Ligands for Practical Rhodium-Catalyzed Asymmetric Hydroformylation

Abstract

A series of bis-phosphite and bis-phosphine ligands for asymmetric hydroformylation reactions has been evaluated. Bis-phosphite ligands lead, in general, to high regioselectivities across a range of substrates while good enantioselectivities are limited to only a few examples. We found that bis-phospholane-type ligands, such as bis-diazaphospholanes and bis-phospholanes, can lead to very high regio- and enantioselectivities for several different substrates.

Highly Efficient Rhodium Catalysts for the Asymmetric Hydroformylation of Vinyl and Allyl Ethers using C1‐Symmetrical Diphosphite Ligands

“…For this purpose, asymmetric hydroformylation is a challenging transition metalcatalysed process that is of special interest. [1][2][3][4] Rhodium catalysts modified with phosphorus ligands are the most successful catalytic systems in the asymmetric hydroformylation reaction, [5] and phosphites are among the ligands that provided the best results. [6][7][8][9][10][11][12] Phosphites are very versatile ligands due to the straightforwardness of their synthesis from chiral diols and the ease of modifying the bisphenol moiety.…”

A Direct Route to Bifunctional Aldehyde Derivatives via Self‐ and Cross‐Metathesis of Unsaturated Aldehydes

“…

The aldehyde functionality, which is often reached in industry via hydroformylation of alkenes, [1][2][3] allows access to a large variety of functional compounds not only via classical organic synthesis but also by selective catalytic transformations, such as acylation reactions of alkenes and alkynes, [4] and direct access to esters, [5] lactones, [6] or propargyl derivatives. [7] Over the last decade, alkene metathesis catalysis has introduced a revolution in CÀC bond making strategies and has imposed itself as one of the most powerful synthetic reactions.

[8] Initiated by the discovery of the Grubbs catalyst, [9] the structurally well-defined homogeneous ruthenium alkylidenes [10] and indenylidenes [11] catalysts, which have the advantage of tolerating a large variety of functional groups, have made the olefin metathesis reaction practically attractive.

The alkene metathesis has already been applied to selective transformations of renewable materials originating from plant oils, [12] such as the ethenolysis and butenolysis of oleic acid derivatives [13] and the cross-metathesis of linear unsaturated esters with acrylates, [14] allylchlorides, [15] and even acrylonitrile [16] to generate linear a, w-bifunctional acid derivatives.

…”

Asymmetric Hydroformylation

“…In contrast, ligands 21i and 25g, which form mixtures of complexes, lead to low enantioselectivities [37- 39,42]. The ligand 21a was also evaluated in the Rh-catalyzed asymmetric hydroformylation of allyl cyanide 1b and vinyl acetate 1c but low to moderate enantioselectivities (13% and 58%, respectively) were obtained with these substrates [6].…”

“…In 2003, De Vries and co-workers reported the first Rh-catalyzed asymmetric hydroformylation of allyl cyanide and, although moderate regioselectivity was obtained (72%), the highest enantioselectivity (66%) by far was achieved using the ligand 40 [64]. As a general rule, the presence of electron-withdrawing substituents such as phenyl or heteroatoms in the alkene substrate leads to a control the regioselectivity in favor of the branched product, independently of the ligand used [6].…”

“…The hydroformylation of alkenes, which was originally discovered by Otto Roelen in 1938 [1][2][3], is nowadays one of the most important industrial applications of homogeneous catalysis [4][5][6][7][8][9][10][11][12]. However, the potential of this process in fine chemicals production is still to be exploited.…”