10.1021/jo990412u.s001
Claus-Dieter Graf
Claus-Dieter
Graf
Christophe Malan
Christophe
Malan
Klaus Harms
Klaus
Harms
Paul Knochel
Paul
Knochel
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
American Chemical Society
1999
ureas 2
ee
C 2
monophosphine 3
Chiral Bases
Lithiated N
ligand
ketone
New Homochiral Ligands Bearing Nonstereogenic Chirotopic Centers
nonstereogenic chirotopic center
achiral sterically
enantiomeric
type 1
alkylation
synthesis
alkyl diphosphine 23
allylation
Sterically Crowded Phosphines
dimethyl malonate
Dialkylurea
Asymmetric Catalysis
homochiral
enantioselective deprotonation
Pd
1999-06-24 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/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/3718164
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.