Re: ORGLIST: methylation of a water-soluble polymer

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From: Manuel Toennis (Manuel.Toennis$##$ch.tum.de)
Date: Wed Sep 22 1999 - 07:20:02 EDT


> To: Multiple recipients of list orglist <orglist$##$dq.fct.unl.pt>
> Reply-to: eugene.leitl$##$lrz.uni-muenchen.de
> From: Eugene Leitl <eugene.leitl$##$lrz.uni-muenchen.de>
> Date: Wed, 22 Sep 1999 00:50:25 -0700 (PDT)
> Subject: Re: ORGLIST: methylation of a water-soluble polymer

> Jacob Zabicky writes:
> >
> > Hello Eugene,
> >
> > An alternative protocol could be that for the preparation of
> > methylcellulose, namely, treating the Na alcoholate of the polymer with
> > CH3Cl.
>
> Hello Jacob,
>
> thank you for your quick response. Unfortunately the polymer (PVA
> copolymer) is virtually unsoluble in THF, ether etc. so I cannot treat
> it with sodium metal. Do you have any suggestions for a good solvent?
>
> TIA,
>
> Eugene

What about DMFor NMP ? You probably cannot use sodium, but LDA or
K-OtBu as base, and methylate with MeJ. If it is only for small
scales, try 'Schwesinger-bases'.
 Alternatively you can try to use diazomethane and a lewis acid,
usually BF3 - but no gurantie (for both casas) for that it will not
also methylate the solvent. You'll have to try.

You cannot use diazomethane in water, beauce diazomethane methylates
the most acidic protons, and this ist the waterproten, compared to
alcohol.


What about treating your polymer with triflic anhydride in THF/Base
and then add Methanol + more Base (eg DIPEA) ?


MT
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