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BINOL-Based Ditopic Diphosphite Ligands – Synthesis, Evaluation and Regioselectivity Optimization of Catalytic Hydroformylation by 23 Factorial Design

[ Vol. 11 , Issue. 2 ]

Author(s):

Andreia F. Peixoto, Artur R. Abreu, Ana R. Almeida, Angela Neves, Paulo E. Abreu, Maria J.S.M. Moreno, Juan C. Bayon, Alberto A.C.C. Pais and Mariette M. Pereira   Pages 301 - 309 ( 9 )

Abstract:


BINOL-based diphosphite ligands containing oxygen or nitrogen heteroatoms are currently a new class of promising ligands for homogeneous catalysis. Herein we present a useful strategy to synthesize ditopic (R)-BINOL-based diphosphites, containing pyridyl or propyl ether bridges between BINOL fragments in high isolated yields (50-92 %). Their rhodium complexes were evaluated in styrene hydroformylation, in which a moderate regioselectivity for the branched aldehyde was observed. The addition of a lithium salt led to a significant increase in the regioselectivity (25 %) for the branched aldehyde. This interesting observation has been rationalized based on a full two-level factorial design with 3 factors, including pressure, temperature and the Li/Rh ratio, using Rh/10 as model catalyst. The improvement of the regioselectivity in the presence of lithium salts has been interpreted through31PNMR spectroscopy and semiempirical PM6 computational studies.

Keywords:

BINOL, diphosphite, ditopic, hydroformylation, rhodium, regioselectivity, Lithium ion.

Affiliation:

Centro de Química de Coimbra, Departmento de Química, Universidade de Coimbra, Rua Larga, 3030-535 Coimbra, Portugal.

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