TY - JOUR
T1 - Successful application of a “forgotten” phosphine in asymmetric catalysis
T2 - A 9-phosphabicyclo[3.3.1]non-9-yl ferrocene derivative as chiral ligand
AU - Abbenhuis, Hendrikus C.L.
AU - Burckhardt, Urs
AU - Gramlich, Volker
AU - Köllner, Christoph
AU - Pregosin, Paul S.
AU - Salzmann, Renzo
AU - Togni, Antonio
PY - 1995/1/1
Y1 - 1995/1/1
N2 - The technical mixture phobane”, containing the two isomers 9-phospha-9H-bicyclo[3.3.1]-nonane (3a) and 9-phospha-9H-bicyclo[4.2.1]nonane (3b) in a ~2:1 ratio was reacted with N,N-dimethyl-(S)-l-[(R)-2-(diphenylphosphino)ferrocenyl]ethylamine (4) in acetic acid. The clean amine substitution product is the new chiral biphosphine 5. When only 2 equiv of 3 were reacted with 4, a 4:1 mixture of the two isomeric products 5a and 5b were obtained. However, the use of a 10-fold excess of 3 afforded the pure [3.3.1]-isomer 5a, 9-phospha-9-[(S)-l-{(R)-2-(diphenylphosphino)ferrocenyl}ethyl][3.3.1]bicyclononane, in 68% isolated yield. (S)-(R)-5a crystallizes in the orthorhombic space group P212121, Z = 4, α = 7.393(3) Å, b = 19.261(5) Å, and c = 19.546(8) Å. 5a was used in the asymmetric Pd-catalyzed alkylation of l,3-diphenyl-3-acetoxypropene with dimethyl malonate. Enantioselectivities up to 85% ee were obtained. The cationic Pd—allyl complexes [Pd(η3-C3H5)(5a)]O3SCF3(6) and [Pd(η3-PhCHCHCHPh)(5a)]O3SCF3 (7) were prepared and characterized by X-ray diffraction. Complex 6 crystallizes in the monoclinic space group P21, Z = 2, α = 9.162(4) Å, b = 16.069-(5) Å, c = 11.816(5) Å, and β = 96.86(3)°. Crystalline 7 was obtained as a CH2Cl2 monosolvate and belongs to the triclinic system: space group P1, Z = 1, a = 11.07(2) Å, b = 11.216(14) Å, c = 11.888(16) Å, a = 62.37(9)°, β = 65.96(11)°, and γ = 70.29(11)°. The ligand assumes very different conformations in its complexes, as compared to the free state. Multidimensional 31P, 13C, and 1H NMR studies reveal that 7 exists in solution as a mixture of four isomers. Aspects of the selective equilibria were elucidated using 31P- and 1H-exchange spectroscopy.
AB - The technical mixture phobane”, containing the two isomers 9-phospha-9H-bicyclo[3.3.1]-nonane (3a) and 9-phospha-9H-bicyclo[4.2.1]nonane (3b) in a ~2:1 ratio was reacted with N,N-dimethyl-(S)-l-[(R)-2-(diphenylphosphino)ferrocenyl]ethylamine (4) in acetic acid. The clean amine substitution product is the new chiral biphosphine 5. When only 2 equiv of 3 were reacted with 4, a 4:1 mixture of the two isomeric products 5a and 5b were obtained. However, the use of a 10-fold excess of 3 afforded the pure [3.3.1]-isomer 5a, 9-phospha-9-[(S)-l-{(R)-2-(diphenylphosphino)ferrocenyl}ethyl][3.3.1]bicyclononane, in 68% isolated yield. (S)-(R)-5a crystallizes in the orthorhombic space group P212121, Z = 4, α = 7.393(3) Å, b = 19.261(5) Å, and c = 19.546(8) Å. 5a was used in the asymmetric Pd-catalyzed alkylation of l,3-diphenyl-3-acetoxypropene with dimethyl malonate. Enantioselectivities up to 85% ee were obtained. The cationic Pd—allyl complexes [Pd(η3-C3H5)(5a)]O3SCF3(6) and [Pd(η3-PhCHCHCHPh)(5a)]O3SCF3 (7) were prepared and characterized by X-ray diffraction. Complex 6 crystallizes in the monoclinic space group P21, Z = 2, α = 9.162(4) Å, b = 16.069-(5) Å, c = 11.816(5) Å, and β = 96.86(3)°. Crystalline 7 was obtained as a CH2Cl2 monosolvate and belongs to the triclinic system: space group P1, Z = 1, a = 11.07(2) Å, b = 11.216(14) Å, c = 11.888(16) Å, a = 62.37(9)°, β = 65.96(11)°, and γ = 70.29(11)°. The ligand assumes very different conformations in its complexes, as compared to the free state. Multidimensional 31P, 13C, and 1H NMR studies reveal that 7 exists in solution as a mixture of four isomers. Aspects of the selective equilibria were elucidated using 31P- and 1H-exchange spectroscopy.
UR - http://www.scopus.com/inward/record.url?scp=0000706939&partnerID=8YFLogxK
U2 - 10.1021/om00002a025
DO - 10.1021/om00002a025
M3 - Article
AN - SCOPUS:0000706939
VL - 14
SP - 759
EP - 766
JO - Organometallics
JF - Organometallics
SN - 0276-7333
IS - 2
ER -