Molecular Modelling: Ein Beitrag zum Verständnis der katalytischen enantioselektiven Hydrovinylierung von Styrol / Molecular Modelling: A Contribution to the Understanding of the Catalytic Enantioselective Hydrovinylation of Styrene

Abstract

The hydrovinylation of styrene can be catalyzed by the addition of phosphane-modified Ni(II) compounds with high reactivity and enantioselectivity if the azaphospholene 1 is used as P-component of the catalysts. Until recently the industrial applications of 1 have been hampered by its difficult synthesis. To search for easier to synthesize, but equally well catalyzing derivatives of 1 a molecular modelling study was carried out. Based on already experimentally tested and structurally characterized azaphospholenes a model is developed, which not only leads to a better understanding of the catalytic process and but also to a relatively easy way to predict catalytic properties in these systems. Using an extended, customized valence force field several new derivatives of 1 have been tested. Their predicted and experimentally determined catalytic properties are in good agreement. The X-ray structures of the phenyl-substituted, monomeric azaphospholene 13, which hitherto results in the second best catalyst, and of its precursor 19 are presented.

The Hydrovinylation Reaction: A New Highly Selective Protocol Amenable to Asymmetric Catalysis

“…The hydrovinylation reaction has a long history − and, as early as 1988, Wilke cited unpublished results of an asymmetric hydrovinylation of styrene in the presence of allyl nickel halide, EtAlCl 2 and an esoteric azaphospholene ligand ( 1 ) . Subsequent work directed at simplifying the ligand structure 7 has shown that the original system is narrow in scope and is possibly of limited value for the development of a broadly applicable hydrovinylation reaction.…”

Metal catalysed hydrovinylation

“…Other diastereomers of the ligand and ''simplified'' monomeric versions of it have been found to produce very poor catalytic systems. 33 The results obtained with Wilke's ligand were the best in hydrovinylation for many years. 4 But at the end of the decade of 1990, new protocols avoiding the use of the problematic organoaluminium reagents and new ligands capable of inducing exceptional activities and enantioselectivities began to be developed.…”

In Pursuit of an Ideal Carbon-Carbon Bond-Forming Reaction: Development and Applications of the Hydrovinylation of Olefins

“…One other congener of this compound, the diastereomer ( RS )- 7 (prepared from (-)-( R )-myrtenal and (-)-( S )-1-phenylethylamine) is much less active and selective for the hydrovinylation of styrene. Monomeric and structurally related versions of this ligand have been prepared4c,21 in an attempt to simplify the synthesis and it has been found that catalytic activity and enantioselectivity invariably fall below useful levels.…”

“…Both the Wilke conditions19 using the azaphospholene ligand (RR)- 7 (Figure 2 and eq 12), and the use of a catalyst from aminophosphine phosphinite/Ni(COD) 2 /Et 2 AlCl,60 reported for 1,3-cyclohexadiene (eq 26), are limited either by the esoteric nature of the azaphospholene ligand, which permits no structural simplifications,21 and/or by the constraints imposed by the need for a strong Lewis acid like EtAlCl 2 . The isomerization of the product 1,4-diene at higher conversion could be one of the limitations of a recently reported non-asymmetric Ru-catalyzed reaction (eq 37).…”

“…Although the asymmetric hydrovinylation of cycloocta-1,3-diene (Scheme 15) is one of the earliest reported metal-catalyzed asymmetric carbon-carbon bond-forming reactions, 11a,59 no satisfactory solution to the problem of the hydrovinylation of 1,3-dienes emerged until 2006. 1 Both the Wilke conditions, 19 using azaphospholene ligand (R,R)-7 (Figure 2 and Scheme 7), and the use of a catalyst derived from an AMPP ligand (with [Ni(cod) 2 ] and Et 2 AlCl), 29 reported for cyclohexa-1,3-diene (Scheme 16), are limited either by the esoteric nature of the azaphospholene ligand, which permits no structural simplifications, 21 and/or by the constraints imposed by the need for a strong Lewis acid. The isomerization of the 1,4diene product at higher conversion could be one of the limitations of a more-recently reported non-asymmetric ruthenium-catalyzed reaction (Scheme 29).…”