Ulrich Pittelkow

The heterogeneous enantioselective hydrodehalogenation of α,α-dichlorobenzazepinone-2: A unique case of substrate specificity.

Abstract The enantioselective hydrodehalogenation of α,α-dichlorobenzazepinone-2 with cinchona modified Pd- and Pt-catalysts was investigated using a random screening approach. The effect of important reaction parameters was determined and optimized. The best optical yields (50% ee) were obtained with a 5% Pd/BaSO 4 catalyst modified with cinchonine in THF with NBu 3 as HCl acceptor. Very high modifier and catalyst concentrations were necessary to get good optical yields and reasonable rates because the modifier decreases the catalyst activity. The absolute configuration of α-chlorobenzazepinone-2 was determined. Attempts to extend this enantioselective dehalogenation reaction to other α,α-dihalogen substituted acid derivatives were unsuccessful.

Enantioselective catalysis for agrochemicals: Synthetic routes to (S)-metolachlor, (R)-metalaxyl and (αS, 3R)-clozylacon

The application of enantioselective catalytic methods for the technical preparation of chiral agrochemicals is illustrated for three active ingredients of the acylanilide type. The key step for the technical synthesis of the herbicide (S)-metolachlor is the enantioselective hydrogenation of an imine intermediate using a novel iridium ferrocenyldiphosphine catalyst with an unprecedented high activity and 80% ee. (R)-metalaxyl and (αS,3R)-clozylacon were synthesized via the enantioselective hydrogenation of corre-sponding enamide precursors with Rh and Ru/binap catalysts with >95% and 99% enantiomeric purity, respectively.