title: Bis-(2,5-diphenylphospholanes) with sp2 carbon linkers: synthesis and application in asymmetric hydrogenation.
abstract: 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.
authors.affiliation: 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
authors.forename: Martin E
authors.initials: ME
authors.lastname: Fox
authors.forename: Mark
authors.initials: M
authors.lastname: Jackson
authors.forename: Ian C
authors.initials: IC
authors.lastname: Lennon
authors.forename: Jerzy
authors.initials: J
authors.lastname: Klosin
authors.forename: Khalil A
authors.initials: KA
authors.lastname: Abboud
mesh_terms: 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
chemical_list: 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