Ciba-Geigy metolachlor process

Figure 3.36 a The original Josiphos ligand b the Ir-xyliphos complex used in the Ciba-Geigy metolachlor process. 

Until now, only a small number of industrial applications has been reported. The metolachlor process was originally was developed in the Central Research Laboratories of Ciba-Geigy (now Solvias), but is now operated by Syngenta. With a volume of >10 000 ty it is the largest known enantioselective catalytic production process [24—26]. 

Space limitations do not allow every procedure of importance to be mentioned, but one that should be included is the production process for (S)-metolachlor, a herbicide marketed under fhe trade name Dual Magnum by Syngenta (formerly Ciba-Geigy). Volume-wise, this presently constitutes fhe largest production process of any kind applying an asymmetric reaction, with its aimual capacity of more than 10000 tonnes [35]. The efficiency obtained in fhis method based on a planar... 

In comparison to Rh and Ru catalysis, Ir-catalyzed hydrogenation developed much later and still is used much less in industry. The discovery by a Ciba-Geigy team [107] that Ir catalysts are superior to Rh and Ru for the hydrogenation of N-aryl imines, culminating in the development of the (5)-metolachlor process (see below) gave Ir catalysis a strong boost. 

The most important application of Ir catalysis is for the manufacture of (S)-metolachlor. Racemic metolachlor is the active ingredient of Dual , one of the most important grass herbicides for use in maize and a number of other crops. In 1997, after years of intensive research. Dual Magnum with a content of approximately 90% (l S)-diastereomers and with the same biological effect at about 65% of the use rate was introduced by Ciba-Geigy in the USA and is now produced by Syngenta on a scale of >10,000 t/year [109], This chiral switch was made possible by the new technical process that is briefly described below. Key step of this new synthesis is the enantioselective hydrogenation of the isolated MEA imine shown in Scheme 46. 

Scheme 46 Production process for (5)-metolachlor (Ciba-Geigy/Syngenta)...

Metolachlor A process for making the herbicide Dual Magnum. Developed by Ciba-Geigy from 1982. The catalyst is a chiral iridium ferrocenyl compound (the Josephson ligand). In 2008, more than 10,000 tons of metolachlor per year were being made by this process. 

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