Chiral Phosphites and Phosphoramidites Based on the Tropane Skeleton and Their Application in Catalysis

The Chemical Synthesis and Applications of Tropane Alkaloids

Tropanes are an important class of alkaloid natural products that are found in plants all over the world. These compounds can exhibit significant biological activity and are among the oldest known medicines. In the early 19th century, tropanes were isolated, characterized, and synthesized by notable chemical researchers. Their significant biological activities have inspired tremendous research efforts toward their synthesis and the elucidation of their pharmacological activity both in academia and in industry. In this chapter, which addresses the developments in this field since 1994, the focus is on the synthesis of these compounds, and several examples of sophisticated synthetic protocols involving both asymmetric and catalytic approaches are described. In addition, the structures of more than 100 new alkaloids are included as well as the applications and pharmacological properties of some tropane alkaloids.

Asymmetric Rh-catalyzed hydrogenation using a furanoside phosphite-phosphoroamidite and diphosphoroamidite ligand library

A furanoside phosphite-phosphoroamidite and diphosphoroamidite ligand library L1-L5a-f was tested in the asymmetric Rh-catalyzed hydrogenation of α,β-unsaturated carboxylic acid derivatives and enamides. Enantioselectivity depended strongly on the ligand parameters. High enantioselectivities were obtained in the reduction of dimethyl itaconate (up to >99% ee), α-dehydroamino acid esters (up to 99% ee) and several enamides (up to 92% ee). Kinetic and NMR studies on the intermediates of the catalytic cycle of the reaction indicate that the [Rh(P(1)-P(2))(substrate)](+) species is the resting state of the reaction and that the rate dependence is first order in rhodium and hydrogen pressure and zeroth order in the substrate.

Phosphoramidites: privileged ligands in asymmetric catalysis

Asymmetric catalysis with transition-metal complexes is the basis for a vast array of stereoselective transformations and has changed the face of modern synthetic chemistry. Key to this success has been the design of chiral ligands to control the regio-, diastereo-, and enantioselectivity. Phosphoramidites have emerged as a highly versatile and readily accessible class of chiral ligands. Their modular structure enables the formation of ligand libraries and easy fine-tuning for a specific catalytic reaction. Phosphoramidites frequently show exceptional levels of stereocontrol, and their monodentate nature is essential in combinatorial catalysis, where a ligand-mixture approach is used. In this Review, recent developments in asymmetric catalysis with phosphoramidites used as ligands are discussed, with a focus on the formation of carbon-carbon and carbon-heteroatom bonds.

Recent advances in enantioselective copper-catalyzed 1,4-addition

A comprehensive overview of recent literature from 2003 concerning advances in enantioselective copper catalysed 1,4-addition of organometallic reagents to alpha,beta-unsaturated compounds is given in this critical review. About 200 ligands and catalysts are presented, with a focus on stereoselectivities, catalyst loading, ligand structure and substrate scope. A major part is devoted to trapping and tandem reactions and a variety of recent synthetic applications are used to illustrate the practicality and current state of the art of 1,4-addition of organometallic reagents. Finally several mechanistic studies are discussed (162 references).