vendredi 18 mai 2007


I would like to present you today a reaction I have performed a long time ago (in a galaxy far, far away....), and which can be very useful for different purposes.

As you probably know or should know , the regioselective chlorination of pyridine or quinoline N-oxide in the position 2 can be achieved by treatment with phopshorous oxychloride as chlorinating agent.

But, I have realized this reaction on the pyrazine-1,4-dioxide, if you apply the "classic" mechanism on this structure, you should have either the 2,5-dichloro or 2,3-dichloropyrazine, but of course it is not the case and the only compound isolated is the 2,6-dichloropyrazine.

Unfortunately, I have no explanation for this I only know that when the position 6 is blocked then the chlorination occurs in 5 and when position 6 and 5 are blocked the chlorination is in 3.
A don't have the exact references but they were J Het Chem in the mid 80's from a Yamamoto.

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