NOVEL CHIRAL LIGANDS, DIFERROCENYL DICHALCOGENIDES AND THEIR DERIVATIVES, FOR RHODIUM-CATALYZED AND IRIDIUM-CATALYZED ASYMMETRIC HYDROSILYLATION

Citation
Y. Nishibayashi et al., NOVEL CHIRAL LIGANDS, DIFERROCENYL DICHALCOGENIDES AND THEIR DERIVATIVES, FOR RHODIUM-CATALYZED AND IRIDIUM-CATALYZED ASYMMETRIC HYDROSILYLATION, Organometallics, 15(1), 1996, pp. 370-379
Citations number
50
Categorie Soggetti
Chemistry Inorganic & Nuclear","Chemistry Inorganic & Nuclear
Journal title
ISSN journal
02767333
Volume
15
Issue
1
Year of publication
1996
Pages
370 - 379
Database
ISI
SICI code
0276-7333(1996)15:1<370:NCLDDA>2.0.ZU;2-7
Abstract
As chiral ligands for transition metal complex-catalyzed asymmetric re actions, a variety of novel chiral ferrocenyl chalcogen compounds, whi ch possess planar chirality due to the 1,2-unsymmetrically disubstitut ed ferrocene structure, have been prepared from chiral ferrocenes. The re are seven diferrocenyl dichalcogenides (4-10), nine alkyl or aryl f errocenyl chalcogenides (11-19), two bis(ferrocenylseleno)alkanes (20 and 21), two cogeno)-1-[2-(diphenylphosphino)ferrocenyl]ethanes (22 an d 24), and two )-1-[1',2-bis(diphenylphosphino)ferrocenyl]ethanes (23 and 25). ene-2,3-dihydroxy-1,4-bis(phenylchalcogeno)butanes (26-28) ar e also synthesized. The Rh(I) complex-catalyzed hydrosilylation of ket ones with diphenylsilane in the presence of these chiral ligands inclu ding the reported [1-(dimethylamino)ethyl]ferrocenyl]dichalcogenides ( 1-3), followed by hydrolysis with dilute HCl, affords the correspondin g chiral alcohols (R-configuration) in moderate to quantitative yield with up to 88% enantiomeric excess (ee), Similar treatment of acetophe none in the presence of diferrocenyl dichalcogenides (1, 2, 3, and 10) and a catalytic amount of Ir(I) complex gives chiral 1-phenylethanol of the opposite configuration (S) compared with the Rh case in high yi eld with up to 23% ee. The new complex prepared from a cationic rhodiu m compound and the diferrocenyl diselenide (2) shows an activity for a symmetric hydrosilylation of acetophenone to afford 1-phenylethanol in 60% chemical yield with 60% ee. Asymmetric hydrosilylation of imines and asymmetric hydrogenation of an enamide also proceed smoothly using the Rh(I)-diselenide (2) catalytic system to give the corresponding s ec-amines and amide with up to 53% and 69% ee, respectively. A catalyt ic cycle involving the formation of tetracoordinated rhodium(I)-dichal cogenide complex (two Se and two N atoms to one Rh) followed by oxidat ive addition of the Si-H bond to Rh(I) and carbonyl addition to the pr oduced rhodium(III) hydride complex is proposed for hydrosilylation of ketones.