title: Synthesis and application of a new bisphosphite ligand collection for asymmetric hydroformylation of allyl cyanide.
abstract: A series of mono- and bidentate phosphites was prepared with (S)-5,5',6,6'-tetramethyl-3,3'-di-tert-butyl-1,1'-biphenyl-2,2'-dioxy [(S)-BIPHEN] as a chiral auxiliary and screened in the asymmetric hydroformylation of allyl cyanide. These hydroformylation results were compared with those of two existing chiral ligands, Chiraphite and BINAPHOS, whose utility in asymmetric hydroformylation has been previously demonstrated. Bisphosphite 11 with a 2,2'-biphenol bridge was found to be the best overall ligand for asymmetric hydroformylation of allyl cyanide with up to 80% ee and regioselectivities (branch-to-linear ratio, b/l) of 20 with turnover frequency of 625 [h(-)(1)] at 35 degrees C. BINAPHOS gave enantioselectivities up to 77% ee when the reaction was conducted in either acetone or neat but with poor regioselectivity (b/l 2.8) and activities 7 times lower than that of 11. The product of allyl cyanide hydroformylation using (R,R)-11 was subsequently transformed into (R)-2-methyl-4-aminobutanol, a useful chiral building block. Single-crystal X-ray structures of (S,S)-11 and its rhodium complex 19 were determined.
authors.affiliation: Dowpharma, Chirotech Technology Limited, a subsidiary of The Dow Chemical Company, 321 Cambridge Science Park, Cambridge CB4 0WG, UK.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Cobley
authors.forename: Kelli
authors.initials: K
authors.lastname: Gardner
authors.forename: Jerzy
authors.initials: J
authors.lastname: Klosin
authors.forename: Céline
authors.initials: C
authors.lastname: Praquin
authors.forename: Catherine
authors.initials: C
authors.lastname: Hill
authors.forename: Gregory T
authors.initials: GT
authors.lastname: Whiteker
authors.forename: Antonio
authors.initials: A
authors.lastname: Zanotti-Gerosa
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Petersen
authors.forename: Khalil A
authors.initials: KA
authors.lastname: Abboud