February 4, 2013
Here’s a safer, less expensive way to make a key intermediate. Inventors N. Lui, J.-D. Heinrich, and C. Funke disclose processes for making agrochemical intermediates, such as compound 3. The compound exists as keto–enol tautomers 2 and 3. The inventors summarize several processes for preparing the compounds, most of which involve hazardous reagents or are too expensive for industrial production.
The inventors’ process is a one-pot reaction that does not involve hazardous chemicals and is said to be inexpensive. The figure outlines the method used to prepare methyl ester 3 by the reaction of dimethyl malonate (1) with ClCH2COCl in the presence of NaOMe. In the procedure, 1 is treated with base and, after cooling, ClCH2COCl is added. The mixture is then hydrolyzed, and the product is isolated as a crude solid in ≈74% yield. It contains as much as ≈50% NaCl, but no details of the purification, final yield, or purity are given.
When the reaction is carried out using diethyl malonate, the product is a mixture of the methyl and ethyl esters. The process does not use expensive reagents, but the lachrymator ClCH2COCl is not a pleasant chemical to use. The process is likely to have waste-disposal problems. (Bayer Cropscience AG [Monheim, Germany]. US Patent 8,318,955. November 27, 2012; Keith Turner)