Influence of the 4-substituents on the reversal of enantioselectivity in the asymmetric hydroformylation of 4-substituted styrenes with PtCl(SnCl 3)[(2 S, 4 S)-BDPP]

Péter Pongrácz, Tamara Papp, László Kollár, Tamás Kégl

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Abstract

The enantioselectivity of the asymmetric hydroformylation of 4-substituted styrenes in the presence of an in situ catalyst, formed from PtCl(SnCl 3)[(2S,4S)-BDPP] and tin(II) chloride, was influenced by the reaction temperature. The preferred formation of the S and the R enantiomers of the branched aldehyde regioisomers (2a-g) was observed at low and high temperatures, respectively. The electron-donor or electron-acceptor properties of the para substituents of styrene show correlation with the changes in enantioselectivity, especially with the reversal temperature of the enantioselectivity. The reversibility of the formation of the Pt-branched alkyl intermediates, leading to the corresponding R and S enantiomers of 2-arylpropanals, depends on the Hammett constants. The electronic effect of para substituents was investigated by quantum chemical methods employing the simple olefin adducts [HPt(PH 3)2(olefin)(SnCl3)]. Excellent linear correlation was found between the para substituent constants and the electrostatic potential at nuclei of the platinum atom. Equally good correlation has been established for the other atoms as well in the coordination sphere of Pt.

Original languageEnglish
Pages (from-to)1389-1396
Number of pages8
JournalOrganometallics
Volume33
Issue number6
DOIs
Publication statusPublished - Mar 24 2014

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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