New Homochiral Ligands Bearing Nonstereogenic Chirotopic Centers. Lithiated <i>N</i>,<i>N</i><i>‘</i>-Dialkylureas as Chiral Bases and Sterically Crowded Phosphines for Asymmetric Catalysis GrafClaus-Dieter MalanChristophe HarmsKlaus KnochelPaul 1999 The synthesis of new homochiral pseudo-<i>C</i><i><sub>2</sub></i>-symmetrical ligands of type <b>1</b> bearing a nonstereogenic chirotopic center is reported. Two such structural units are combined in the ureas <b>2</b> and <b>10</b>, which proved to be useful for enantioselective deprotonation and alkylation of ketones (up to 88% <i>ee</i>). The monophosphine <b>3</b> induced a high enantiomeric excess in the Pd-catalyzed allylation of dimethyl malonate (up to 73% <i>ee</i>). Furthermore, we have shown that the achiral sterically crowded alkyl diphosphine <b>23</b> efficiently stabilized Pd(0) at high temperatures.