From: alihoyer$##$post.uni2.dk
Date: Thu Jun 10 1999 - 16:43:12 EDT
> You can generate the carbene without a catalyst, so you might not need R=
h
> at all,
This sounds interesting. Generating the carbenoids without rhodium.
Have you got a particulkar reaction in mind?
> and then, a double bond
> is more reactive then a triple bond - at
> least for some reactions - so why not try it just with the enyne
When I try subjecting the enyne to rhodium acetate/diazoacetate, I
get a lot of different products, and the cyclopropene-derived ones
account for a lot of the mass balance. The desired
alkyne-cyclopropane is also among the products, but yields are low
and purity is awful.
> Cobalt - carbonyl - comlexes are used to activate a triple bond - could
> it be the pawson khand reaction ? - and as a carbene is also a good
> ligand, you might get something very messy.
In fact, I do; but mostly I get unreacted cobalt carbonyl alkyne
complex back, under conditions where rhodium acetate/diazoacetate has
never failed to cyclopropanate double bonds.
I haven't seen any signs yet that Pauson Khand type products
(cycloenones) are among the products, by the way.
> (especially as the pk-reaction - if the name is correct - cyclisates a
> double bond, a triple bond and a carbon monoxide to a five membered ring=
> en-ketone.)
>
> I would just put your educts together in an inert solvent and heat them
> till N2 forms (say 50 - 70 °C) and look at the result.
>
> Manuel Toennis
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