New homochiral ligands bearing nonstereogenic chirotopic centers. lithiated N, N'-dialkylureas as chiral bases and sterically crowded phosphines for asymmetric …

…, C Malan, K Harms, P Knochel

Index: Graf, Claus-Dieter; Malan, Christophe; Harms, Klaus; Knochel, Paul Journal of Organic Chemistry, 1999 , vol. 64, # 15 p. 5581 - 5588

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Citation Number: 37

Abstract

The synthesis of new homochiral pseudo-C 2-symmetrical ligands of type 1 bearing a nonstereogenic chirotopic center is reported. Two such structural units are combined in the ureas 2 and 10, which proved to be useful for enantioselective deprotonation and alkylation of ketones (up to 88% ee). The monophosphine 3 induced a high enantiomeric excess in the Pd-catalyzed allylation of dimethyl malonate (up to 73% ee). Furthermore, we have shown ...