From: Shu-Kun Lin (lin$##$mdpi.org)
Date: Mon Feb 28 2000 - 01:38:17 EST
Dear Dr. Paul Handley:
I would like to invite you to publish this in MolBank section of
MOLECULES as a short note at http://www.mdpi.org/molbank website or
http://www.mdpi.org/mol server.
Even though it is only a slightly improved method there is experimental
procedure useful for other chemists.
Best regards,
Shu-Kun Lin
Managing Editor, Molecules
http://www.mdpi.org/molecules
Paul Handley wrote:
>
> >Dear Friends:
> >I need a simple procedure for the regio-selective allylic oxydationof
> >Limonene (at the acyclic end). I am aware of Crawfords work (JACS, 1972,
> >4298). HOwever, I am always getting about10% impurity, which is difficult
> >to be seperated. I need pure alcohol.
> >Since we cannot purchace n-BuLi used in this procedure, I normally make
> >and titrate it against, a standard (say, diphenyl acetic acid).
> >I would like to know, any other, cleaner and high yielding method for this
> >oxydation.
> >Krish M. Chary
>
> I use this reaction in my own work, and I find it to be very reproducible,
> yield is low, but is as stated by the authors. I always get the 10%
> impurity which the previous authors did not notice in the days before
> capillary gc, but I find it to be easily separated by careful column
> chromatography on silica. Use a rough column first, elute the residual
> limonene with hexane, then do a second column with plenty of silica (at
> least 100:1) and 20% ether/hexane and the 9-hydroxy elutes just before the
> impurity. This gives material pure by gc and nmr.
> There was another way I thought of, ie epoxidise limonene with
> perbenzimidic acid, separate the 8,9-epoxides from the 1,2-epoxides and
> diepoxides by spinning band distillation (yuck) should give you under 50%
> yield (Aust J Chem 1986 39 441), then theres ways to open epoxides to
> allylic alcohols (see Larock, Comprehensive Organic Transformations p116
> for some references) to give the 9-hydroxy, but this way will not be
> simpler or cleaner.
> Unless someone else can come up with a better way, I say stick with
> Crawfords reaction, its not that bad really. I might change my tune if I
> had to make my own BuLi though.
>
> Paul Handley
> Dept. of Chemistry
> University of Queensland
> Brisbane, Australia.
>
> __________________
>
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-- Dr. Shu-Kun Lin Molecular Diversity Preservation International (MDPI) Saengergasse 25, CH-4054 Basel, Switzerland Tel. +41 79 322 3379, Fax +41 61 302 8918 E-mail: lin$##$mdpi.org http://www.mdpi.org/lin/ __________________ORGLIST - Organic Chemistry Mailing List Website and Archive: http://www.orglist.net/ List coordinator: Joao Aires de Sousa (jas$##$mail.fct.unl.pt)
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