From: Manuel Toennis (Manuel.Toennis$##$ch.tum.de)
Date: Thu Jun 10 1999 - 03:28:50 EDT
alihoyer$##$post.uni2.dk wrote:
>
> I consider subjecting an (unconjugated) enyne to Rhodium catalyzed
> cyclopropanation with ethyl diazoacetate. As the triple bond of the
> enyne suffers attack by the carbenoid thus generated (generating
> cyclopropenes in reasonable yields), I have considered protecting the
> triple bond as its dicobalt hexacarbonyl complex.
> Would anybode expect this to work - or not?
> Is Rhodium Acetate compatible with cobalt carbonyls?
> Are there any other ways to protect the triple bond of an enyne from
> cyclopropanation?
Only some 'maybe's':
You can generate the carbene without a catalyst, so you might not need Rh
at all, 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
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.
(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
__________________
ORGLIST - Organic Chemistry Mailing List
Website and Archive: http://www.orglist.net/
List coordinator: Joao Aires de Sousa (jas$##$mail.fct.unl.pt)
This archive was generated by hypermail 2.1.4 : Fri Sep 19 2003 - 12:15:04 EDT