Iridium-Catalyzed Enantioselective Hydrogenation of α,β-Unsaturated Carboxylic Acids

Abstract

A highly efficient iridium-catalyzed hydrogenation of alpha,beta-unsaturated carboxylic acids has been developed by using chiral spiro-phosphino-oxazoline ligands, affording alpha-substituted chiral carboxylic acids in exceptionally high enantioselectivities and reactivities.

Asymmetric Hydrogenation of Olefins Using Chiral Crabtree-type Catalysts: Scope and Limitations

“…145 The catalytic system tolerated the variation of the ether-group but more importantly, the β-substituent could be changed from Ph to Me to H while retaining good enantioselectivity. 123 The successful asymmetric hydrogenations of crotonic-and cinnamicacid derivatives using iridium catalysts based on the spirocyclic oxazoline backbones prompted further expansion of the substrate scope.…”

Kupferkatalysierte Azid‐Alkin‐Cycloadditionen: regioselektive Synthese von 1,4,5‐trisubstituierten 1,2,3‐Triazolen

“…7, Schema 1) [6] [5] in Form einer Eintopfsynthese. [10] Hierbei wurde eine Kombination von CuI und NBS (N-Bromsuccinimid) verwendet, um in situ ein reaktives Iodoniumion zum Abfangen des Cuprat-Triazol-Intermediats (7, Schema 1) zu generieren. Diese verbesserte Vorschrift führt im Allgemeinen zu höheren Ausbeuten und kürzeren Reaktionszeiten, erfordert aber immer noch eine äquimolare Menge an CuI.…”

Iridium‐Catalyzed Highly Enantioselective Hydrogenation of Exocyclic α,β‐Unsaturated Carbonyl Compounds

“…The most straightforward and simplest approach to these compounds would be asymmetric hydrogenation of cyclic a,b-unsaturated carbonyl compounds but much less efforts have been focused on this option. [4,5] In most recent years, iridium complexes with chiral phosphine-oxazoline ligands have attracted much attention because of their easy availability and high reactivity and enantioselectivity in the hydrogenation of unfunctionalized olefins [6] or olefin substrates with less strongly coordinating groups [7][8][9][10] . In this context, Zhou found that the C=C bond of an a,b-unsaturated carboxylic acid could be hydrogenated with high enantioselectivity by using an iridium spirophosphine-oxazoline (SIPHOX) complex; [8] Bolm and Hou found that the C=C bond of a,b-unsaturated ketones can be hydrogenated with high enantioselectivity by using an iridium phosphineoxazoline (PHOX) complex; [9] Hou further investigated the enantioselective hydrogenation of a,b-unsaturated amides by using an iridium complex derived from ferrocenylphosphine-oxazoline (Fc-PHOX).…”

“…[4,5] In most recent years, iridium complexes with chiral phosphine-oxazoline ligands have attracted much attention because of their easy availability and high reactivity and enantioselectivity in the hydrogenation of unfunctionalized olefins [6] or olefin substrates with less strongly coordinating groups [7][8][9][10] . In this context, Zhou found that the C=C bond of an a,b-unsaturated carboxylic acid could be hydrogenated with high enantioselectivity by using an iridium spirophosphine-oxazoline (SIPHOX) complex; [8] Bolm and Hou found that the C=C bond of a,b-unsaturated ketones can be hydrogenated with high enantioselectivity by using an iridium phosphineoxazoline (PHOX) complex; [9] Hou further investigated the enantioselective hydrogenation of a,b-unsaturated amides by using an iridium complex derived from ferrocenylphosphine-oxazoline (Fc-PHOX).[10]However, there are few examples focused on the establishment of a-chiral carbon centers of cyclic carbonyl compounds, especially for lactones and lactams, via asymmetric hydrogenation. [4,9] Even in these limited examples, the asymmetric hydrogenation is strongly substrate dependent and there is no general solution for different kinds of cyclic substrates.…”