Rhodium (Chief Bee)
11-17-02 18:52
No 380506
      Sonogashira coupling to give phenethylamines  Bookmark   

How can we use this synthesis for our purposes? To make a standard phenethylamine, we'd need to engage acetylene in the Sonogashira coupling (and propyne for amphetamines). Can that be done, or can we use a liquid derivative, like (CH3)3Si-CC-H (or (CH3)3Si-CH2-CC-H for amphetamines) and after the coupling toss the silyl?

Or should we simply abandon Mr. Sonogashira and look for another method of synthesizing arylpropynes? Any suggestions? Preferably we should use an aryl bromide as starting material.

Eur. J. Org. Chem. Vol. 7 Pages: 1213-1220 (2002)

(Hive Bee)
11-17-02 19:32
No 380524
      propiophenone & P2P  Bookmark   

When you do the reaction with propyne, the compound can be a precursor to obtain propiophenone and P2P.

The addition of a molecule of water across the triple bond  (H20, H2SO4 / HgSO4) gives an enol, which rearranges to the ketone  (tautomeric equilibrium).  This gives propiophenone.

A more interesting alternative for the use phenyl-1-propyne would be an addition of borane (B2H6).  This gives the alkene with a BH2 in the 2 position.  Oxidation (H2O2 / OH-) gives a more interesting enol (with the hydroxyl in the 2 position).  This rearranges to P2P.

This is mabey a better alternative, because the Tebbe reagent (Cp2TiMe2) is somewhat exotic ...
I thought in a previous post about the use of the Tebbe reagent in the P2P synthesis (see thread Post 363414 (Cyrax: "alpha-ethylstyrene synthesis (organometalic chem.)", Chemistry Discourse)), but upon further reflection, I thought about it as being a bad idea (at least for large scale synthesis).  Tebbe 's reagent isn't exactly easy to prepare, and I think it woubd be rather expensive (what is the price exactly?).  In the thread, one can find refs. for it's preparation.
(Master Searcher)
11-18-02 02:57
No 380581
      MAPP gas  Bookmark   

MAPP gas has methylacetylene and propadiene in it.  How can you separate out the methylacetylene?

Some metal acetylides are explosive when dry, but I think they're stable when wet from what I remember.  Maybe the methylacetylene can be purified via the copper methylacetylide. 

The hardest thing to explain is the obvious
(Stoni's sexual toy)
11-18-02 09:52
No 380602
      You would have to handle huge amounts of a very ...  Bookmark   

You would have to handle huge amounts of a very dangerous primary explosive!
Maybe you could leave the diene in it since it wouldn't react?
or maybe the sodium acetylide can be prepared, either with NaOH (doubtful) or stronger bases like NaH, NaNH2, KOtBu etc?

I'm not fat just horizontally disproportionate.