From: Plamen Angelov (angelov$##$argon.acad.bg)
Date: Wed Feb 19 2003 - 13:43:03 EST
Have you tried a large excess of the amine? i.e. to dissolve the ester
into excess methyl amine?
According to my observations this approach works fine for ethyl esters of
some tetrahydroisoquinolin-1-yl acetic acids. The corresponding amides are
obtained in good yields after 1-2 days stirring at r.t. Maybe the same
conditions will work in your case.
Best regards.
--- samarium Steiner <neptunium$##$gmx.net> wrote:
> Hello everybody
>
> I'm looking for a method to form an amide directly from an ester and a
> primary amine. Small esters such as methyl- and ethyl formate and
> methyl- and ethylacetate can be heated with the amine affording the
> corresponding formamides or acetamides in good yields. But if the ester
> (the part of the acid) is large, e.g. a cyclohexane carboxylic acid
> ethylester, the yields are bad. One could first hydrolyze the ester and
> then do the coupling (e.g. with BoP, PyBoP or TBTU). But if the ester
> used herein is hydrolyzed, the formed acid is too soluble for its
> isolation of an aquous layer (an tert. amine function is also present ->
> IEP aso).
> Is there any method for its direct transformation?
> (There is a direct method with 2,2,2-trihaloethyl esters using
> phosphorous(III) reagents, but I have to avoid the formation of this
> ester.)
>
> Thank you very much,
>
> samarium
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