Screening of amino sulfur ferrocenes as catalysts for the enantioselective addition of diethylzinc to benzaldehyde

Seventeen amino-sulfoxides and sulfides incorporating a ferrocene backbone were prepared in enantiopure form and tested as ligands for the asymmetric addition of diethylzinc to benzaldehyde. They all exhibited catalytic activity. Fine tuning of substituents, the nature of the sulfur functionality, and configurations with a synergy of planar and central chiralities allowed us to reach an enantiomeric excess of 90%.

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