Syngenta Crop Protection, Inc.

Bernhard Urwyler

Thomas Rapold

Marco Passafaro

Process for preparing 4,6-dimethoxy-2-(methylsulfonyl)-1,3-pyrimidine by reacting 4,6dichloro-2-(methyltio)-1,3-pyrimidine in an inert organic solvent with an alkali metal methoxide, transfer of the resulting 4,6-dimethoxy-2-(methylthio)-1,3-pyrimidine into an aqueous-acidic medium and subsequent oxidation of this compound, of appropriate in the presence of a catalyst, wherein the oxidation is followed by a purification step in which the aqueous-acidic reaction mixture is adjusted with aqueous base to a pH in the range of 5-8 and stirred either in the presence or in the absence of an organic solvent, and the use of this compound for preparing herbicides, for example 7-&lsqb;(4,6-dimethoxy-pyrimidin-2-yl)thio&rsqb;-3-methylphthalide.

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Schweizerhalle, Switzerland

Bernhard Urwyler