DUAL MAGNUM®, metolachlor

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 1996, after years of intensive research, Dual Magnum with a content of approximately 90% (S)-diaste-... 

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% (I S)-diastereomers and with the same biological effect at about 65% of the use rate, was introduced into the market. This chiral switch was made possible by the new technical process that is briefly described below. The key step of this new synthesis is the enantioselective hydrogenation of the isolated MEA imine, as depicted in Figure 1.3. 

The reduction of metolachlor (26) is described in detail elsewhere (Chapters 12 and 15). This compound is sold as an enantio-enriched compound ( 80% ee) rather than the pure enantiomer because of economic constraints. Metolachlor (26) is a pesticide sold since March 1997 as the enantiomerically enriched form and sold under the trade name DUAL MAGNUM .242 244 Since its... 

With the exception of S-metolachlor, all the molecules listed under the column Final Target are used in pharmaceutical formulations. Dilitiazem is a Ca2+ antagonist, while Cilazapril is an angiotensin-converting enzyme inhibitor. Levofloxacin is an antibacterial, and cilastatin is used as an in vivo stabilizer of the antibiotic imipenem. S-metolachlor is a herbicide sold under the trade name of DUAL MAGNUM. Although the structures of the final targets are more complex than those of the intermediates, enantioselective syntheses of the intermediates are the most crucial steps in the complex synthetic schemes of these molecules. 

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... 

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. 

Nowadays enantioselective synthesis of the herbicide (5)-metolachlor (Dual Magnum) is, to our knowledge, one of the most successful commercial applications of asymmetric C=N bond hydrogenation. Developed by Blaser and Spindler as a key step in the technical synthesis of (5)-metolachlor, the enantioselective hydrogenation of an imine intermediate 193 proceeds in the presence of an iridium ferrocenyl-diphosphine catalyst bearing a Solvias Josiphos-type chiral ligand (/ )-Xyliphos to give... 

A combination of metolachlor (Dual ) and atrazine in a liquid prepack called Bicep facilitated the growing practice of mixing atrazine with grass herbicides. Test marketed in 1978 and 1979, Bicep was introduced nationally in 1980. In 1997, atrazine was combined with S-metolachlor to produce Bicep II Magnum , since. S -metolachlor contains more of the active isomer and reduces the amount of herbicide needed for efficacy. 

S-metolachlor is also the active ingredient in Dual II Magnum (Syngenta). This product also contains a safener, benoxacor. Safener is a name for compounds that protect crops from herbicide injury without replacing herbicide activity in targeted weeds. Various chemicals have been developed to act... 

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