Sciencemadness Discussion Board

Bromination of 1,3 benzodioxole to 5-Bromo-1,3-benzodioxole?

Chemist1357 - 27-11-2022 at 06:10

Any way to do this without NBS that is more available to the amateur?

Could it be done with Using Ammonium Bromide and H2O2 in Acetic Acid?
Ammonium bromide is easily prepared using HBr and ammonia.

(Taken from Erowid) https://erowid.org/archive/rhodium/chemistry/aromatic.bromin...

Experimental
General Procedure for the Bromination of Anilines and Anisoles

A 25 mL two-necked round bottomed flask was charged with the substrate (2 mmol) and ammonium bromide (2.2 mmol) in acetic acid (4 mL). A 30% H2O2 (2.2 mmol) was added dropwise to the reaction mixture and the contents allowed to stir at room temperature. The reaction was monitored by thin layer chromatography (TLC). After the completion of the reaction, the reaction mixture was treated with saturated sodium bicarbonate solution and extracted with dichloromethane. The organic extract was dried over anhydrous sodium sulfate and solvent evaporated under reduced pressure.

This could be done to 1,3 benzodioxole correct? Or will you end up with something else...

[Edited on 27-11-2022 by Chemist1357]

clearly_not_atara - 27-11-2022 at 21:01

Table 2, entry 8.

Pumukli - 28-11-2022 at 09:07

_not_Atara, clearly you have a wicked sense of humor. :)

But you were 100% honest, I checked.

Table 2, entry 8 tells everything.

Unfortunately it is not the wanted isomer, but that's life and organic chemistry in action.

Chemist1357 - 29-11-2022 at 03:26

Quote: Originally posted by Pumukli  
_not_Atara, clearly you have a wicked sense of humor. :)

But you were 100% honest, I checked.

Table 2, entry 8 tells everything.

Unfortunately it is not the wanted isomer, but that's life and organic chemistry in action.


How is it not the wanted isomer? What is the obtained product then?

Pumukli - 29-11-2022 at 03:48

You put a question mark to the end of your opening sentence, hence I assumed you were looking for a route to 5-bromo-isomer. (ie: your wanted isomer was the 5-bromo-compound.)

Table 2, entry 8 says the product is exclusively the 3-bromo-isomer.

If you were after the 3-bromo, that's fine, you can get it in good yield from the reaction. If you wanted to produce the 5-bromo then the described route is obviously not the proper one.

Btw. I think the 5-bromo-numbering is not good, not IUPAC compatible at least. 3-bromo: the bromine goes to the first carbons that are the immediate neighbours of those that have the O attached. 4-bromo: the bromine goes to the second carbon from the O-bearing one. 5-bromo: I can't understand this, due to the symmetry of the molecule.

clearly_not_atara - 29-11-2022 at 05:21

Pumukli: There is a footnote signifier by the entry, but the footnote is obviously wrong, because it says something about a naphthalene (impossible). Should download the actual paper to check.

Pumukli - 29-11-2022 at 06:00

Atara, (or not), thanks for the reminder!

Here we go:


Attachment: krishnamohan2004.pdf (152kB)
This file has been downloaded 140 times


It seems, that this table is a bit different than on the rhodium site. :) And the mystery of "naphthalene" also got solved. :)

[Edited on 29-11-2022 by Pumukli]

[Edited on 29-11-2022 by Pumukli]

Boffis - 29-11-2022 at 06:30

Hi Pumikli, I think the difference in the numbering is due to the fact it is regarded as a benzo-heterocyclic rather than a benzene derivative so the numbering goes like this:

Benzodioxole.gif - 3kB

Like you say there seems to be a fairly fundamental difference between the Rhodium table and the original paper. I presume that, as you say, the "p" isomer is the 5 isomer and the "o" isomer is position 4

Pumukli - 29-11-2022 at 06:32

Yeah, you are right, Boffis, my fault! :)

Anyway, the "real deal" table shows a very different picture!

Mateo_swe - 29-11-2022 at 06:35

Couldnt just liquid bromine be used, or would that put the bromine in wrong position?

Pumukli - 29-11-2022 at 07:01

Maybe the orientation would be different.
Maybe the availability is different (for an amateur).

Chemist1357 - 29-11-2022 at 07:14

Quote: Originally posted by Mateo_swe  
Couldnt just liquid bromine be used, or would that put the bromine in wrong position?

In acetic acid yes yields are around 70% and you get the dibromide as well.
Also screw working with Br2 when you could use a much nicer bromide salt such as ammonium bromide (i'm hoping)

[Edited on 29-11-2022 by Chemist1357]

Mateo_swe - 29-11-2022 at 12:36

Now i remember, what i was refering to.
It was a bromination of protocatehuic aldehyde (3,4-Dihydroxybenzaldehyde).
That aldehyde can be brominated with bromine in chloroform resulting in 2,5-dibromo-3,4-dihydroxybenzaldehyde.
Not the same as 1,3-Benzodioxole obviously, i was just remembering wrong and got them mixed up.
Sorry about that.

[Edited on 2022-11-29 by Mateo_swe]

I got what you need son....

Johnny Windchimes - 20-12-2022 at 04:42

Truly the best way IMO.

If you cant find HBr, make it from NaBr.

If you cant find 30% H2O2, make it by slowly and carefully boiling down regular 3% H2O2 until it's to your desired concentration.

BE WARNED: YOU MUST vacuum distill the final product; it'll scorch and turn to tar otherwise.


It's worth it, even if you have to make the hydrobromic acid, it's easy if not tedious. I'll never use elemental bromine or NBS or anything like that again!


Good luck~!






Attachment: Dat 5-Bromo Narc Paper - Copy.pdf (1.8MB)
This file has been downloaded 118 times 5-Bromo - Copy.jpg - 141kB

P.S. Not dead, just been busy.... for over a year....

[Edited on 20-12-2022 by Johnny Windchimes]