of it.

Though you did state it was purely curiosity, that is what fuels science. Don't loose the curiosity.


I am in the US. The federal analogue act "allowed any chemical 'substantially similar' to a controlled substance listed in Schedule I or II to be treated as if it were listed in Schedule I, but only if intended for human consumption." That last clause there is key. It's highly debated, but it is there, and so it could be argued that synthesizing this compound would not be illegal.

Either way, if I just wanted to get high this wouldn't be the way of going about it. "The real deal" is easier to make anyway and substantially cheaper.

But I'm glad you're not against exploring this compound for its chemistry — many would be. I guess we're all mad scientists here!


For sure, and truth is there is all kinds of crap you can do with an aldehyde and grignard reaction, or many other reactions.

JJay - 6-8-2020 at 18:07

Why not start with toluidines? You could diazotize and react with fluoroboric acid, then add a carbonyl group with chromyl chloride or perhaps by dichlorinating the methyl group under UV light and hydrolyzing it with hydrochoric acid or something.

Fluoroboric acid looks rather nasty and is probably not something I'd want to handle outside of an OSHA-compliant environment except maybe in tiny quantities.

Newton2.0 - 23-3-2021 at 18:53

You've probably figured this out, but depending on your location, there are places that offer 3-F-benzoic acid...

Sjoot me a DM if you are curious about it!

DraconicAcid - 23-3-2021 at 21:25

Alright, I'll bite. What's so special about 3-fluorobenzoic acid?