poix (Newbee)
05-27-02 14:54
No 314745
      reductive methylation of 1,4 naphtoquinone  Bookmark   

From pihkal, 2C-G-N entry:

SYNTHESIS: A solution of 17.5 g 1,4-naphthaquinone in 200 mL MeOH was heated to the boiling point, and treated with 28.5 g stannous chloride at a rate that maintained a continuous rolling boil. At the completion of the addition, the reaction mixture was saturated with anhydrous hydrogen chloride, and held at reflux on the steam bath for 2 h. The reaction mixture was poured into 700 mL H2O and treated with aqueous NaOH. During the addition there was transient development of a curdy white solid which redissolved when the system became strongly basic. This was extracted with 3x200 mL CH2Cl2 and the pooled extracts were washed first with H2O, then with dilute HCl, and finally again with H2O. Removal of the solvent under vacuum yielded 15.75 g of a low melting black flaky crystalline material which was distilled at 160-180 C at 0.05 mm/Hg to give 14.5 g of an amber, solid mass with a mp of 78-86 C. Recrystallization from 75 mL boiling MeOH provided 1,4-dimethoxynaphthalene as white crystals melting at 87-88 C.

This look like a reductive methylation of quinone without methylating agent (DMS,CH3I...) like what Antoncho searched months ago. Do some bee know this reaction? Could it bee aplied with an amine in solution or will reductive amination occur?I guess it form the diacetal of the quinone which is reducted by Sn after it's formation but really i dont know
 
 
 
 
    Rhodium
(Chief Bee)
05-27-02 22:14
No 314881
      amine, quinone and Me2SO4  Bookmark   

Reacting a quinone with dimethylsulfate forms the "di-hemiacetal". To answer your question you need to give us more information. What amine is it, and what is it doing in the reaction mixture?

What is certain is that dimethyl sulfate reacts with amines to give the mono-, di-, tri- and tetraalkylated amine.
 
 
 
 
    poix
(Newbee)
05-28-02 00:36
No 314932
      2-ethylamino quinone  Bookmark   


post No 264123 antoncho say that  reducing quinones in MeOH leads to dimethoxybenzenes. After some research in the quinone thread we found out that we can reduce quinone in MeOH only to produce p-methoxy phenol and antoncho made a thread on it. Today I was reading pihkal and saw that reaction and there isn't any alkylating agent in it afaik. Shulgin do no use DMS nor CH3I here, he only reduce with Sn and he form the dimethoxy compound and not the mono methoxy.

I have interest in this reaction for not having to protect the amine in 2-ethylamino quinone to transfomr it in 2CH. With CH3I or DMS the amine will bee methylated and we don't which it. I wonder if this reaction can do that without forming nasty byproduct like the polymer of 2-ethylamino quinone with the amine of one molecule attached to the quinone of the other by a reductive amination step taking place with Sn. If Shulgin form the biacetal of the quinone (1,1,4,4 tetramethoxy quinone) before reduct it to 1,4 dimethoxy the carbonyl are acetylated and can't react with the amine and all is cool then. If the mecanism don't begin with the acetalisation of the quinone it will surely not work. Can anyone explain me how this mecnism is going an if polymerisation will occur with 2-ethylamino quinone ?
 
 
 
 
    Rhodium
(Chief Bee)
05-28-02 00:49
No 314937
      I very strongly believe you would have to protect ...  Bookmark   

I very strongly believe you would have to protect the amine for this to work.
 
 
 
 
    Antoncho
(Official Hive Translator)
05-28-02 03:31
No 315003
      !!!  Bookmark   

Wow, Poix! Way cool!

Just to think of it - all this time this proc. was sitting in PiHKAL and i didn't notice it!blush

Unfortunately, can suggest nothing about the possible red. amination - do quinones beehave like ordinary ketones at all (i.e., easily form imines)? If they do, i'd expect that side-reaction to beecome a serious issuefrown

In any case, i'm really glad that procedure was foundwink Should have a very wide range of practical applicationssmile


Antoncho
 
 
 
 
    Rhodium
(Chief Bee)
05-28-02 04:30
No 315021
      Yes, quinones readily form oximes for example - ...  Bookmark   

Yes, quinones readily form oximes for example - they behave like a special case of alpha,beta-unsaturated ketones.