Premium
Synthesis of Recyclable Fluorous Chiral Ligands and Evaluation of Their Catalytic Activity toward Asymmetric Addition of Dimethylzinc to Aldehydes
Author(s) -
Sokeirik Yasser S.,
Hoshina Akiko,
Omote Masaaki,
Sato Kazuyuki,
Tarui Atsushi,
Kumadaki Itsumaro,
Ando Akira
Publication year - 2008
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.200800188
Subject(s) - chemistry , cyclohexanone , ligand (biochemistry) , acetone , aldehyde , enantiomer , chiral ligand , solvent , solubility , organic chemistry , enantioselective synthesis , asymmetric induction , tris , catalysis , medicinal chemistry , biochemistry , receptor
The asymmetric addition of Me 2 Zn to aldehydes is very slow and mostly gives low ee values. Previously, we reported the synthesis of a fluorous chiral ligand, (4 R ,5 S ,α′ R )‐2,2‐dimethyl‐α,α,α′‐tris(perfluorooctyl)‐2,3‐dioxolane‐4,5‐dimethanol ( 1 a ), derived from tartarate as a chiral pool. Ligand 1 a showed high activity toward the addition of Me 2 Zn to aldehydes with high enantiomeric excess. However, the very high content of fluorine makes 1 a difficult to dissolve in common solvents; hence, much solvent is required, which limits its use. This report describes the modification of 1 a by replacing either the perfluorooctyl groups with shorter perfluoroalkyl ones or the acetone ketal part with cyclohexanone ketal. The perfluorobutyl analogue 1 c is much more soluble than 1 a and shows comparable asymmetric induction toward the addition of Me 2 Zn to aldehydes. Furthermore, 1 c has a much lower molecular weight than 1 a . This means that 1 c is used in smaller amounts (weight) than 1 a . The cyclohexanone ketal analogue 1 d is more soluble than 1 a and more easily synthesized owing to its high solubility and ease of crystallization. Ligand 1 d showed much higher asymmetric induction toward cyclohexanecarbaldehyde, a branched aldehyde, than 1 a . Thus, 1 a was modified into ligands with higher performance.