cilliersb (Hive Bee)
02-13-02 04:37
No 269062
      possible easy DOB  Bookmark   

OK Beez, Here goes.

H2SO4 and MeOH to form Sodium Methyl Sulphate. Use this to dimethylate Hydroquinone to give 1,4-DimethoxyBenzene. Brominate this in GAA with (NaBr H2SO4 H2O2) to give 1,4-DimethoxyBromoBenzene. Now condense this with Acetone enolate to 2,5-Dimethoxy-P2P. Now just an Al/Hg with Nitromethane to 2,5-DMA and Brominate the product.

DOB Violla

Any ideas if this could work?
(Hive Prodigy)
02-13-02 04:53
No 269069
      Re: possible easy DOB  Bookmark   

Al/Hg with hydroxylamine you mean. Nitromethane would give the N-methyl analog, which is undesireable. Yes, it will work, and has been thought of before. smile

I have often wondered if the extreme bases such as alkoxides, may rip up your methyl ethers.

And I wouldn't call it easy. Definitely possible, but not easy.

There are some harder ways, but there are definitely some easier ways, too. wink


The Water Will Be Your Only Mirror
(Chief Bee)
02-13-02 06:24
No 269095
      Re: possible easy DOB  Bookmark   

You better use 1,4-dimethoxybenzene and acetone/Mn(III)acetate instead of what you propose to make 1,4-dimethoxy-P2P. I have a feeling the electron-donating methoxy groups would hinder the reaction. If you want to try it out, then try it with plain benzene and acetone enolate first.
(Hive Bee)
02-13-02 06:36
No 269100
      Re: possible easy DOB  Bookmark   

Sorry about the mistake with Nitrometh, of course it's Hydroxylamine....... I'm getting ahead of myself again.

Well, this seems the best way for me to get there. The only procedure here that I'm not sure about is the bromination of 1,4 DiMeOBenzene to 2,5 DiMeOBromoBenzene, I think it may Brominate multiple positions. Is there any way to know for sure that no diBromo or even tetra or Hexa bromo will form.

Yes, I know that no sunlight and low temp will help for this step.

You mentioned easier methods, wanna PM me?

Oops, seems Rhod and I were posting at the same time. This just confirms my fears. That Mn(III) synth makes me down right sad, the yeild makes it almost unworkable. I'm not going to use 500g of HQ to produce only 20g of precursor.

Anyone got any other (BETTER) ideas.

Thanks for the feedback Rhodium!!smile  I don't know how you do it, but you're everywhere.
(Chief Bee)
02-13-02 07:26
No 269115
      Re: possible easy DOB  Bookmark   

Of course you recycle unreacted dimethoxybenzene in the Mn(III) reaction. Either the product P2P is formed, or the molecules are left untouched.

It is easy to brominate dimethoxybenzene in one single position, use 1 eqv of bromine and glacial acetic acid as solvent.
(Hive Bee)
02-13-02 08:08
No 269131
      Re: possible easy DOB  Bookmark   

Thanks again Rhod

This really cleared things up quite a bit. Just involves a lot of synthing getting to my xxP2P that way.

If this works the hive can expect a full writeup from HQ to DOB with pictures and yeilds for every step.

I'm sure everyone here understands that it may take a substantial amount of time to complete such a project, so be patient for feedback.

I see now that the problem is with the enolate reaction to form xxP2P and not with the bromination. Mn(III) it is then.

DOB smiles for everyonelaughlaugh
(Hive Addict)
02-13-02 11:56
No 269239
      Re: possible easy DOB  Bookmark   

>It is easy to brominate dimethoxybenzene in one single
>position, use 1 eqv of bromine and glacial acetic acid as solvent.

However, do remember that you'll always have some unreacted dimethoxybenzene left. Not that is matters much; 2-bromo-1,4-dimethoxybenzene is a liquid, and dimethoxybenzene and the dibromo compound are both solids at RT, so apart from the small amounts of the latter two that dissolve in the monobrominated stuff, they are easy to separate.
(Chief Bee)
02-13-02 12:42
No 269255
      1,4-MeO-Ph --AcOH/Br2--> 2,5-MeO-PhBr (90%)
(Rated as: good read)

1,4-Dimethoxybenzene (10g, 72.4 mmol) was dissolved in 100ml HOAc. 4.0ml elemental bromine in 50ml HOAc was added dropwise during 1h. The stirring was continued for a further hour, the solution diluted with 200ml water, extracted with 2x50ml diethyl ether, the pooled etheral extracts was washed with 2x25ml water, 25ml 5% NaOH, dried over MgSO4 and the solvent evaporated. Yield 14.15g (65.21 mmol, 90%) of 2,5-dimethoxybromobenzene as a colorless oil.

Acta Chem Scand 53(9), 714 (1999)