From: Jacob Zabicky (Jacob.Zabicky$##$uab.es)
Date: Mon Apr 03 2000 - 04:55:37 EDT
Hello Glen,
Just a couple of hints. The first reactions of olefins children learn about
is halogen, and in particular bromine, addition. This sounds decievingly
simple. The best is to heed the advise in Organic Synthesis aut the
preparation of 1,2-dibromocyclohexane from,cyclohexane, namely, freshly
distilled olefin, cooling, and careful addition of the bromine. If you use
your olefin from the bottle, it may contain peroxides and your product ends
up as a fuming mess. PROTECTION FROM LIGHT, wrapping your reacting vessel
with Al foil, may also contribute to a purer product.
Jacob
>Hello, all. I am trying to synthesize compounds with the following
>molecular structure: RBrC(double bond)CBrR, where the halogens are
>preferably trans to each other. An example would be
>trans-2,3-dibromo-2-butene, which would have pendant methyl groups.
>Ideally I'd like to have control over the identity of the alkyl groups,
>which would hopefully come from commercially available precursors (alkyl
>bromides, alcohols, aldehydes, etc).
>
>So far I've tried transforming trans-2,3-dibromo-1,4-dihydroxy-2-butene
>into the 1,2,3,4-tetrabromo-2-butene with PBr3, followed by reaction
>with alkyl Grignard reagents. However, this gives me a complex mixture
>of (allylic rearranged) products. While I can make the dialkoxy
>versions easily, they are not any good for my particular reaction, they
>have to be alkyl.
>
>Does anyone have any experience in this type of synthesis that would
>like to share? All opinions gratefully :) accepted via email. Thanks
>in advance!
>
>Glen Brizius
*********************************************************************
Prof. Jacob Zabicky Tel.: +94 93 581 1401
Group de Física dels Materials II Fax.: +94 93 581 2155
Universitat Autònoma de Barcelona Private:
08193 Bellaterra (Barcelona) Tel.: +94 93 581 7485
Spain
*********************************************************************
*********************************************************************
Temporary address:
Prof. Jacob Zabicky Tel.: +34 93 581 1401
Group de Fisica dels Materials II Fax.: +34 93 581 2155
Universitat Autonoma de Barcelona Private:
08193 Bellaterra (Barcelona) Tel.: +34 93 581 7485
Spain
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