thegameguy5 - 6-9-2005 at 14:53
Hi Guys
I am trying an intramolecular radical cyclization reaction using AIBN/TBTH in Tol or PhH for a while but in vain.
Does anyone have any correct procedure or hand on experience to share with me?
Thanks
Sandmeyer - 7-9-2005 at 12:31
There is an enormous amount of publications on the topic - I have various references as well, but you'll have to be more specific, what exactly
are you trying to do?
thegameguy5 - 7-9-2005 at 22:51
I am making an exo-methylene cyclohexane derivative.
It's sugar chemistry. I have a xanthate and I want to generate a radical at C-5 (of tetrabenzyl protected glycose deriative) which will undergo a
radical deoxygenation cyclization reaction on an acetylene moiety. I have tried AIBN, Et3B / TBTH in PhH or Tol but so far I have not been successful.
I have degassed my solvent with N2 without any improvement so now I am going to degass it with Ar.
Have you had any trouble working with radicals?
Thanks
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Sandmeyer - 8-9-2005 at 01:25
Here is a paper where functional groups of your interest react to give the alkene. They do the cyclization in toluene at 85C with HBu3Sn/AIBN, after
12 h there is 76 % yield.
http://rapidshare.de/files/4853622/radical.pdf.html
Stereodivergent synthesis of 5a-carba-hexopyranoses from carbohydrates via 6-exo-dig radical cyclization: preparation of 5a-carba-@b-d-manno-,
@a-d-allo-, @b-l-talo- and @a-l-gulopyranose pentaacetates from d-mannose
Gomez, Ana M.; Moreno, Eduardo; Danelon, Gerardo O.; Valverde, Serafin; Lopez, J. Cristobal; Tetrahedron: Asymmetry; 14; 19; 2003; 2961 - 2974.
Abstract: Four carbasugars, 5a-carba-@b-d-manno-, @a-d-allo-, @b-l-talo- and @a-l-gulopyranose pentaacetates, have been prepared in a
stereodivergent manner from d-mannose. Alkynyl derivatives of 2,3:4,6-di-O-isopropylidene-d-mannopyranose, which are prepared by homologation at C-1,
by reaction with phenyl acetylide, undergo a 6-exo-dig radical cyclization, from a radical located at C-5, to yield a mixture of highly functionalized
cyclohexanes. Some of these compounds, after transformation of their exocyclic double bond in a hydroxy function, were correlated with
polyhydroxylated cyclohexanes, which were then selectively deoxygenated either at position C-4 or C-5a (carbohydrate numbering) to afford carbasugars
of the d- or l- series.
And references in there...