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Chiral Bicyclic Phosphoramidites—A New Class of Ligands for Asymmetric Catalysis
Author(s) -
Huttenloch Oliver,
Spieler Jan,
Waldmann Herbert
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010202)7:3<671::aid-chem671>3.0.co;2-m
Subject(s) - bicyclic molecule , class (philosophy) , chemistry , combinatorial chemistry , stereochemistry , catalysis , organic chemistry , computer science , artificial intelligence
The development of new ligands for catalytic asymmetric C−C bond formation is of great interest to organic synthesis. We describe here a new class of chiral phosphoramidites that embody one or two binaphthol units attached to an achiral azabicyclic [3.3.1] or [3.3.0] framework. These ligands were easily accessible from ( R )‐1,1′‐binaphthyl‐2,2′‐dioxaphosphorchloridite ( 4 ) and the corresponding heterobicyclic core 1, 2 , or 3 . They were employed in enantioselective Cu‐catalyzed additions of different dialkylzinc reagents to cyclic and acyclic enones. The chiral ketones were obtained with an enantiomeric ratio up to 91:9. The choice of the best ligand proved to be strongly dependent on each substrate. In addition, ligand 6 was found to be the most suitable for Rh‐catalyzed hydrogenations of α , β ‐unsaturated esters, giving rise to dimethyl 2‐methylsuccinate and methyl N ‐acetylalaninate with enantiomer ratios up to 95:5.