Asymmetric Carbonylations

Abstract

Transition metal -catalyzed carbonylation is one of the most straightforward tools to obtain fi ne chemicals intermediates from alkenes and other unsaturated products. Together with asymmetric hydrogenation, asymmetric C -C bond formation, and asymmetric allylic substitutions, the asymmetric carbonylations are among the most challenging homogeneous processes. Their potential is still to be made the most of, perhaps because of the complexity of these reactions where aldehydes, esters, or acids can be formed from simple olefi ns and enantiomerically pure products or enantiomeric enrichment of one of the products can be obtained when the transition metal catalyst is modifi ed with a chiral ligand. The most famous asymmetric carbonylation process is the Rh -catalyzed hydroformylation of alkenes, together with the Pd -catalyzed hydroxy -or alkoxycarbonylation of alkenes. There are, however, important differences between these processes, as the rhodium -catalyzed hydroformylation is of greater industrial interest than the palladium carbonylations. From the mechanistic point of view, rhodiumcatalyzed hydroformylation has been much more studied and understood than the palladium -catalyzed carbonylations maybe because of the stability of rhodium species, as well as the applicability of spectroscopic high -pressure (HP) nuclear magnetic resonance (NMR) techniques for the study of the intermediates and the early application of rhodium hydroformylation in industry as " oxo " process. As a result, the last developments in rhodium -catalyzed hydroformylation led to a very good control of the regioselectivity to the desired product as well as the preparation of practically enantiomerically pure aldehydes. Palladium -catalyzed carbonylations, both alkoxycarbonylation and hydroxycarbonylation, have also been widely studied but present more issues to obtain Catalytic Asymmetric Synthesis, Third Edition, Edited by Iwao Ojima

Applied Hydroformylation

“…Isoregioselective hydroformylation of olefins, with the exception of propene, produces chiral aldehydes . When the reaction is carried out with stereoface control, products with considerable potential for the production of chiral fine chemicals are formed.…”

Hydroaminomethylation of Styrene Catalyzed by Rhodium Complexes Containing Chiral Diphosphine Ligands and Mechanistic Studies: Why Is There a Lack of Asymmetric Induction?

“…The ligand donor/acceptor properties required seem to be opposite to get a good activity for each step of the tandem process. It is well-known that the more π-acceptor the phosphine ligand is, the more efficient is the hydroformylation reaction. ,, In this case, the electron-withdrawing character of the ligand plays a crucial role for the system activity, since the alkene double bond coordination as well as the migratory CO insertion are favored by an electrophilic metal center. On the other hand, the necessary σ-donor properties of the diphosphine ligand involved in the carbon–carbon double bond hydrogenation are often highlighted .…”

Progress on transition metal catalyzed asymmetric hydroesterification, hydrocarboxylation, and hydroamidation reactions of olefins

“…Asymmetric hydrocarbonylation has received attention for the last 5 decades. 10 c –12 While developing such a process has proven to be highly challenging due to the difficulty in achieving both regio- and enantioselectivity simultaneously, significant progress has been made particularly in recent years. This review will provide a brief overview of the development in this area.…”