136776-57-3Relevant articles and documents
Hydrogenation of Acrylic Acids catalysed by Complexes of Rhodium(I) containing Mixed Anhydrides of Acrylic and Diphenylphosphinous Acids
Iraqi, Ahmed,Fairfax, Neil R.,Preston, Sheila A.,Cupertino, Domenico C.,Irvine, Derek J.,Cole-Hamilton, David J.
, p. 1929 - 1936 (2007/10/02)
Complexes of the form n(Ph2PO2CCR=CR'R")> (n = 1 or 2) or PF6 (R, R', R" = H, alkyl or aryl) have been shown to be more effective for the catalytic hydrogenation of acrylic acids in the presence of added base (KOH or NEt3) than is .Mechanistic studies show that the active species is , in which the mixed anhydride is bound through both the phosphorus atom and the double bond.After hydrogenation of the double bond of the mixed anhydride, new substrate is introduced by a base-catalysed transesterification reaction at the phosphorus atom of the mixed anhydride.This is modelled in the reactions of , which exists in two isomeric forms, one with binding of the mixed anhydride only through P and the other with binding of the mixed anhydride through P and O, or of PF6 with MeCH=CHCO2-, which give in high yield.Hydrogenation of hexa-2,4-dienoic acid gives hex-4-enoic acid and hexanoic acid and evidence is presented that these two products are obtained from hydrogenation of the mixed anhydride (hex-4-enoic acid as product) or of the directly bonded anion (hexanoic acid as product).Attempts to promote high enantioselectivity in the hydrogenation of PhC=CMeCO2H by using *)(Ph2PO2CCMe=CHPh)>PF6 (P-P* = a chiral diphosphine) were frustrated by the displacement of the mixed anhydride and the formation of *)(Ph2POPPh2)>PF6.Enantiomeric excesses of only ca. 10percent were achieved.
