title: Reversal of enantioselectivity in the hydroformylation of styrene with [2S,4S-BDPP]Pt(SnCl3)Cl at high temperature arises from a change in the enantioselective-determining step.
abstract: Deuterioformylation of styrene catalyzed by [(2S,4S)-BDPP]Pt(SnCl(3))Cl at 39 degrees C gave 3-phenylpropanal (3) and 2-phenylpropanal (2) (n:i = 1.8, 71% ee (S)-2) with deuterium only beta to the aldehyde carbonyl and in the formyl group. Small amounts of deuterium were also found in the internal (2.8%), cis terminal (1.4%), and trans terminal (1.3%) vinyl positions of the recovered styrene. Deuterioformylation of styrene at 98 degrees C gave 3- (3) and 2-phenylpropanal (2) (n:i = 2.3, 10% ee (R)-2) with deuterium both alpha and beta to the aldehyde carbonyl and in the formyl group. Deuterium was also found in the internal (20%), cis terminal (12%), and trans terminal (12%) vinyl positions of the recovered styrene. These deuterioformylation results establish that platinum hydride addition to styrene is largely irreversible at 39 degrees C but reversible at 98 degrees C. Hydroformylation of (E)- and (Z)-beta-deuteriostyrene at 40 degrees C, followed by oxidation of the aldehydes to acids, and subsequent derivitization to the (S)-mandelate esters confirmed that 84% of 2-phenylpropanal (2) arises from platinum hydride addition to the si-face of styrene, while 73% of 3-phenylpropanal (3) arises from platinum hydride addition to the re-face of styrene. At 100 degrees C, the effect of variable H(2) and CO pressure on n:i, % ee, and TOF of hydroformylation of styrene was investigated. The results are consistent with enantioselectivity not being fully determined until the final hydrogenolysis of a platinum acyl intermediate.
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA. casey@chem.wisc.edu
authors.forename: Charles P
authors.initials: CP
authors.lastname: Casey
authors.forename: Susie C
authors.initials: SC
authors.lastname: Martins
authors.forename: Maureen A
authors.initials: MA
authors.lastname: Fagan
mesh_terms: D000447:Aldehydes / Q000737:chemistry; D002248:Carbon Monoxide / Q000737:chemistry; D002384:Catalysis; D003903:Deuterium / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009944:Organoplatinum Compounds / Q000737:chemistry*; D009947:Organotin Compounds / Q000737:chemistry*; D011312:Pressure; D020005:Propanols; D013237:Stereoisomerism; D020058:Styrene / Q000737:chemistry*; D013696:Temperature
chemical_list: C488520:(2,4-bis(diphenylphosphino)pentane)platinum(trichlorotin) chloride; D000447:Aldehydes; D009944:Organoplatinum Compounds; D009947:Organotin Compounds; D020005:Propanols; C439395:1-phenylpropanol; D020058:Styrene; D002248:Carbon Monoxide; D006859:Hydrogen; D003903:Deuterium