Modular chiral diphosphite derived from l-tartaric acid. Applications in metal-catalyzed asymmetric reactions

Alonso Rosas-Hernández, Edgar Vargas-Malvaez, Erika Martin, Laura Crespi, J. Carles Bayón

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11 Citations (Scopus)

Abstract

A new family of C2-symmetric chiral diphosphites was synthesized using two different chiral backbones derived from tartaric acid, combined with chiral binaphthyls or non-chiral substituted biphenyl moieties. Diphosphites were applied to Rh-catalyzed hydroformylation of styrene producing good conversions in mild conditions, fair regioselectivities but low enantioselectivities in all cases. Ligands were also essayed in Pd-catalyzed allylic substitution reactions of linear and cyclic substrates using dimethyl malonate as nucleophile. Conversion rates up to 7200 h-1 were reached, while moderated ee's were attained. In this reaction, a kinetic resolution of rac-1,3-diphenyl-3-acetoxyprop-1-ene was observed, leading to 99% ee of for the unreacted S-substrate and 60% ee of S-alkylated product. Coordination properties of diphosphites in rhodium and palladium complexes related to catalytic species involved in the two previous reactions were investigated. Some ligands form equatorial-equatorial chelates in pentacoordinated complexes [RhH(CO)(PPh3)(diphosphite)], while other act as bridge between two metal atoms. In the catalytic active species [Pd(η3-PhCHCHCHPh)(diphosphite)]PF6 one or two diastereoisomers are formed, depending on the diphosphite structure. © 2010 Elsevier B.V.
Original languageEnglish
Pages (from-to)68-75
JournalJournal of Molecular Catalysis A: Chemical
Volume328
Issue number1-2
DOIs
Publication statusPublished - 3 Aug 2010

Keywords

  • Allylic alkylation
  • Asymmetric catalysis
  • Chiral diphosphite
  • Hydroformylation

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