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Helicene‐Based Phosphite Ligands in Asymmetric Transition‐Metal Catalysis: Exploring Rh‐Catalyzed Hydroformylation and Ir‐Catalyzed Allylic Amination
Author(s) -
Krausová Zuzana,
Sehnal Petr,
Bondzic Bojan P.,
Chercheja Serghei,
Eilbracht Peter,
Stará Irena G.,
Šaman David,
Starý Ivo
Publication year - 2011
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201100259
Subject(s) - hydroformylation , chemistry , helicene , amination , allylic rearrangement , regioselectivity , enantioselective synthesis , medicinal chemistry , catalysis , ligand (biochemistry) , stereochemistry , rhodium , organic chemistry , molecule , biochemistry , receptor
Starting from the optically pure [6]helicene‐like alcohol( P ,3 S )‐3‐methyl‐4‐(4‐methylphenyl)‐1,3,6,7‐tetrahydrobenzo[ c ]benzo[5,6]phenanthro[4,3‐ e ]oxepin‐14‐ol, four helical phosphites were prepared from the corresponding chlorophosphites. These ligands containing parent or substituted 1,3,2‐dioxaphospholan‐2‐yl or dibenzo[ d , f ][1,3,2]dioxaphosphepin‐6‐yl moieties were applied to the asymmetric hydroformylation of terminal alkenes catalyzed by Rh(acac)(CO) 2 and the asymmetric allylic amination of cinnamyl‐type carbonates catalyzed by [Ir(cod)Cl] 2 . The helical phosphite containing the dibenzo[ d , f ][1,3,2]dioxaphosphepin‐6‐yl group was most successful in the asymmetric hydroformylation of styrene, leading to moderate enantiomeric excess values (up to 32 % ee ), high regioselectivity in favor of the branched product, and mostly high conversion, whereas the helical ligand containing the 4,4,5,5‐tetramethyl‐1,3,2‐dioxaphospholan‐2‐yl fragment was most effective in asymmetric allylic aminations, exhibiting high enantioselectivity (up to 94 % ee ), excellent regioselectivity in favor of the branched products, and good reactivity. This study represents the first use of helicene‐like ligands in asymmetric reactions, including hydroformylation and allylic amination, and the promising results indicate the potential of the helicene moieties as chiral inductors.