Synthesis of CDMT
I have found that 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT) is a useful reagent to assist in the amidation of cinnamic acids. It is easily prepared
from cyanuric chloride.
The procedure given here is basically the one given in "Cyanuric acid derivatives. III Alkoxy-s-triazines" (Dudley, Thurston, Schaefer, Holm-Hansen,
Hull, Adams, July 1951).
Procedure
13.6g cyanuric chloride (73.8mmol) is added to 34g of MeOH, together with 3.8g water (I don't think the exact amounts are terribly important - but
these amounts are scaled from the quantities in the original paper)
Two equivalents of sodium hydrogen carbonate are added, and magnetically stirred at room temperature. The paper says "until most gas evolution has
ceased" but watching the reaction, it isn't very clear when this occurs. Err on the side of too long - too short a time before the next step produces
a low melting point *something* that is definitely not CDMT.
I have stirred for 4 hours with reasonable results.
At the completion of the room temperature stirring, the solution is refluxed for 30 minutes, then allowed to cool to room temperature.
The white crystalline material is filtered and washed well with water, then dried. The paper suggests in a vacuum, but low heat from a hotplate seemed
to work OK.
The raw product is recrystallised from hexane or heptane as white crystals, MP 74 - 75C (lit 74 - 76C). Yield 8.41g @ 175.4 = 48mmol = 65%.
Notes
The cyanuric chloride, if not from a freshly opened container, should be re-crystalised from hexane or heptane.
Cyanuric chloride is very irritating to eyes and nose. Fume hood is required. The resulting CDMT is less irritating, but should still be handled with
care.
During recrystalisation, as the hexane cools, you may notice a dense liquid forming before crystals appear. If you haven't performed the initial
stirring long enough, you will get this. I've found you can pipette out this liquid before the CDMT crystals form and get a reasonable pure product.
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