From: Paul Handley (p.handley$##$chemistry.uq.edu.au)
Date: Wed Mar 01 2000 - 23:13:30 EST
>
> Dear Orglist Folks, I'm having some trouble on the separation of
>the compounds named: 6 - bromine - 1,3,3 - trimethyl - [2.2.2] oxabicycle
>octane and 2 - bromine - 2,6,6 - trimethyl - [3.2.1] oxabicycle octane
>(known by literature), a pair of isomers generated in the reaction of alfa
>- terpyneol and NBS in dichlromethane. I've already made plenty of
>unsuccessful attempts of separating these compounds by radial and column
>cromatography on SiO2, while literature describes attempting on liquid
>cromatography, which was unsuccessful too. I shall need one of these pure
>to determine structure by spectroscopic methods. I'll summarize answers to
>the list. Thank you in advance,
> Victor Rodrigues (Graduation - IQ - UFRJ)
Yes you will have a lot of trouble with that, the two compounds
interconvert, you will get about 70% of the cineole and 25% of the pinol
after 3 days at room temp, regardless of starting composition. Theres a
lovely neighboring group effect where the ether oxygen helps kick out the
bromine; 6-alpha-bromocineole hydrolyses in water with a halflife of about
10 minutes.
Why do you want these compounds? they are all described in the literature
Carman and Fletcher Aust. J. Chem. 1986 39 1723-38.
Separating them is not worth your time, if you have to react them further
then do it and separate those products instead.
Paul Handley
Dept. of Chemistry
University of Queensland
Brisbane, Australia
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