From: Jack Kellum (jkellum$##$ucsd.edu)
Date: Tue Oct 26 1999 - 12:41:43 EDT
Jonathon,
Check out the following reference: Armstrong, A.; Brackenridge, I.;
Jackson, R. F. W.; Kirk, J. M. Tetrahedron Letters 1988, 29, 2483-2486. It
describes the use of t-butyl-trichloroacetimidate to form t-butyl esters and
ethers in good yield. The reagent is now commercially available from
Aldrich and I've obtained quite good yields (>85%) when esterifying amino
acids. The conditions are quite gentle (room temperature in DCM with a cat.
amount of boron trifluoride etherate). The acetimide byproduct can be
removed by crystallization and filtration.
Also check out Widmer, U. Synthesis 1983, 135-136 which uses
N,N-DMF-di-t-butyl acetal, also available from Aldrich. This is also quite
effective but requires reflux in toluene.
Good luck,
Jack Kellum
----- Original Message -----
From: celtichem ltd <celtichem$##$hotmail.com>
To: Multiple recipients of list orglist <orglist$##$dq.fct.unl.pt>
Sent: Tuesday, October 26, 1999 9:31 AM
Subject: ORGLIST:
> Hi,
>
> starting from malonic acid labelled in the 2 position, what would be the
> best way to prepare the di-t-butyl esters, wiythout causing
decarboxylation.
> I am considering either of the following:
>
> DCC + tBuOH
>
> or SOCl2 followed by t BuOH.
>
> Any comments? or other suggestions?
>
>
> best wishes,
>
>
>
> Jonathan A Adams.
>
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