219505-52-9Relevant academic research and scientific papers
Iridium complexes with new 1,2-dithioether chiral ligands containing a rigid cyclic backbone. Application in homogeneous catalytic asymmetric hydrogenation
Dieguez, Montserrat,Ruiz, Aurora,Claver, Carmen,Pereira, Maria M.,Rocha Gonsalves, Antonio M. D'A.
, p. 3517 - 3522 (2007/10/03)
New chiral dithioether compounds (-)-1-benzyl-3,4-bis(methylsulfanyl)pyrrolidine (-)-degusme, (-)-1-benzyl-3,4-bis(isopropylsulfanyl)pyrrolidine (-)-deguspri and (+)-1-benzyl-3,4-bis(phenylsulfanyl)pyrrolidine (+)-degusph were prepared from (+)-L-tartaric acid. The addition of the dithioether compounds to a dichloromethane solution of [Ir(cod)2]BF4 afforded the chiral cationic complexes [Ir(cod){(-)-degusme}]BF4 1 [Ir(cod){(-)-deguspri}]BF4·CH2Cl 2 2 and [Ir(cod){(+)-degusph}]BF4 3. The dithioether ligands were replaced by PPh3 in complexes 1, 2 and 3 providing the [Ir(cod)(PPh3)2]BF4 complex. The addition of H2 to 1, 2 and 3 at -70°C gave cis-dihydridoiridium(III) complexes [IrH2(cod)L]BF4 [L = (-)-degusme 4, (-)-deguspri 5 or (+)-degusph 6]. The relative stability of possible isomers for complexes 1-6 was studied by molecular mechanics calculations. Complexes 1-3 were active precursors in the asymmetric hydrogenation of different prochiral dehydroamino acid derivatives and itaconic acid, at room temperature under atmospheric pressure of H2, and the highest enantiomeric excess obtained was 68%.
