ENANTIOSELECTIVE CATALYSIS FOR AGROCHEMICALS - SYNTHETIC ROUTES TO (S)-METOLACHLOR, (R)-METALAXYL AND (ALPHA-S,3R)-CLOZYLACON

The application of enantioselective catalytic methods for the technica l preparation of chiral agrochemicals is illustrated for three active ingredients of the acylanilide type. The key step for the technical sy nthesis of the herbicide (S)-metolachlor is the enantioselective hydro genation of an imine intermediate using a novel iridium ferrocenyldiph osphine catalyst with an unprecedented high activity and 80% ee. (R)-m etalasyl and (alpha S,3R)-clozylacon were synthesized via the enantios elective hydrogenation of corresponding enamide precursors with Rh and Ru/binap catalysts with >95% and 99% enantiomeric purity, respectivel y. (C) 1998 Society of Chemical Industr.