Bis-(2,5-diphenylphospholanes) with sp2 carbon linkers: synthesis and application in asymmetric hydrogenation.
Four chiral diphosphine ligands consisting of bis(2,5-diphenylphospholan-1-yl) groups connected by the sp(2) carbon linkers 2,3-quinoxaline ((S,S)-Ph-Quinox), 2,3-pyrazine ((S,S)-Ph-Pyrazine), maleic anhydride ((S,S)-Ph-MalPhos), and 1,1'-ferrocene ((S,S)-Ph-5-Fc) were synthesized, and their cationic [rhodium(I)(COD)] complexes were prepared. These complexes were tested in asymmetric hydrogenation of functionalized olefins. [((S,S)-Ph-Quinox)Rh(COD)]BF4 showed high activity and selectivity against itaconate and dehydroamino acid substrates. The corresponding (S,S)-Ph-Pyrazine and (S,S)-Ph-MalPhos complexes exhibited lower activities and selectivities. [((S,S)-Ph-5-Fc)Rh(COD)]BF4 showed high activity with low selectivity for these substrates, but high activity and selectivity against 2-C-substituted cinnamate salts, whereas rhodium complexes of (S,S)-Ph-Quinox and (R,R)-Ph-BPE showed low activity and selectivity against 2-C-substituted cinnamate salts.
Fox
Martin E
ME
Dowpharma, Chirotech Technology Ltd, a subsidiary of The Dow Chemical Company, Unit 162 Cambridge Science Park, Milton Road, Cambridge, CB4 0GH, UK. Mfox@dow.com
Jackson
Mark
M
Lennon
Ian C
IC
Klosin
Jerzy
J
Abboud
Khalil A
KA
D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D002934:Cinnamates / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry*; D006865:Hydrogenation; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008299:Maleic Anhydrides / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D019800:Phenol / Q000138:chemical synthesis / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry*; D011719:Pyrazines / Q000737:chemistry; D011810:Quinoxalines / Q000737:chemistry; D012238:Rhodium / Q000737:chemistry; D013237:Stereoisomerism; D013386:Succinates / Q000737:chemistry
D002934:Cinnamates; D003432:Cross-Linking Reagents; D008024:Ligands; D008299:Maleic Anhydrides; D011719:Pyrazines; D011810:Quinoxalines; D013386:Succinates; C029010:cinnamic acid; D010758:Phosphorus; D019800:Phenol; D002244:Carbon; D012238:Rhodium; C005229:itaconic acid