title: Synthesis of recyclable fluorous chiral ligands and evaluation of their catalytic activity toward asymmetric addition of dimethylzinc to aldehydes.
abstract: 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, (4R,5S,alpha'R)-2,2-dimethyl-alpha,alpha,alpha'-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.
authors: Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Japan.
authors: Yasser S
authors: YS
authors: Sokeirik
authors: Akiko
authors: A
authors: Hoshina
authors: Masaaki
authors: M
authors: Omote
authors: Kazuyuki
authors: K
authors: Sato
authors: Atsushi
authors: A
authors: Tarui
authors: Itsumaro
authors: I
authors: Kumadaki
authors: Akira
authors: A
authors: Ando
mesh_terms: D000447:Aldehydes / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D004148:Dioxolanes / Q000737:chemistry; D005461:Fluorine / Q000737:chemistry*; D005466:Fluorocarbons / Q000737:chemistry; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: C533059:(4R,5S,alpha'R)-2,2-dimethyl-alpha,alpha,alpha'-tris(perfluorooctyl)-2,3-dioxolane-4,5-dimethanol; D000447:Aldehydes; D004148:Dioxolanes; D005466:Fluorocarbons; D008024:Ligands; D009942:Organometallic Compounds; D005461:Fluorine; C511262:dimethylzinc