From: Marko Hapke (marko.hapke$##$mail.uni-oldenburg.de)
Date: Wed Jan 10 2001 - 02:23:40 EST
Hi Witek,
another way to reconvert the butinol moiety is treatment with KOH at
elevated temperatures (for examples S. H. Havens et al. J. Org. Chem.
1985, 50, 1763-1765 and A. G. Mal'kina, Synthesis 1996, 589-590).
An alternative procedure is the Sonogashira reaction of the aryl bromide
with trimethylsilylacetylene in triethylamine and catalytic amounts of a
palladium complex (for example like Pd(PPh3)2Cl2)) and CuI. The
trimethylsilyl group can easily be removed with an excess of anhydrous
K2CO3 in MeOH/THF (1:1). And if you would like to do it without
protecting groups at the acetylene, you can utilize a Negishi Coupling
reaction with ClZnC#C-H (can be generated from n-Buli, acetylene and
anhydrous ZnCl2) and a palladium complex.
Hope this is useful,
Marko
Witek Mozga schrieb:
> Hi Everybody!
>
> I`m trying to synthesize an acetylene derivative, in which the triple
> bond is connected to the aromatic ring. Using the adduct of
> acetylene and acetone (methylbutinol) in Heck reaction I have
> obtained the product depicted below:
>
> Ar-Br + H-C#C-C(CH3)2-OH -> Ar-C#C-C(CH3)2-OH
>
> # symbolizes triple bond
>
> Could anyone tell me how to reconvert the butinol moiety into
> acetylene again? I mean this:
>
> Ar-C#C-C(CH3)2-OH -> Ar-C#C-H + acetone
>
> I heard that you should add an catalytic amount of NaH and distil out
> acetone from the mixture along with another solvent (toluene).
>
> Does anybody have experience in this method?
> Or maybe you could suggest another way to obtain the acetylene
> derivative from methylbutinol?
>
> With Best Regards,
>
> Witek Mozga
>
> mozgaw$##$rocketmail.com
> mozga$##$trimen.pl
> http://www.trimen.pl
>
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